Note: Descriptions are shown in the official language in which they were submitted.
Wo95/15586 2 1 776 1 8 PCT~593/11698
.
--I
BATTERY ELECTROLYTE CnRCULATION SYjTEM
r ~
This invention relates to the ~ of a flooded electrolyte storage battery that facilitatw
the -ar~ ~ t, circulation, and '_ of the baKeq electrolyte amd also relatw to a procws
for charging such baKeries.
r~ T
Although there has been '' '- effort spent ~ . wL~;4fl g alternative rl ~ I"J. a - ~1
systems, the flooded electrolyte lead-acid battery is still the baKery of choice for general purposw
such as starting a vehicle, boat or airplane engine, emergency lighting, electric vehicle motive power,
energy buffer storage for solar-electric energy, and field hardware, both industrial amd military.
These batteriw may be periodically charged from a generator or other source of suitable DC power.
Historically, the electric power for such applications has been provided by W..~w.iu..dl
lead-acid baneries. The w.. ~ Iead-acid battery is a multi-cell structure, each cell generally
comprising a set of vertical ~ li" ' monopolar positive and negative platw formed of lead or
lead-alloy grids containing layers of el_,L-- ~ ~Iy active pastes or active materials. The paste
on the positive electrode plate when charged comprisw lead dioxide (PbO~), which is the positive
active material, and the negative plate contains a negative active material such as sponge lead. An
acid electrolyte based on sulfuric acid is interposed between the positive amd negative plates. The acid
electrolyte, in effect, is a third active material in each cell of a lead acid battery amd it, like the lead
oxide anodic active material and the sponge lead cathodic active material, is reversibly changed during
discharge of such a battery.
Bipolar batteriw have rec~w-tly gained attention and may serve to replace the use of the
w ._.1~iU~lGi baKery in such applications due to their inherently decreased size and weight. Bipolar
battery ( u -- ~ comprisw a seriew of electrode platw that each contain a negative active materlal
on one side and a positive active material on the other side, hence the terms rbipolar" and ~biplate~ .
The biplates are serially arranged in such a fashion that the positive side of one plate ls dlrected
toward the negative side of an adjacent plate. The bipolar baKery is made up of separate electrolytic
cells that are defined by biplate surfacew of opposing polaritiw. The biplates must be impervious to
electrolyte amd be electrically conductive to provide a serial electrical connection between cells.
Both ~ iul~al and bipolar lead acid baKeriw are ,~ ~ ;, .1 by a seriw of electrolytlc
cells. During the charglng of these baKeries, as well as through normal discharge, the water
component of the electrolyte contained in each electrolytic cell is converted by electrolysis to form
~ 35 hydrogen gas and oxygen. The ~ . l;- of some forms of these batteries permits the release of
these gasw by venting them to the atmosphere. Other forms of thwe batteriw are vaive regulated and
are constructed so as to facilitate both the ~ ~ ~ of the o~ygen gas and its ~ ~ into
the electrolyte solution. The electrolysis of the electrolyte during the charging of a vented battery
produce a loss in the water constituent of the acid electrolyte, thereby causing the of
that acid and its specific gravity to increase and the liquid level to drop. Ideaiiy, the
and specific gravity of a fully-charged flooded electrolyte lead-acid battery should be within a
WO9S/15586 2 1 7 7 6 ~ 8 PCT/US93/11698
relatively narrow range of values for which the batteq has been designed. ~n acid electrolyte of too-
low produces a decrease in battery p, r ~ while an acid electrolyte of too-high
decreases the useful life of the battery and also reduces battery discharge p,
Therefore, in batteries where water loss can occur, it is necessary to periodically add water to the
electrolyte to replenish the volume of electrolyte in the battery and to bring the specific gravity of the
electrolyte into the design range from a too-high value. In order to permit the volumetric
~' ' of the electrolyte, these batteries are typically constructed with a sealable opening at
each cell which e~ctends to an outside top surface of the battery. Al ' _'y, the user can replenish
the electrolyte volume in each cell by adding water tbrough each cell opening.
The technique of , ' ~ ' ~ a battery electrolyte by adding water to each individual cell can
be a dangerous, messy, time consuming, and inaccurate operation. When the user removes the cap
of each cell during the l~ . ' ' operation, the user is e cposed to both the battery electrolyte and
the gases. The battery electrolyte is e~tremcly acidic, and may cause burns to slcin or permanent
damage to clothmg and the like. Therefore, contact by the user is to be avoided. ,~ ' " "~" the
gases produced during the chargmg or discharge of the battery is largely hydrogen which may be
e~plosive under certain conditions.
During the ,' ' operation it is not uncommon for the water being used to fill the
battery electrolytic cell, to spill onto the surface of the battery or onto the user. The dangers
associated with coming into contact with acidtc battery electrolyte has already been described.
However, when water is used to replenish the electrolytic cell the spilled watcr will oftentimes
combine with ' electrolyte on the surface to form an acidic solution. The clean up of this
spilled water may place the user in contact with the acidic solution, posing a risk of injury to the wer.
Additionally, improper watering practices, such as adding water to the electrolytic cells in a
discharged battery, may result in electrolyte ~flooding~, due to the imcrease in electrolyte volume
associated with the charging of the battery, again posimg a risk to the user.
R ~ ' ' ,, each individual electrolytic cell with the proper amoumt of electrolyte is a matter
of the user's judgement and requires that tbe user repeat the process of adding water and visually
chec3~ing the level in each cell until the proper level is achieved. During the charging operation, the
technique of visually checkmg the electrolyte level in each cell may pose a risk of electrolyte conUct
to the user due to generation of effervescent electrolyte caused by the gassing or electrolysis reaction
of the water component of the electrolyte.
The of ~ ._,.li~,~ and bipolar flooded electrolyte batteries also restricts the
circulation and mi~cing of tbe banery electrolyte within each cell during the charging operation.
Mi~ing of the electrolyte is import;mt in order to ensure that each electrolytic cell comprises a
1~ volume of electrolyte having a uniform specific gravity. Specific gravity is a measure
the ability of the desired electrolyte to participate in the il ' ' reaction. A~ , an
electrolytic cell having a ~ O electrolyte of selected volume and specific gravity is desirable
because it will necessarily render an optimal amount of electrical energy and power and assure long
life.
In . ' and bipolar electrolyte batteries, the agiUtion and miking of electrolyte in each
CA 02177618 lsss-03-ol
wo 95/15586 PCTIUS93/l 1698
cell during the el~ g operation is accomplished by passing an amount of current usually measured
as ampere-hours into the battery in e~ccess of that required to restore the voltage capacity of the
particular battery. This u~hdion is referred to as ~overcharging~ the battery. During a normal
charging opc~diùn, a current is passed into the battery for the purpose of ~ g the active
m~Pri~lc within the battery. The applied current reverses the ele_hoc~ ;r~l reaction ,~onc~ e
for the prod~lrtinn of electrihal energy during the pluc~ ;ug ~ ch~ge cycle, causing the
,~con~ n of the active .--~ c As the charging OpC,.diOII pluceeds, the active m -Priql will
contimlP to be l~n~ d until the voltage and capaciq of the battery is fully re tored at which time
the battery is said to be co~rletPIy charged.
The ~ l;l;on~l current passed into the battery after it has been fu11y charged and l~or~ n
of the cell active materials (i.e., during the o.e.~ge operation) no longer causes the reversal of the
de~ho~h~ reaction and rccQ~ ~ of the cell active In''-PriqlC~ but will instead cause the water
cc.- ~~ 1 of the electrolyte to dectrolyze. The dc~,hul~ . of the de~hul~llte causes the gas plodu.
of that process ~dlog_~ and o~cygen) to migrate through the volume of electrolyte as free bubbles
rising to the surface of each dectrolytic cdl. The l.. u.~e.~l of the ele. hul~i,is gas bubbles through
the electrolyte volume serves to agitate and mLlc the cle~hul~le within each de.,l-ul~lic cell. As the
u~ .L~,~, Opf ~ ;h-- a '-'1 ;~ C, the a6;~ of the cle~ llol~ s gas bubbles plU lu~.e~c a hu~-lGg~.~uS
volume of dectrolyte having a uniform specific gravity. An ele~ul~lè volume having a uniform
specific gravity is ~ e because it serves to .---~ the de~l,;cal enerD storage pot~ l and
life of each de~ul~Lic cdl. However, the operation of overcharging the battery in order to achieve
a h~...og~ volume of de~,~ol~te generates heat and cûlluSiOn of the positive current c~llec~r
which ~hol~ the life of the battery, i..~e&s~c the need for de~ulyte rep1~ -;Dl ---r ~1 h..~eases the
time and e~e~ic-1 energy C4-- ~ in charging the battery, and is o;oAr~ 11y inPffirjPn-
It is therefore seen that a need e~cists for a flooded ele~ te battery (~..~ , bipolar or
otherwise) which is ~o~t~u~ to r ~~ the ~ ~r ~1 repl~ 1 of battery de~l~ul~le in a
manner that is not d~g~u~, messy, or time consuming and perrnits the user to easily and ~
~len;~1 each ele~hul~c cell with the correct amount of de~llùl~le having the correct specific
gravity.
