Note: Descriptions are shown in the official language in which they were submitted.
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ROBERT P. FLICKER
SCOTT FENSTERMACHER
1 RECOMBINANT ELECTRIC STORAGE BATTERY
BACKGROUND OF THE INVENTION
Field of the Inven~ion
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This invention relates to a recombinant electric
storage battery which includes separators that retain
a selected balanced quantity of electrolyte and has
positive piates of high antimony content.
DESCRIPTION OF THE PRIOR ART
_
There has been considerable interest in
developing recombinant electric storage batteries due
to their maintenance-free capabilities, long life, and
possible manufacturing economies. Recombinant
batteries of the lead acid or nickel cadmium type
which operate by recombining the gases generated
during charging are known in the art.
Recombinant batteries usually operate on the
oxygen cycle and are designed with an excess of
negative material as compared with positive material.
During charging the positive electrodes reach full
charge an~ generate oxygen before the negative
electrodes generate hydrDgen. The batteries are
designed for optimum oxygen movement to the negatIve
~electrodes for recombinatlon with the neg~tive
~ materlal or with the generated hydrogen to form water.
By~recombining the oxygen the;internal pressure in the
battery is restrained, the cell can be sealed and the
ba$tery continuously charged.
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1 Examples of prior art batteries are found in the
following U.S. patents: Abramson No. 3,170,81~;
McClelland, et al. No. 3,704,173; McClelland, et,al~
No. 3,862,861; Peters, et al. No. 4,119,772; Habich,
et al. No. 4,320,181; Peters, et al. No. 4,373,015;
McCleltand, et al. No. 4,383,011; and Pearson No.
4,525,43~.
The use of antimony in the positive plates in a
sealed lead acid battery is described in the S~rski, et al.,
:10 U.S. Patent No. 4,401~730 ~ich issued August 30, 1983, as an
improvement where the antimony content of the positive
plates is not more than 2 percent. The Szymborski
patent also describes control ceils which contain
antimony of a 2.1 percent content, which cells are
described as showing a marked decrease in capacity
after 300 cycles,compared wi~h the cells made by
Szymborski,according to his invention,that contained
1.4 to 1.5 percent antimony.
It is known that adding antimony as a component
of the positive plates of a lead acid battery improves
performance, but it also increases the degree of
gassing of the positive plates, and no satisfactory
solution has been proposed in the prior art to
acco~nodate the higher rate of gassing.
It has been found that lead acid batteries
constructed with fibrous sheet plate separators,
having first and second fibers of different absorbency
- relative to the elect~olyte in order to control the
recombination rate, can control the degree of gassing
~30 ~ that occurs with antimony levels above 2 percent of
total alloy weight.
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1 SUMNARY OF THE INVENTION
.
This invention relates to a recombinant electric
storage battery with separators of the type that
contain a balanced amount of electrolyta, and positive
plates of the battery which contain antimony above 2
percent of total alloy weight. Control of the
recombinant rate controls the increased gassing of the
plates which provides greater current capacity.
The principal object of the inv~ntion is to
provlde a recombinant lead acid storage battery of
increased current capacity.
A Surther obJect of the invention is to provide a
battery of the character aforesaid which is economical
to construct and has a long service life.
A further object of the invention is to provide a
battery of the character aforesaid which can be
constructed in a large number of shapes and sizes.
A further object of the invention is to provide a
battery of the character aforesaid which is of reduced
weight.
Other objects and advantageous features of the
invention w;ll be apparent from the description and
claims.