A need e~ists for a flooded decl.ùl~t;c battery (conventional, bipolar or otherwise) which is
co~LIu~.~d to f~~i1jt~-P the mi~ing and ~, ~geu~ ~;o ~ of the battery e~ ùl~te within each cell in
a manner that avoids the need to u.~.ha~ge the battery, and thus e~ s the adverse affects
~ccoci~-ed with the u.~ h u6~ operation.
. .....
CA 02l776l8 l999-03-Ol
- 3A -
Summary of the Invention
According to the invention, there is provided a flooded
electrolyte seco~Ary storage battery which comprises: a plurality
of cells having coplanar tops and coplanar bottoms; an electrolyte
transport rhAnnel ext~n~ing substantially vertically in each cell
from an upper end proximate the cell top to a lower end proximate
the cell bottom; a gas and liquid inlet port into a top portion of a
first one of the cells for discharging liquid introduced thereinto
to an upper end of the transport ~hAn~el in that cell; fluid carry-
over passages connecting the first cell, a last one of the cells and
all ~ -ining cells of the plurality, each carry-over passage having
an inlet end at a selected level in the cell in which the inlet is
located and an outlet end in a different cell at a location selected
for discharging liquid flowing through the outlet end to the
transport rhAnnel in that different cell, each carry-over passage
being in~p~n~nt of each other one and r lnicating between only
two cells; and a gas and liquid outlet port to the exterior of the
battery from the top portion of the last cell, the outlet port
having an entry opening at a selected level in the last cell, the
selected level in each cell being at or below the upper end of the
transport ~hAnnel for that cell.
According to a further aspect of the invention, there is
provided a system for replenishing and circulating electrolyte in a
liquid electrolyte secondary battery, the system comprising: an
electrolyte transport rhAn~e1 ext n~ing vertically in each of a
plurality of electrolytic cells from an inlet end near a top of the
cell to an outlet end near a bottom of the cell, the tops and
bottoms of all cells being coplanar with one another; an inlet port
exten~ing from a position outside a battery to a position within a
first one of the electrolytic cells; an outlet port ext~n~ing from a
position within a last one of the electrolytic cells to a position
outside the battery; a fluid carry-over passage ext~n~ing between
and hydraulically connecting the upper ends of each adjacent set of
cells and providing a portion of a serial fluid flow path from the
first cell to the last cell via all other cells, each transport
~hAnnel receiving
CA 02177618 1999-03-ol
- 3B -
electrolyte intro~llceA to its cell via the respective one of the
inlet port and the carry-over passages, each carry-over passage
being in~p~n~nt of each other carry-over passage and c ln;cating
between only two cells; and means for intro~1lcing an electrolyte
solution into the inlet port.
According to a further aspect of the invention, there is
provided an electrolyte replenishing and circulation system
comprising; an inlet port comprising a passage ext~n~ing from a
location outside an electrolyte battery, through an upper cell
boundary, and into a first electrolytic cell; an outlet port
comprising a passage ext~ing from a position within a last
electrolytic cell through the upper cell boundary, to a position
outside of the battery; a plurality of transport ~h~nn~ls, each
transport ~h~nnel exten~ing vertically in each electrolytic cell,
each transport ch~nnel comprising a flared portion at one end near
the top of the cell and a ~h~n~el op~ning near a bottom of the cell;
a plurality of carry-over passages, each carry-over passage having
an inlet end and an outlet end, the inlet end and outlet end of each
carry-over passage ext~n~ing through the upper cell boundary and
into adjacent electrolytic cells to hydraulically connect each cell,
each transport ~h~nn~l receiving electrolyte introduced to its cell
via the respective one of the inlet port and the carry-over
passages, the position of the inlet end of the carry-over passage
within each electrolytic cell defining a working electrolyte level
in the cell; and means for intro~l~cing an electrolyte solution into
the electrolyte battery.
According to still yet a further aspect of the invention,
there is provided a method for establishing working levels of liquid
electrolyte in each of the cells of a multi-cell liquid electrolyte
storage battery, the method comprising the steps of: providing in
each cell a fluid flow passage exten~ing from an upper end above a
working cell electrolyte level to an open lower end proximate a
bottom of the cell; providing fluid flow interconnections between
all of the cells each of which interconnections has an inlet at the
working level in one of two cells interconnected by it and an outlet
associated with the upper end of the flow passage in the other cell
interconnected by it, each cell being gas-tight except for the flow
interconnection from it;
~ . . . ~ . . ..
CA 02l776l8 l999-03-Ol
- 3C -
pumping electrolyte into a first one of the cells to the flow
passage in the first cell and from the first cell to a last cell via
the flow interconnections and from the last cell through an outlet
having an entrance op~ning at the working level in the last cell to
fill each cell with electrolyte at least to the working level in
each cell; and pumping air into the inlet and through the several
cells to the outlet to adjust the electrolyte level in each cell to
the working level in each cell.
According to still yet a further aspect of the invention,
there is provided a method for replenishing and circulating
electrolyte through electrolytic cells of a liquid electrolyte
sero~Ary battery, the method comprising the steps of: introAllcing
an electrolyte solution into a first electrolytic cell of the
battery; hydraulically transporting the electrolyte solution through
the first electrolytic cell via intercell flow passages to a
plurality of hydraulically serially connected electrolytic cells
that are coplanar with one another until each cell is filled;
circulating the electrolyte through the plurality of electrolytic
cells; and adjusting the level of electrolyte solution in each
electrolytic cell to a working level by circulating air through each
of the electrolytic cells via the intercell flow passages.
According to yet a further aspect of the invention, there is
provided a flooded electrolyte secondary battery which includes a
plurality of cells each having a top and a bottom, and a
substantially planar cover closing the tops of the cells, the
battery comprising: an electrolyte transport rhAnne1 ext~n~ing
substantially vertically in each cell from an upper end proximate
the cover to a lower end proximate the cell bottom; a gas and liquid
inlet port ext~n~ing from outside of the battery through the cover
into a top portion of a first one of the cells for discharging
liquid introduced thereinto to an upper end of the transport
in that cell; carry-over passages connecting the first cell, a last
one of the cells and all ,~ -ining cells of the plurality in series
liquid flow relation, each carry-over passage having an inlet end at
a selected level in the cell in which the inlet is located and an
outlet end in a different cell, wherein the inlet end for each
carry-over passage is below its outlet end, and wherein
. , .
CA 02177618 1999-04-06
-- 4
the outlet end of each carry-over passage is at a location
selected for discharging liquid flowing through the outlet
end to the transport ch~nn~l in that different cell; and a
gas and liquid outlet port ext~nrli ng from outside of the
battery through the cover to the top portion of the last
cell, the outlet port having an entry opening at a
selected level in the last cell, the selected level in
each cell being at or below the upper end of the transport
ch~nnel for that cell.
According to a further aspect of the invention, there
is provided a method for charging a liquid electrolyte
secondary battery, the method comprising the steps of:
introducing an electrical current into the battery;
circulating the electrolyte serially through electrolytic
cells of the battery during at ]east during a terminal
portion of the charging process, and equalizing the level
of electrolyte in each electrolytic cell by serial air
movement through the cells.
Brief Description of the Drawinqs
The above-mentioned and other features of this
invention are set forth in the i.ollowing detailed
description of the presently preferred and other
embodiments of the invention, which description is
presented with reference to the accompanying drawings
wherein:
FIGS. 1,5,6 and 7 are cross-sectional elevation views
of a preferred embodiment of a ~Elooded
CA 02177618 1999-04-06
electrolyte battery, constructed to facilitate the
replenishment and circulation oi battery electrolyte, at
successive stages in practice oi the procedural aspects of
this invention; more specifical]y,
FIG. 1 illustrates commencement of an electrolyte
replenishment operation;
FIG. 2 is a cross-section view taken along line 2-2
in FIG l;
FIG. 3 is a cross-section view taken along line 3-3
in FIG. l;
FIG. 4 is a fragmentary cross-sectional elevation
view of an exemplary bipolar balttery according to the
present invention;
FIG. 5 illustrates the states of the electrolytic
cells at the end of the electro:Lyte pumping phase of the
procedure;
FIG. 6 shows an initial stage of the cell levelling
phase of the procedure;
FIG. 7 shows the battery a:Eter the electrolyte in
each electrolytic cell has been levelled;
FIG. 8 is a schematic diag:ram of an embodiment of a
electrolyte conditioning, replenishment and circulation
system;
FIG. 9 is a graph that describes the electrolyte
condition in a test battery at ,~ifferent times during a
charging operation where the el,ectrolyte is circulated
according to principles of this invention; and
FIG. 10 iS a schematic diagram of a charging
apparatus useful to implement the procedural aspects of
this invention.
Detailed Description
The need to conserve resources and reduce pollution
CA 02177618 1999-04-06
- 5A -
directs attention to the electrolyte battery as a
desirable alternative to internal combustion engines and
power source for an automobile. However for the public
to adopt battery powered vehicles their use and
maintenance must be at least as convenient as the
hydrocarbon powered vehicles that they are replacing. For
example apart from reducing air pollution there is
little incentive for an automobile owner to give up a
gasoline fuelled automobile in i-avour of a battery powered
automobile when the battery powered automobile is less
convenient and more costly to maintain.
The principal costs associated with owning a battery
powered automobile apart from lthe initial purchase cost
is the cost of recharging serv:icing and eventually
replacing the battery or batter:ies. Electrolyte
batteries conventional or bipo:Lar lead-acid or other
all have a limited life that is dependent on the materials
used within the battery and upon their ability to
participate in the electrochemical reactions that produce
electricity. To m~Yimize the useful life of electrolyte
batteries the user must at the very least recharge the
battery and replenish the batte:ry electrolyte that has
been lost during the electrochemical reactions which
produce and release electrical energy. Since the cost to
replace the battery or batteries used in an electric
automobile may be substantial it is highly desirable that
the useful life of the electrolyte battery be ~-Yimized
through improved charging and electrolyte replenishment
procedures that can be conveniently carried out by the
user.
This invention relates to methods and equipment for
maximizing the useful life of an electrolyte battery
conventional or bipolar that may be used in applications
such as the automobile. The inventive methods permit a
CA 02l776l8 l999-04-06
- 5B -
user to maximize the useful life of an electrolyte battery
in a manner that is convenient, cost effective, and will
remove the dangers and risks associated with battery
CA 02177618 1999-04-06
maintenance.
FIGS. 1-3 and 5-7 illustral:e, in simplified form, a
flooded electrolyte battery constructed according to
principles of this invention, and which, for purposes of
illustration and clarity, compr:ises four electrolytic
cells. It is, therefore, to be understood that the
principles of this invention apply to an electrolyte
battery comprising any plural number of electrolytic
cells. For purposes of reference, the uppermost portion
of the battery will hereafter be referred to as the top of
the battery and the bottommost portion of the battery will
hereafter be referred to as the bottom of the battery.
For purposes of definition, a f;looded battery as referred
to comprises any type of electrolyte battery that can be
characterized as having a plurality of electrodes immersed
in an electrolyte solution.
FIG. 1 shows a preferred embodiment of a flooded
electrolyte battery 10 according to principles of this
invention. Battery 10 comprises a number of electrolytic
cells 12 which each may comprise a number of electrically
conductive electrodes (not shown) and electrically non
conductive separators (not shown) immersed in an
electrolyte solution 14. The electrolyte solution may
include any type of liquid capable of participating
substantially with active materials disposed on each
electrode in an electrochemical reaction for producing
electricity. In lead-acid electrolyte batteries an
electrolyte comprising an aqueous sulphuric acid solution
is preferred. It is to be understood that the electrolyte
battery according to this invention may comprise a
CA 02177618 1999-04-06
- 6A -
conventional flooded monopolar battery, a flooded bipolar
battery (see FIG. 4), or any other type of flooded
electrolyte battery.
The electrolytic cells 12 of the battery are
physically separated from adjoining cells by cell
partitions 16 which extend vert:ically from the top of the
battery to the bottom of the battery. Each electrolytic
cell is bound on its top by a b.~ttery cover 18 which may
extend to cover and form a gas and electrolyte tight seal
across all of the cells in the ]battery. Each cell is
bounded on its bottom by a base 20 which may extend to
cover and form a seal across all of the cells at the
bottom of the battery. The cell partitions 16 are spaced
apart at preferably equidistant positions from each other
throughout the battery to form the series of preferably
equal volume cells 12.
An inlet port 22 extends from outside of the battery
12 through an inlet hole 24 in the battery cover 18 and
into a first cell 12-1. The inlet port may comprise an L-
shaped tube positioned with its horizontal portion located
outside of the battery and its vertical portion ext~n~i ng
into the battery. The inlet port comprises an inlet end
26 at an end outside of the battery, and an outlet end 28
at an opposite end within the first electrolytic cell 12-
1. The location of the inlet hole 24 preferably causes
the inlet port 22 to enter the cell 12-1 at a position
near a battery wall 32.
An electrolyte transport channel 30 extends
vertically along the battery wall 32 in the first
electrolyte cell 12-1, and other such chAnn~ls extend
vertically along a cell partition 16 or other cell wall in
each other cell 12. Each channel opens to its cell
adjacent the bottom of the cell. As shown in FIGS. 1 and
CA 02177618 1999-04-06
- 6B -
2, the transport rh~nnels 30 can be formed by a space
between a ~.h~nnel partition 34 and the battery wall 32, in
the first cell, and by spaces between a ch~nn~l partition
34 and a cell partition or wall in each other cell. In a
preferred embodiment, the channel partitions 34 can each
comprise a rectangular sheet (not shown) having a
horizontal dimension equal to the width of each
electrolytic cell parallel to w;~ll 32 and a vertical
dimension slightly shorter than the height of each cell.
The ~h~nn~l partitions may be m;~de from electrically
nonconductive materials that are
CA 02177618 1999-04-06
chemically resistant to the effect of the electrolyte and
may include polymeric materials such as polypropylene and
the like.
Each channel partition 34 preferably has a flared
upper end 36 which is positioned near the battery top
within each electrolytic cell. The flared end 36 forms a
wide inlet mouth in the ~hAnn~l 30 for directing into the
chAnn~l the liquid electrolyte ~which can be introduced
into the cell, as through the inlet port 22 or through a
carry-over passage 40. As shown in FIG. 3, each channel
partition defines a ~hAnnel outlet opening 38 at its
bottom end near the cell bottom. The channel outlet
op-~ni ng 38 may be formed either by a single slot op~n; ng
or by plural openings adjacent the cell bottom. ChAnn~
30 provides a passage for the flow of electrolyte
introduced into the top of the cell to an entry into the
cell adjacent the bottom of the cell through opening 38.
The position of each rhAnnel partition in preferably
parallel relation to either the battery wall or a cell
partition can be maintained by a number of vertical ribs
37 which can extend from the wall or partitions, as shown
in FIG. 2, or from the ~hAnn~l partition itself. If
present, the ribs subdivide the chAnnel into a plurality
of vertical electrolyte flow passages to the bottom of
each cell.
As shown in FIGS. 2 and 3, in a preferred embodiment,
each battery side wall enclosing the electrolytic cells
comprises at least one pair of ridges 39 per each cell.
The ridges are arranged to accommodate the thickness of
the ~hAnnel partition. Each partition is placed into
position within its cell to form the transport chAnn~l 30
CA 02177618 1999-04-06
- 7A -
by inserting the partition so that its vertical edges lie
between the ridges at each battery wall. Once in place,
the ridges restrict the movement: of the channel partition
and maintain its spaced paralle]L relationship with the
battery wall or cell partition.
The battery can be manufacl:ured by placing the
~hAnn~l partitions within each electrolytic cell before
the battery electrode plates are introduced. In order to
permit the passage of the batte:ey electrodes past the
flared portion of the rh~nnel paLrtition, the rh~nnel
partition may be constructed having a live hinge near the
flared portion to allow the flared portion to be moved
aside and out of the way to facilitate the electrode plate
installation. The flared portion can be an integral
member of the battery, molded into a permanent battery
element.
It is to be understood that the transport rhAnnel 30
can have a configuration other than that specifically
described and illustrated. For example, instead of being
formed between the ~h~nn~l partition and the battery wall
or cell partition, the transport ~h~nn~l may comprise a
tube that extends vertically from the battery cover into
the cell to an open lower end near the cell floor; see,
for example, FIG. 4 which illustrates the practice of this
invention in the context of a bipolar battery.
Each electrolytic cell 12 is hydraulically connected
at its upper end to the upper e!nd of an adjacent cell by
an electrolyte carry-over passage 40 or by an equivalent
duct in or in association with the upper boundary of the
electrolytic cell within the battery. Each carry-over
passage may comprise an inverted U-shaped tube having
CA 02177618 1999-04-06
- 7B -
substantially parallel legs, an inlet end 42 and an outlet
end 44. Each carry-over passage can extend from one cell
to an adjacent cell through a pair of carry-over passage
holes 46 located in the battery cover 18 as shown in Fig.
1. Alternatively, each carry-over passage may extend from
one cell to an adjacent cell through a carry-over passage
hole located in an upper portion of the cell partition 16.
The carry-over passage holes are located so that the
outlet end 44 of each carry-over passage is aligned with
the upper end of a transport ch:~nnel 30. In FIG. 1,
CA 02177618 1999-04-06
the carry-over passages 40 are shown having their inlet
ends 42 at greater distances be:Low the top of the cells
than their outlet ends 44. As discussed in detail below,
the location of the inlet end 4:2 from the highest part of
the carry-over passage is signi:Eicant because it defines
the electrolyte level in each e.lectrolytic cell 12 during
a levelling operation performed according to methods of
this invention. Additionally, the length of the outlet
end 44 of each carry-over passage is also significant
because it is desired that an air gap or headspace 48 be
maintained between the outlet end and the adjacent
transport rhAnnel opening. This air gap is important
because it facilitates low pressure replenishing and
levelling of the electrolyte in each cell according to
methods of this invention. The smaller the air gap, i.e.,
the smaller the air space in the electrolytic cell, the
lower the pressure associated with electrolyte
replenishing. The air gap 48 or opening in the liquid
flow path is not required but is preferred to reduce
liquid and air back pressure associated with the
electrolyte replenishment operation. This reduced back
pressure translates into reduce!d pump requirements and
simpler and safer acid transport.