It should, of course, be understood that the
description herein is illustrative merely and that
various modifications and changes can be made in the
structure disclosed without d~part~ing from the spirit
~of the invention. ~ ~
DESCRIPTION OF THE PREFERRED _MBODIMENTS
Recombinant lead~acid storage batteries in
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1 accordance with the invention include an outer sealed
I case with provisions for venting of excess internal
! gas pressure, separators, positive and negative plates
and ~lectrolyte absorbed and retained in the
separators. The separators are in close contact with
the pl~tes to wet the plates and to permit oxygen
generated by the positive plates to travel to the
negative plates for recombination with the negative
active material, or with hydrogen produced by the
negative plates. Since it is known that antimony
added to the positive plates improves cycle life and
current capacity, positive piates of a lead alloy were
constructed wi~h the following content in addition to
lead of:
~ Sb % As ~ Cu ~ Sn % S % Ca
2.30 0.20 0.08 0.23 0.01
Negative lead alloy plates were constructed with
the following content in addition to lead of:
~ Sb % As ~ Cu % Sn ~ S % Ca
<0.001 <0.001 ~O.OOOS 0.2-0.4 <0.001 0.10
The amount of electrolyte available in the
separators must be carefully balanced sin~e too much
electrolyte reduces the gas ~ransfer passageways in
~the separator, and reduces the area available for gas
recombination at the negative plate surfaces in
contact therewith. Too little electrolyte causes
raduced battery performance due to increased
resistance and insufficient sulphate ions. It is
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important to provide suff 3cient electrolyte so that
the recombinant action overcomes the increase(J gassln~
causecl by the hl~ller percentage of antimony. In
aclcJition, it is important that the separators be in
S close contact wi th the plates. This ob jective can be
obtainecl by improving the compresslon resi I lency of
the separators. Absorbent mat separators were
fabricated of first and seconcJ fibers wl-ich are inert
to a partlcular electrolyte to be used, the fibrous
sheet separators used were constructed as ~isclosed
: below.
; : The first fibers im~art to the sheet a qiven absorbency
greater thall 90 percent relative lo the particular
electrolyte, when surfactant free, wlli le the second
fibers impart to the sheet a different absorbency less
than 80 percent relative to the electrolyte, when
surfactant-free. The f i rst ancl seconcl f ibers are
present in the sheet in such pro~)ortions tllat the
sheet has an absorbency wi tl! respect to that
electrolyte, when surfactant-free, of from 75 to 95
percent. Preferably, the first fibers are glass
fibers, n~o~t desirably glass fibers having an average
diam~ter le~ss than S um. In one preferrecJ embocliment
the seconc~` fibers are organic fibers that are
25- hyclrophobic relative to the eiectrolyte, when
surfactant-free, most clesirabl~y polyethylene or
polypropylene f ibers. In another preferred embodiment
the second f ibers are coarse glass f ibers, for
example, having a diameter from 10 um to 20 um. In a
third preferred embodimenl there are both organic
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1 fibers that are hydrophobic relative to the
electrolyte, when surfactant-free, and large diameter
glass fibers, in addition to glass fibers having an
average diameter less than 5 um.
A recombinant battery was constructed using the
described badger plate and separator construction, an~
it was compared to a like recombinant battery
constructe~ with an antimony content in the positive
plates of 2.3 percent. The batteries constructed with
0 and 2.3% percent antimony content tested as shown in
Table 1.
TABLE I
Comparison of Performance and Life of a Croup 22NF Recombination
Battery with 2.3% Antimony (Sb) Positive Versus O.O% Antimony
(Sb~ Positive (PbCaSn Alloy~ -
PbCaSn* 2.3% Sb Positive **
_ Test Positive/Ne~ative PbCaSn Negative % Increase
3 Hours @ 8.7 Ampere 2.28 Hours 3.38 Hours 48%
6 Hours @ 5.28 Ampere 4.03 Hours 5.41 Hours 34%
1 Hour @ 25 Ampere 0.56 Hours 0.79 Hours 41%
20 Hour (A.H.) 25.43 A.H. 35.20 A.H. 38%
# Cycles B.C.I. 100 143 43%
Life Cycle Test (Range 125 - 16~)
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1 * PbCaSn alloy typically contains .lO~ Ca,, .25~ Sn and Pb are
remainder.
** 2.3% Sb al loy typically contains 2.2 - 2.4~ Sb, .10 - .25% Sn
and various grain refining elements.
The battery of ~he invention with 2.3 percent
antimony provided a markedly increased capacity in
contrast to the 0% antimony battery and the examples
disclosed by tlle Szymborski, et al. patent which
indicated a gratly decreased capacity with an antimony
content of greater than 2.1~.
It will thus be seen that the objects of the
invention have been achieved.
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