An outlet port 50 extends vertically from a last
electrolytic cell 12-4, through an outlet hole 52 in the
battery cover 18. The outlet port may comprise an L-
shaped tube having an inlet encl 54 within the last cell
and an outlet end 56 outside oi. the battery. Like the
inlet end 42 of each carry-over passage 18, the length of
the inlet end of the outlet port 50 is important because
it defines the electrolyte level in the last electrolytic
cell during a levelling operation according to methods of
this invention.
CA 02l776l8 l999-04-06
- 8A -
The electrolytic cells in l_he flooded electrolyte
battery are completely sealed from the atmosphere except
for the existence of the inlet ~nd outlet ports. The
electrolytic cells 12 are completely sealed from each
other except for the cross-over passages 40 hydraulically
connecting them.
Bipolar batteries can also be constructed according
to practice of this invention. FIG. 4 shows a sectional
view of a bipolar battery 11 comprising several
electrolytic cells 12-1 through 12-N each defined by a
pair of bipolar electrode plates 19 or biplates . The
top portion of each of the cells making up the bipolar
battery is sealed from the atmosphere by a battery cover
18. The cover comprises at least one inlet port 22
ext~n~;~g through the cover frcm outside the battery into
a first cell 12-1. The inlet port 22 empties into an
electrolyte transport passage 31 positioned along an
adjacent electrode plate 19 ancl ext~n-l; ng downwardly into
the first cell. The transport passage 31 may comprise a
hollow tube or the like made from the same type of
electrically nonconductive and chemically inert materials
previously described for the tr.ansport channel partitions
34 in the embodiment illustrated in FIG. 1. The transport
passage comprises an air hole "7 near the top portion of
the cell that serves the same i-unction as the air gap 48
previously described in the e~odiment illustrated in FIG.
1. Alternatively the carry-over passages and transport
passage described in FIG. 4 may also be used in
conventional flooded electrolyte batteries such as that
described in FIGS. 1 5 6 and 7.
The cover 18 also comprises a number of carry-over
passages 40 which serves to hy~draulically interconnect
adjacent bipolar cells. Each carry-over passage comprises
an inlet end positioned near the top of each cell an
CA 02177618 1999-04-06
- 8B -
outlet end which empties into a transport passage 31 in an
adjacent cell,
CA 02177618 1999-04-06
the outlet end having an air ho:Le 47 near the cover. The
cover 18 also comprises at least one outlet port 50
extending from a position within a last cell 12-N, through
the cover to a position outside the bipolar battery.
Like the embodiment described in FIG. 1, the inlet
position for each carry-over passage 40 and the outlet
port is important because it serves to define the
electrolyte level in each electrolyte cell during a
levelling operation according to methods of this
invention. Additionally, the air hole 47 in each carry-
over passage is important because it serves to permit the
flow of air, during an air purge operation that will be
described in detail below, to remove electrolyte from the
carry-over passage. The remova.l of electrolyte from the
carry-over passages is desirable because electrolyte
rem~; n; ng inside the carry-over passages may cause the
interconnecting electrolytic cells to electrically short
circuit. Alternatively, instead of passing through the
battery cover 18, the carry-over passages 40 may be
configured to pass through a cell partition 16.
Although specifically described and illustrated in
FIG. 4, it is to be understood that other bipolar battery
configurations are within the ~;cope of this invention.
For example, the battery cover 18 may be configured so
that the portion of the carry-over passage connecting its
inlet end and outlet end compr:ises a ~h~nn~l along the top
surface of the battery cover. In this embodiment, the
carry-over passage may be formed by placing an
appropriately sized and configured cover over the ch~nnel
in the battery cover.
FIG. 1 shows a preferred embodiment of the
electrolyte battery according to principles of this
invention at a condition where the electrolyte level in
CA 02177618 1999-04-06
- 9A -
each electrolytic cell is low and in need of
replenishment, i.e., addition oE electrolyte to restore
desired electrolyte levels in tlhe several cells. The
electrolyte battery 10 constructed according to principles
of this invention permits replenishment of the electrolyte
in each of the cells to a predetermined or working level
by methods according to this invention.
The electrolyte 14 can be replenished by introducing
(as by use of pump 58 shown in FIG. 8) the desired
electrolyte or water solution into the inlet end 26 of the
inlet port 22, causing the electrolyte to flow through the
inlet port and into the first e!lectrolytic cell 12-1 as
shown in FIG. 1. The electroly~te exits the outlet end 28
of the inlet port 22 and empties into the electrolyte
transport chAnnel 30. The elec:trolyte flows vertically
down the depth of the transport: chAnn~l, out the chAn~el
outlet opening 38 near the bot1:om portion of the cell and
vertically upwards through the volume of the cell. The
level in the Eirst electrolyte cell rises as the
electrolyte is continuously introduced through the inlet
port.
Referring now to FIG. 5, .~s the electrolyte continues
to fill the first electrolytic cell 12-1, the electrolyte
level will begin to approach the inlet end 42 of a first
carry-over passage 40-1 which hydraulically connects the
first cell with a second adjacent cell 12-2. When the
electrolyte surface in cell 12-1 reaches the inlet end 42
of passage 40-1, the rising electrolyte surface begins to
compress the gas in the gas-tight upper end of the cell.
However, the pressure in adjacent cell 12-2 remains
substantially unchanged. The level of the electrolyte
surface in the inlet leg of passage 40-1 becomes higher
than the level of the electrolyte surface in cell 12-1
CA 02177618 1999-04-06
- 9B -
outside passage 40-1. As introduction of electrolyte into
cell 12-1 continues, the liquid level in passage 40-1
becomes sufficiently high that
.. , . , . ... ~
CA 02177618 1999-04-06
-- 10 --
electrolyte begins to flow through passage 40-1 into cell
12-2. At that point, the level of electrolyte in cell 12-
1 reaches a stable level between the upper end of
transport channel 30 and the level of the lower end of the
inlet leg of passage 40-1, and ~Eurther flow of electrolyte
into the battery then causes the level of the electrolyte
in cell 12-2 to rise. The process is repeated in sequence
in each of cells 12-2, 12-3 and 12-4 to cause each of
those cells to be filled to a s1able level in each cell at
a point above the carry-over passage inlet or inlet
opening to outlet port 50, as appropriate. Thereafter,
continued introduction of electrolyte into the battery via
inlet port 22 causes electrolyte to circulate through the
battery and out of outlet port 50, as shown in FIG. 5.
The level of electrolyte in cell 12-1 r~-ins
constant during filling of cell 12-2 until the level in
cell 12-2 reaches the inlet end of carry-over passage 40-
2. As the liquid level in cell 12-2 begins to rise to
compress gas in the top of that cell, the liquid level in
cell 12-1 also rises slightly. At the point where liquid
flow through passage 40-2 begins into cell 12-3, the level
in cell 12-2 will be at an elevation equal to the liquid
level in cell 12-1 during initial filling of cell 12-2,
and the level in cell 12-1 will be above that in cell 12-
2; that is true if, as preferrecl, the inlet ends of tube
40 and of outlet port 50 are all at a common level in the
battery. It will be seen, therefore, that upon filling of
the battery to a point where electrolyte flows through
outlet 50, the respective cell liquid levels in the
several cells will be as shown i.n FIG. 5 where the levels
are lower in the cells proceeding from first cell 12-1 to
last cell 12-4. The difference in electrolyte
... .
CA 02177618 1999-04-06
- lOA -
level for each cell is the inherent result of replenishing
the battery electrolyte using hydraulic principles which
depends upon a cumulative hydraulic pressure effect.
The pressure of electrolyte required at the inlet
port to achieve filling of the several cells to the stable
levels described above and shown in FIG. 5, is the sum of
the effective electrolyte columns in the inlet legs of the
several carry-over passages 40 and in the outlet port
above the electrolyte levels in the cells from which they
provide flow paths. That is a relatively low pressure
which follows from the dimensions of the structures and
arrangements present in the upper portions of the several
cells.
The ability to transport the electrolyte between
adjacent electrolytic cells by hydraulic principles
through the carry-over passages avoids the need for using
moving parts within each electrolytic cell, which
effectively eliminates the potential for failure
associated with such moving part:s.
The introduction of electrolyte into the first cell
may be terminated once the elect:rolyte is observed to be
exiting the battery through the outlet port 50 in the last
cell 12-4. Alternatively, the electrolyte exiting the
battery may be collected to permit its circulation and
reintroduction back into the first electrolytic cell.
After the battery has been charged to a predetermined
level and the electrolyte in the battery is completely
homogeneous the electrolyte replenishment and circulation
operation may be terminated. The electrolyte levels in
the several cells can be equalized to a predeter~ined
level by an air purge operation according to methods of
this invention. As shown in FIG. 6 air at a suitable
CA 02177618 1999-04-06
- lOB -
pressure is introduced into port: 22 and into the first
electrolytic cell 12-1. The air exits the outlet end 26
of the inlet port, and flows int:o the portion of cell 12-1
which is above the electrolyte surface in that cell. In
such flow, the air enters the top of the cell via air gap
48 which exists between the outlet end of the inlet port
and the top end of channel 30 in cell 12-1. The air does
not flow down
, . _ .
CA 02177618 1999-04-06
the rhAnnel and up through the electrolyte in the cell.
The air so introduced into cell 12-1 exerts pressure on
the surface of the electrolyte. This air pressure causes
the volume of electrolyte which lies above the inlet end
42 of carry-over passage 40-1 to be transported through
the carry-over passage and into the second adjacent
electrolytic cell 12-2. The electrolyte transport from
the first to the second cell continues until the level of
the electrolyte in the first cell drops to just below the
inlet end 26 of the carry-over passage 40-1, at which time
the air introduced into the first cell is transported
through the carry-over passage and into the second cell
12-2.
The volume of electrolyte entering the second cell
increases the head pressure of 1:he electrolyte in the
second cell causing the transport of the electrolyte
through the second carry-over passage 40-2 and into the
third cell 12-3 according to the same principles
previously described for the electrolyte replenishing
operation. Once the electrolyte level in the first cell
drops below the inlet end 26 of the carry-over passage 40-
1 and air begins to enter the second cell, that air enters
directly into the upper portion of the second cell and
exerts its pressure onto the surface of the electrolyte in
cell 12-2 causing the volume of electrolyte present above
the inlet end 26 of the second carry-over passage 40-2 to
continue to pass through the second carry-over passage and
into the third electrolytic cel]L 12-3. As in the first
cell, the electrolyte transport from the second to the
third cell will continue until 1he level of the
electrolyte in the second cell drops below the inlet end
26 of the second carry-over passage 40-2, at which time
the air introduced into the first cell and communicated
into the second cell is communicated through the second
carry-over passage 40-2 and into the third cell 12-3.
CA 02177618 1999-04-06
- llA -
The air pressure effects and events which occurred in
the first and second cells are repeated in succession in
third cell 12-3 and in last cel]. 12-4. Assuming, as is
preferred, that the openings to the carry-over passages 40
and to the outlet port 50 are located at a common
elevation in battery 10, the result of the air pumping
process is the condition shown in FIG. 7 where the licIuid
surfaces in the several cells are coplanar at that common
elevation.
During this air pumping process the electrolyte
moving through the several cells exits the battery through
the outlet port 50 in the last c:ell. If desired this
electrolyte can be collected ancl used for electrolyte
replenishment according to this invention at a later date.
At the point where air is observed exiting the outlet
port, the electrolyte in each electrolytic cell will have
a level corresponding either to the location of the inlet
end 42 of each carry-over passacle 40, or to the location
of the inlet end 54 of the outlet port 50. Accordingly,
the lengths of either the carry-over passage inlet ends or
the outlet pipe inlet end may be varied according to the
level of electrolyte desired in each cell. In a preferred
embodiment, the length of the inlet end should yield an
electrolyte level that results i.n the complete immersion
of the electrodes within each cell in order to maximize
each cell's production of electricity through its
participation in the electrochemical reaction.
_ .
CA 02177618 1999-04-06
- llB -
A consequence of the air-driven liquid level
equalizing (or adjusting) process described above is that
the head spaces in the upper encls of the cells are purged
of undesired or hazardous gases.. Such gases can be vented
to atmosphere or introduced to an air purification device
such as a scrubber or the like clS they leave the battery.
Alternatively, the air purge operation according to
methods of this invention may a]Lso be
.
CA 02l776l8 l999-04-06
- 12 -
carried out by reversing the flow of the air purge
operation as previously described and introducing air into
the outlet end 56 of the outlet port 50 and into the last
electrolytic cell 12-4. This can be achieved by selecting
a reversible pump to recirculate the electrolyte and by
reversing the direction of the pump so that air is drawn
through the electrolytic cells i-rom the outlet port 50.
In order to accommodate electro]Lyte level equilibration
using this reverse air purge operation the length of each
carry-over passage inlet and oul:let end as well as the
outlet port inlet end, shown in FIGS. 1, 5,6 and 7, would
have to be adjusted to both facilitate the hydraulic
transport of the electrolyte during the replenishment and
recirculation operations to establish the desired or
working electrolyte level in each cell during the air
purging operation. For example, in order to maximize the
electrolyte level in each of the electrolytic cells 12
illustrated in FIGS. 1, 5,6 and .7, it would be desirable to
construct battery having an outlet end 28 of the inlet
port 22, an inlet end 42 of each carry-over passage 40, an
outlet end 44 of each carry-over passage and an inlet end
54 of the outlet port extending the same distance,
preferably a short depth, into each electrolytic cell.
Configured in this manner, each electrolytic cell would be
filled completely, i.e., the electrolyte level would be
near the battery cover 18, during the electrolyte
replenishment operation. Conduc:ting the reverse air purge
operation in this embodiment would not result in a
significant degree of levelling. Rather, the air purge
operation would operate to clear. the electrolyte solution
from each of the carry-over passages 40 to eliminate any
short circuit between adjoining electrolytic cells.
Alternatively, the electrolyte ]evel could be established
at less than at m~Y;mllm level by varying the distance that
the outlet end 44 of each carry--over passage extends from
.. . .. . .....
CA 02177618 1999-04-06
- 12A -
the battery cover 18 into each electrolytic cell.
Additionally, by using the reverse air purge operation one
can obtain a different electrolyte level in the several
cells than that obt~ine~ by using the st~n~rd air purge
operation, for a set carry-over passage configuration.
The reverse air purge operation can also be carried
out in a bipolar battery configured according to FIG. 4
without changing the battery configuration. The placement
of the inlet end 42 of the carry-over passage 40, the
inlet end 54 of the outlet port 50, and the air hole 47
permits the complete filling of each electrolyte cell,
i.e., the electrolyte level wou]Ld be near the battery
cover 18, during the electrolyte replenishment operation.
Conducting the reverse air purge operation in this
embodiment, like the previously discussed embodiment,
would serve to clear any residual electrolyte from each
carry-over passage 40 to eliminate any short circuit
between adjoining electrolytic cells. In either
embodiment, the reverse air purc~e operation may be
effected by using the same pumping means used for
introducing electrolyte during l:he electrolyte circulation
operation by simply reversing i1:s operation and, thus
eliminating the need for valving in the plumbing of the
circulation system.
Collecting the electrolyte and circulating it back
through the cells of the battery in the m~nner previously
described is highly desirable when the battery is being
charged to restore capacity. During the charging
operation, a voltage is applied to the battery to induce
current flow in the battery in a direction opposite to the
direction in which current flows during discharge of the
battery. That reverse current i--low reverses the
electricity-producing electrochemical reactions and
restores the condition of active materials within the
CA 02l776l8 l999-04-06
- 12B -
battery. At the point where the active materials within
the battery are restored to a condition where their
participation in the electrochemical reactions produces a
desired discharge capacity of the battery, the battery is
said to be at 100 percent charge. Ideally,
CA 02177618 1999-04-06
the charging operation should terminate after achieving
100 percent charge. However, in order to maximize each
cell's ability to participate in the electrochemical
reactions and to store electricity, it is currently common
practice to continue the charging operation by up to 30
percent beyond 100 percent charge. "Overcharging" the
battery, as it is referred to in the trade, is an
operation used to ensure the agitation and ~iYi ng of the
electrolyte (i.e., to homogenize the electrolyte) within
each electrolytic cell after 100 percent charge has been
attained.
The homogenization of the electrolyte within each
cell as a part of a charging operation is desirable
because, as the battery is charged, the electrolyte within
the cell is restored to a specii-ic gravity indicating its
ability to participate as desired in the electrochemical
reaction productive of useful electrical energy. During
the charging operation, localized "bodies" of electrolyte
having either high or low specii.ic gravities may develop
within the electrolyte in each c:ell. Generally speaking,
the specific gravity of the elec:trolyte corresponds to the
state of charge of the electrol~rtic cell, e.g., an
electrolytic cell comprising electrolyte having a specific
gravity value of 1.3 exhibits a higher state of charge
than an electrolytic cell compri.sing electrolyte having a
specific gravity of 1Ø A batt:ery exhibits maximum
voltage capacity when each elect:rolytic cell is filled
with a volume of homogeneous electrolyte, i.e., an
electrolyte volume having a uniiorm specific gravity.
Stratification of the electrolyt:e within each cell is not
desired because it serves to recluce the voltage capacity
of the battery. Therefore, in order to maximize the
electricity producing potential of each cell, it is
CA 02177618 1999-04-06
- 13A -
desired that each cell comprise an electrolyte volume
having a uniform specific gravily. During the overcharge
operation, the current entering the battery causes
electrolysis of the water constituent of the acid
electrolyte. (Electrolysis is 1_he dissociation of water
molecules into hydrogen and oxygen gas.) Electrolysis is
intentionally produced by overcharging so that the
hydrogen and oxygen which is formed on the electrodes in
each cell will bubble up through the electrolyte volume
and cause stirring and mixing oi- the electrolyte so that
it becomes uniform throughout the cell.
Overcharging a battery is wasteful of energy and
harmful to the battery, but is c:urrently accepted as a
necessary evil and tradeoff upon performance of the
battery. Overcharging causes the battery to become hot;
if overcharge current levels are high hazardous boiling-
over of the electrolyte can occ:ur.
Heating of battery components beyond their designed
temperature parameters effectively shortens the life of
the battery. Also, during the overcharge operation, the
positive electrode in a cell unclergoes corrosion which
effectively limits, in a progressive manner the extent to
which the battery can participat:e in the electrochemical
reaction, and thus store electri.city. It is estimated
that the need to overcharge the battery to achieve
electrolyte mixing may decrease battery life by up to
fifty percent. The overcharging operation also results in
gassing due to electrolysis. The electrolysis of the
electrolyte not only produces potentially explosive gasses
such as hydrogen but operates to decrease the electrolyte
replenishment interval m~ki ng t:he need to replenish
electrolyte more frecIuent. The practice of applying more
energy to achieve overcharge ancl electrolyte m; Y; ng iS
both costly, in terms of the adcled cost associated with
CA 02177618 1999-04-06
- 13B -
the electricity needed for overcharging, and time
consuming, in terms of the extral time spent both during
the overcharge operation and during electrolyte
replenishing.
CA 02l776l8 l999-04-06
- 14 -
Accordingly the advantages associated with
eliminating the need to overcharge the battery during the
charging operation are numerous. The life of a battery
can be extended by both reducing the severe temperatures
that adversely affect the battery s active materials and
by eliminating the electrode corrosion associated with
overcharging. Eliminating eleclrode corrosion can result
in a weight savings since the battery electrodes are
largely made of lead and would no longer have to be sized
to accommodate the progressive effects of overcharge
corrosion. The generation of potentially explosive gasses
can be eliminated or greatly rec~uced and the electrolyte
replenishment interval can be extended. Additionally
eliminating the need to overcharge will result in both a
cost and a time savings associa1:ed with the overcharging
operation itself.
Although overcharging the battery during the charging
operation is not desirable charging the battery a small
amount beyond lO0 percent charge is oftentimes necessary
to overcome inefficiencies inherent in the charging
operation such as gassing which may occur before
achieving lO0 percent charge. Therefore in order to
restore the full reserve voltage capacity of a particular
battery it may be necessary to charge the battery in the
range of from lO0 to llO percent;. A preferred amount of
charging being in the range of 102 to 103 percent. This
amount of charge is far short oi. the 30 percent over lO0
percent charge that is known to be used to effect
electrolyte agitation and cause the above mentioned
undesirable side effects.
Recirculating the electrolyte through a battery in
the ~nn~r described above during the charging operation
avoids the need to overcharge. As shown in FIG. 5 as the
CA 02177618 1999-04-06
- 14A -
electrolyte is continuously introduced into the first
electrolytic cell 12-1 transported through each adjacent
cell transported out the outlelt port 50 and circulated
back into the first cell it is being uniformly
distributed within each cell and ultimately within the
battery. This circulation operation effectively
eliminates the need to overcharge because it results in
each electrolytic cell having an electrolyte volume of
uniform specific gravity and thus maximizes the
electricity producing potential of each cell. By
eliminating the need to overcha~.ge the battery the
circulation operation according to methods of this
invention makes possible all of the previously mentioned
advantages. The electrolyte circulation process may also
include routing the electrolyte from the battery through a
heat exchanger radiator or the like for purposes of
thermal management. During the charging operation the
current entering the battery causes the battery to heat.
As discussed previously heating the battery adversely
affects the active materials in the battery and thus
shortens the life of the battery. Accordingly the
ability to remove heat from the electrolyte by circulating
it through a heat exchanger or t:he like serves to keep the
battery s temperature within its design parameters during
the charging operation and thus m-Yimize the useful life
of the battery.
Additionally it is well known that the performance .
of a battery is strongly influenced by ambient
temperatures. Therefore it can be desirable to circulate
a battery s electrolyte through a heat exchanger or the
like before its operation to ensure that the temperature
of the battery is within design parameters. For example
when the ambient temperature is cold and below a battery s
CA 02177618 1999-04-06
- 14B -
design parameters, the electrol~yte can be circulated
through a heat exchanger or the like to raise the
temperature of the battery to design parameters.
Conversely, when the ambient temperatures are hot and
above design parameters, the electrolyte can be circulated
through a heat exchanger or the like
CA 02177618 1999-04-06
to lower the temperature of the battery to design
parameters.
The battery electrolyte exiting the battery may also
be stored in a reservoir or the like. During the normal
discharge and charge cycles of an electrolyte battery the
battery active material flakes away from the surface of
the electrode forming particula1e matter that settles and
collects along the bottom of eac:h cell. Particulate
matter that accumulates at the bottom of the electrolytic
cells is referred to as sediment in the trade, while
that which accumulates near the top of the cell is
referred to as moss and that which accumulates about the
sides of the cell is referred to as tree shorts . This
particulate matter is electrically conductive and thus may
accumulate to a degree within the cell to bridge
electrodes of opposite polarity thus causing a short
circuit and shorten;ng the useful life of the battery.
It is therefore, preferrecl that an electrolyte
reservoir be configured to accon~modate the physical
separation of solid particulate matter from the
electrolyte as the electrolyte i.s introduced into the
reservoir, as in the course of c:irculating electrolyte
through the battery. In a preferred arrangement the
reservoir can be a container configured in the shape of an
hourglass. The constricted port:ion of the contA;ner
should be of sufficient diameter to permit the passage of
particulate matter. The inlet t:o the reservoir may be
located above the constricted portion and the outlet from
the reservoir can also be locate!d above the constricted
portion to ensure that the particulate matter accumulating
below the constricted portion is not picked up and
circulated back through the batt:ery. Alternatively, the
particulate matter contained in the circulating
CA 02l776l8 l999-04-06
- 15A -
electrolyte may be removed outs:ide of the reservoir by
passing the electrolyte through a filter or the like.
In addition, a reservoir m2~y serve as the single
location for conveniently AC1~1; ng make up water to the
existing electrolyte and may comprise an indicator such as
a fill line or the like that a user may conveniently refer
to for determin;ng whether such make up water should be
added. The reservoir may be located to within the battery
powered device or may be locate(~ within a structure where
the battery powered device is slored. For example, the
reservoir may reside within a battery powered car at a
location that would facilitate easy access for purposes of
A~; ng water, such as locations currently occupied by
automobile w;n~ch;eld washer ancl radiator reservoirs.
The electrolyte may be introduced to the battery
during the electrolyte replenishment and circulation
procedure according to this invention by using a fluid
transport device such as a pump The pump may be
centrifugal, peristaltic or the like, and must be capable
of facilitating the fluid transport of acidic electrolyte
solutions such as sulphuric acicl. In addition, the pump
must be capable of handling the displacement of air as
well as fluid during the air-powered electrolyte levelling
and air purge procedures. The pump may be powered from
the battery itself, or from an external power supply such
as a battery charger or stAn~Arcl household voltage. The
pump should be of sufficient capacity to provide a desired
flow rate of electrolyte through the battery at a suitable
pressure. Additionally, in order to accommodate the
electrolyte level equilibration according to the
alternative reverse air purge operation, it may be
desirable that the fluid transport device be capable of
inducing a vacuum through the battery by reversing its
direction. A preferred fluid transport device is a
CA 02177618 1999-04-06
- 15B -
peristaltic pump.
During the normal battery c:harging operation, some of
the current introduced into the battery
CA 02l776l8 l999-04-06
- 16 -
to restore the battery's discha~ge capacity results in the
electrolysis of the water component of the battery
electrolyte. This electrolysis results in the production
of small amounts of hydrogen gas which may be explosive
under certain conditions. It is desirable to remove this
hydrogen gas from the battery in order to eliminate the
potential for an explosion. The hydrogen gas, or any
other gases produced during the charging operation, are
purged from the battery by the air purge procedure which
comprises transporting air through each of the electrolyte
cells of the battery as described above. By using the air
purge procedure to sweep unwanted gasses out of the
battery the unwanted gasses can be collected and disposed
of by appropriate means. In the case of hydrogen gas, the
air exiting the battery may sim~)ly be collected and vented
to the atmosphere. However, in the case of other gases
which may be hazardous or toxic, the air exiting the
battery may be routed through an air purification device
such as a filter, scrubber or the like to ~ e the
hazardous or toxic gases, routecl through a catalytic
convertor to form water, or sim~)ly routed away from the
working area and vented to the atmosphere.
FIG. 8 shows an exemplary and preferred embodiment of
an electrolyte circulation system 57 according to the
present invention. The circulat:ion system includes the
electrolyte battery, as previously concerning FIG. 1,
configured to accommodate both electrolyte replenishment
by hydraulic means and electrol~te level equilibration by
hydraulic and pneumatic means. A pump 58 of the type
previously described is positioned at a location in a
circulation loop between the inlet port 22 and the outlet
port 50 of the battery 10. The pump is powered by a pump
CA 02l776l8 l999-04-06
- 16A -
motor 59. A pump outlet 60 iS c:onnected by tubing and the
like to the inlet end of a heat exchanger 78 of the type
previously described. An outlet; end 80 of the heat
exchanger is attached by tubing and the like to the inlet
end of the inlet port 22. A pump inlet 62 iS attached to
an inlet manifold 64 comprising an air inlet valve 66 and
an electrolyte inlet valve 68. Alternatively, a single
valve may be used that is capable of switching between
electrolyte and air connections.
An inlet end of the electrolyte inlet valve 68 iS
connected through tubing and the like to an outlet 70 of
an electrolyte reservoir 72 of t:he type previously
described. The reservoir outlet: 70 iS below a minimum
reservoir electrolyte level and above the constricted
portion of the reservoir. A reservoir inlet 74 iS
positioned near the top of the reservoir and is connected
by tubing and the like to the outlet end of an electrolyte
outlet valve 82. The electrolyt:e outlet valve is
connected to an outlet manifold 84. An inlet end of the
air outlet valve 86 iS also attached to the outlet
manifold. An outlet end of the air outlet valve 86 can be
attached by tubing and the like to an air purification
device. If desired, however, the outlet end of the air
inlet valve may simply be ventecl to the atmosphere.
The outlet manifold 84 iS attached by tubing and the like
to the battery outlet port 50.
Preferably as shown in FIG. 8, there is associated
with the electrolyte reservoir 72 a water reservoir 90
which discharges to the electrol.yte reservoir via a valve
91, the operation of which is controlled by the output of
CA 02177618 1999-04-06
- 16B -
a level sensor 92. The level sensor is mounted to the
electrolyte reservoir to cause water to be added to the
electrolyte, and to restore the electrolyte volume in the
system to a desired volume, when the amount of electrolyte
in reservoir 72 becomes too sma:Ll to accommodate system
electrolyte volume loses due to evaporation and
electrolysis of the water in the electrolyte.
In a preferred embodiment, the electrolyte
replenishment and circulation procedure according
CA 02177618 1999-04-06
to this invention can be initiated by closing the air
inlet valve 66 and opening the electrolyte inlet valve 68
to permit the passage of electrolyte from the electrolyte
reservoir 72 to the inlet of the pump 58. The pump is
turned on to cause the transport of electrolyte through
the heat exchanger 78. The electrolyte enters the heat
exchanger 78 and is either cooled or heated dep~n~; ng on
whether the battery is being charged or whether the
electrolyte temperature is being adjusted to ensure
m~Y~mllm performance at the prevailing ambient temperature.
The electrolyte is circulated through the heat eYchAnger
78 and is routed through the ba1tery inlet port 22 and
into the first electrolyte cell of the battery lO. The
pump continues to introduce electrolyte into the first
cell causing the hydraulic transport of the electrolyte
through the battery, filling each cell in the manner
previously described.
After the last electrolytic cell is filled, the
electrolyte exits the battery through the battery outlet
port 50 and enters the outlet manifold 84. In the
electrolyte circulation procedure the air outlet valve 86
is closed and the electrolyte outlet valve 82 is open to
facilitate the transfer of elect;rolyte to the electrolyte
reservoir 72 where any particulate matter contained in the
entering electrolyte is allowed to settle out and pass
through the constricted portion of the reservoir to the
bottom of the reservoir where it: can not again be picked
up and circulated back through t:he battery.
The electrolyte circulation process may be conducted
throughout battery charging proc:edures to ensure that each
electrolytic cell has a homogeneous electrolyte volume of
CA 02l776l8 l999-04-06
- 172~ -
the desired temperature and uni:Eorm specific gravity
throughout each cell. If desired, the electrolyte may be
circulated for a time beyond the charging period to ensure
that the temperature of the battery is within the
predetermin~d design parameters, and to ensure the removal
of particulate matter entrained in the electrolyte.
The air pumping procedure used to equilibrate the
electrolyte levels in the sever~l battery cells according
to the present invention may be initiated by closing the
electrolyte inlet valve 68 and opening the air inlet valve
66, thus causing air to pass through the pump 58, through
the heat exchanger 7 8 and into l_he battery via the inlet
port 22. As the air is introduced into the battery the
electrolyte in each electrolytic cell will be levelled
according to previously described principles of this
invention. The electrolyte outlet valve 82 is closed and
the air outlet valve 86 is opened to permit the flow of
electrolyte and air exiting the battery to enter a
suitable liquid/gas separation clevice 88 where the air
exiting the battery can be separated and either vented or
collected and treated.
The air purging operation may be conducted after each
replenishment/circulation operat:ion to equilibrate the
electrolyte level in each electrolyte cell. The duration
of the air purge operation may c:ontinue beyond the point
where air is observed exiting the outlet port 50 of the
battery in order to sweep any hazardous gases out of the
battery where they can be properly treated.
The electrolyte circulation system described permits
the "conditioning" of the electrolyte. Electrolyte
conditioning refers to the process of ~;x; ng the
electrolyte within the battery -e;o that the battery
comprises a homogeneous electrolyte volume of uniform
CA 02177618 1999-04-06
- 17B -
specific gravity. Electrolyte conditioning also refers to
the process of adding make up w.~ter to the existing
battery electrolyte to adjust t]he specific gravity value
of the electrolyte to a predetermined range representing
optimal participation in the electrochemical reaction
producing electricity.
It is to be understood that the electrolyte
circulation system described above and illustrated in
CA 02l776l8 l999-04-06
- 18 -
FIG. 8 iS only preferred embodiment according to the
methods and principles of this invention. Other types of
circulation systems may be used to carry out the practice
of this invention. The circulation system need not
comprise all of the devices illustrated in FIG. 8, and it
need not comprise the devices in the same m~nner or order
as illustrated in FIG. 8. For ~example, a circulation
system comprising a pump, reservoir, and heat exchanger
may combine these devices in an order other than that
illustrated in FIG. 8.
Additionally, the electrolyte circulation system may
be accomplished according to principles of this invention
by, instead of pumping electrol~yte under positive
pressure, using a vacuum to dra~w the electrolyte solution
through each of the electrolytic cells within the battery
In such an embodiment, the pump 5 8 in FIG. 8 could be
positioned with its inlet 62 attached to the outlet port
50 and its outlet 60 configured to discharge into the
reservoir 72. The reservoir ou-tlet 70 could be connected
to the inlet port 22. Operating the pump would cause the
vacuum circulation of electrolyte in the reservoir
throughout each electrolytic ce:Ll. This method of vacuum
electrolyte circulation may present certain advantages
over using a positive pressure electrolyte circulation
system, due mainly to eliminating the hazards that may be
associated with an acid leak in a positive pressure acid
transport system.
Additionally, instead of using positive air pressure
to equilibrate the electrolyte levels in the several
CA 02177618 1999-04-06
- 18A -
battery cells, the levelling operation can be performed by
using a vacuum according to an alternative reverse air
purge operation. As shown in FIG. 8, the reverse air
purge operation can be initiated by reversing the
direction of the pump 58, closing the electrolyte inlet
valve 68, closing the air inlet valve 66, op~n; ng an air
outlet valve 102, closing the electrolyte outlet valve 82,
and opening the air outlet valve 86. As the air is drawn
through the battery outlet port 50 into the battery the
electrolyte in each electrolyti,: cell will be levelled
according to previously described principles of this
invention. Additionally, each carry-over passage will be
purged of electrolyte and filled with air, eliminating the
possibility of electrical short circuits between adjacent
cells. The air leaving the battery travels through the
battery inlet port 22, the heat exchanger 78, through the
pump 58, through the air outlet valve 102, and into a
suitable liquid/gas separation device 104 where the air
exiting the battery can be separated and either vented or
collected and treated.
Additionally, the electrolyte circulation system of
the present invention may be configured to circulate the
electrolyte throughout the eleclrolytic cells in a battery
in a parallel-series manner in order to accommodate a
large pressure drop associated with a battery having a
large number of electrolytic cells. For example, in a
large application calling for a battery having 250
electrolytic cells, the battery may be configured having
10 parallel circulation systems for circulating
electrolyte through 25 electrolytic cells in serial
fashion. In such an embodiment, each parallel
circulation system would have it:s own pump that would pick
up electrolyte from a common reservoir. The electrolyte
. ,
CA 02177618 1999-04-06
- 18B -
exiting the final electrolytic cell in each parallel
circulation system would be col:lected in the common
reservoir and, thus facilitate the homogenization of the
electrolyte solution throughout each of the electrolytic
cells in the battery.
The methods of replenishin/~, circulating and
adjusting the level of the battery electrolyte according
to methods of this invention ha.s been specifically
described and illustrated in the context
CA 02177618 1999-04-06
-- 19 --
of a lead-acid electrolytic battery of conventional
construction comprising four el~ectrolytic cells for
purposes of illustration and cl~rity. It is, therefore,
to be understood that the metho~s according to this
invention apply to liquid electrolyte batteries using
other electrochemical materials or comprising any number
of electrolytic cells. Also, as shown below with
reference to FIG. 4, the structural and procedural aspects
of this invention can be practiced to advantage with
liquid electrolyte bipolar batteries.
A test was conducted using a lead-acid battery
comprising three electrolytic c-311s, constructed according
to principles of this invention, to determine the
effectiveness of the circulation system in distributing
the electrolyte through the electrolyte battery during a
charging operation.
The useable voltage capacilty of the three cell
battery was completely discharged and the battery was
connected to a constant current charger. A tube was
inserted into beaker cont~i ni ng fresh electrolyte solution
having a specific gravity of approximately 1.28. The
other end of the tube was connected to the inlet of a
peristaltic pump. The outlet oiE the pump was connected to
an inlet end of an inlet port oiE the battery constructed
consistently with the foregoing description of battery 10
shown in FIGS. 1-3. Prior to commencing the charging
operation, specific gravity mea-;urements were taken in
each electrolytic cell and were measured to be
approximately 1.16. The charging and the electrolyte
replenishment and circulation operations were commenced
concurrently, and specific gravity measurements were taken
in each electrolytic cell at one hour intervals.
Measurements of the specific gravity of the electrolyte in
., . . . _ ..
CA 02177618 1999-04-06
- l9A -
the beaker (reservoir) were madle more frequently.
As shown in FIG. 9 the specific gravity in each
electrolytic cell began to rise as the electrolyte in the
beaker circulated through the t~est battery and the battery
began to charge. After approximately two hours of
charging, specific gravity measurements made in each cell
and in the beaker showed that the electrolyte specific
gravity had become uniform throughout the system. The
specific gravity of the electrolyte in each electrolytic
cell continued to rise uniformly as the charging and
circulation operations proceeded. After ten and one half
hours the voltage capacity of t:he battery was restored
(103 percent charging) and the charging and circulation
operation was completed. Restoration of full charge to
the battery was signalled when the electrolyte's specific
gravity ceased to increase and reached a predet~r~; neA
full charge specific gravity value. Also, the ampere-
hours of battery discharge before commencement of the test
was known, and full charge existed when discharge and
charge ampere-hours became equal.
In FIG. 9, curve 93 descri]bes the specific gravity of
electrolyte in the beaker, the ,-urves grouped at 94
describe the specific gravity in the several battery
cells, and curve 95 describes t]he charging energy (in
ampere-hours) applied to the battery. Line 96 denotes the
point at which the battery was restored to a condition of
full charge.
The measurement of uniform specific gravity values in
each electrolytic cell during t]he charging and circulation
operation evidenced the effectiveness of the electrolyte
circulation operation in distributing the electrolyte
throughout the battery, thus el.iminating the need to
. ~ _ , .. . .. . ..
CA 02177618 1999-04-06
- l9B -
overcharge the battery to achieve electrolyte mi Yi ng and
homogeneity.
In order to ensure charger cut off after the battery
has achieved full charge, i.e., 103 percent charge, and
prevent or guard against undesi:rable overcharge, i.e.,
greater than 110 percent charge,
.. . .
CA 02l776l8 l999-04-06
- 20 ~
a control device can be incorporated into the charging
system. FIG. 10 shows a schematic of such a charging
system comprising a battery 10, a battery charger 98, and
a charger controller 100 capable of shutting off the
charger after full charge is detected. The controller may
be of the type that measures the change in voltage as a
function of time or measures the total amount of ampere
hours charged.
A controller that measures the total ampere-hours
discharged and charged can be programmed to shut off the
charger after the charger puts into the battery the same
amount of ampere-hours removed from the battery during
discharge plus some small predet~rmined overcharge to
compensate for any losses or inefficiencies, thus
effectively protecting against overcharge.
A controller that measures the change of voltage as a
function of time can be programmed to shut off the charger
when it no longer senses a change in voltage as a function
of time. At the point of 103 p,ercent charge, the voltage
applied to the battery will no longer result in increasing
the batteries discharge potential and the battery voltage
will remain constant. Therefore, a controller programmed
to sense a lack of voltage change with time and to shut
off the charger will effectively prevent overcharge.
Alternatively, as shown in FIG.s 8 and 10, the
charger controller 100 can be configured to deactivate the
battery charger 98 dep~n~1;ng on the specific gravity value
of the electrolyte in the reser~oir 72. A specific
gravity sensor 106 can be posit:ioned within the reservoir
and electrically connected to relay specific gravity
information to the controller v.ia a lead 107. As shown in
.. _ _. . , . , . . . _ .
CA 02l776l8 l999-04-06
- 20~ -
FIG. 9, as the charging energy of the battery increases,
so does the specific gravity of the battery electrolyte.
When the battery is restored to full charge 96 the change
in specific gravity as a function of time is essentially
zero. Accordingly, the controller can be designed to
deactivate the charger a predetermined amount of time
after the specific gravity of the battery electrolyte no
longer increases as a function of time to ensure that the
battery has achieved full charge, i.e., 103 percent
charge, and prevent or guard against undesirable
overcharge, i.e., greater than 110 percent charge. The
controller 100 may also be configured to deactivate the
pump motor 59 during the electrolyte charging and
circulation operation when it senses that the specific
gravity of the battery electrolyte no longer increases as
a function of time.
The method of circulating the electrolyte according
to principles of this invention has been specifically
described as occurring concurrently with the charging
operation. However, it is to be understood that the
electrolyte circulation may be conducted at different
times during the charging operation, or may be conducted
independent from the charging operation, i.e., after the
charging operation has concluded. Tests were conducted to
determine whether the circulation operation could be
conducted at a time after the commencement of the charging
operation in order to minimize both the pump requirements
and the energy consumed by circulating the electrolyte
during the entire charging operation.
In one such test, it was discovered that initiating
the circulation operation 1/4 of the way into the charging
operation produced a homogeneous electrolyte volume
throughout the battery having a specific gravity at the
completion of the charging operation equal to that
.... . . . . _
CA 02177618 1999-04-06
- 20E~ -
realized when the circulation operation proceeded
concurrently with the charging operation. In another such
test, the electrolyte
CA 02l776l8 l999-04-06
- 21 -
circulation was initiated 3/4 of the way into the charging
operation. Like the previous test, it was discovered that
initiating the electrolyte circulation 3/4 of the way into
the charging operation produced a homogeneous electrolyte
volume throughout the battery having a specific gravity
equal to that realized when the circulation operation
proceeded concurrently with the charging operation.
Theses test results provide evidence that the circulation
operation of this invention need not be conducted during
the entire charging operation in order to provide
electrolyte homogenization; therefore, allowing a user to
~i n; m; ze the pump requirements and the energy consumed
during the circulation operation.
The construction and procedural aspects of the
battery and related electrolyte replenishing/conditioning
system according to principles of this invention have
numerous advantages which would help overcome any
perceived inconveniences or financial encumbrances
associated with replacing traditional hydrocarbon power
sources with environmentally desirable battery powered
sources in such applications as the automobile. Practice
of this invention can: (1) permit the replenishment of the
battery electrolyte to a desired electrolyte level in each
cell without the use of moving parts within the battery
and from a single convenient location; (2) increase the
electrolyte replenishment frequ~ency due to the ability to
circulate the electrolyte, eliminating the need to
overcharge the battery, and thus reducing the amount of
electrolyte lost due to water hydrolysis; (3) permit the
removal of particulate active m,aterial from the
electrolyte, eliminating the potential for electrical
short circuit within the battery; (4) increase the life of
the battery by circulating the ]battery electrolyte through
a temperature management device to maintain internal
battery temperatures within design temperature parameters
CA 02l776l8 l999-04-06
- 21~- -
both during the charging and prior to discharge of the
battery; (5) increase the life of the battery by
circulating the electrolyte during charging, eliminating
the need to overcharge the battery, and thus eliminating
corrosion which occurs at the positive electrode plate;
(6) save energy by eliminating the need to apply a voltage
to the battery in excess of that needed to achieve 100
percent charge; (7) save time by eliminating the need to
charge the battery beyond the time associated with
achieving 100 percent charge; and (8) promote safety by,
(a) permitting a user to replenish the battery electrolyte
in a m~nner that would avoiding placing the user in
contact with the acidic solution, (b) reducing the amount
of potentially explosive gaseous hydrolysis products
created during the charging process by replacing the need
to overcharge with electrolyte circulation, and (c)
removing potentially explosive gases from the battery by
air purging during the charging operation.
The foregoing description of presently preferred and
other aspects of this invention has been presented by way
of illustration and example. It does not present, nor is
it intended to present, an exhaustive catalog of all
structural and procedural forms by which the invention can
be embodied. Variations upon and alterations of the
described structures and procedures can be pursued without
departing from the fair substance and scope of the
invention consistent with the foregoing descriptions, and
the following claims which are to be read and interpreted
liberally in the context of the state of the art from
which this invention has advanced.
.
