Note: Descriptions are shown in the official language in which they were submitted.
11 7 0 7 13 60BA-201
BACKGROUND OF l'HE INVENTION
This invention relates to small low-cost
battery chargers offering superior charging performance
for consumer-size rechargeable batteries and more
versatility over known chargers.
The present invention is an improvement over
existing battery charging systems of the type described in
U.S. Patent No. 4,009,429 dated February 22, 1977, F.H.
Mullersman. Such a charging system is marketed by General
Electric Company, and enables cells of several different
siæes to be charged. It comprises a battery charger
unit which can be plugged into an electrical receptacle
and one of several mating cell-holding modules which holds
and interconnects two or four rechargeable cells.
r~he foregoing battery-charginy system has
achieved wide commercial accep~ance with the public.
It is effective, relatively inexpensive and easy to
use. The terminals on the battery charger unit, and
the construction of the cell-holding modules are such
that it is virtually imposslble to incorrectly mate
the cell holding module with the battery charger. An
.
important feature of that charger is the fact that it
can be plugged directly into an electrical receptacle
so~that the charger, when mated with the cell-holding
module, forms an integral unit that is supported by
the receptacle ltself. This eliminates the need for
electric extenslon cords and the like, and enables
the consumer to leave the charger plugged into the
receptacle during cell charging. Moreover, the
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charger current is such that the cells may be left on
30 "on-charge" continuously. ~
A limlting~feature of;the exlsting battery
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117Q713 60BA-201
charger just described, however, is the fact that it
can accept only one type of cell-holding module at
any given time. Thus, should it be desired to charge
immediately a pair of needed C-size cells while AA-size
cells, for example, are being charged, the AA cell-
holding module must be removed from the charger
before charging is complete in order to substitute
the C-si~e cell module. Another limitation of the
existing charger is the fact that its charging current
is restricted to about .lC, where C is the capacity of
the cell in ampere-hours (~h). Thus, for a typical
AA-size battery having a nominal open circuit voltage
of 1.2 volts and a capacity of .5 Ah, the C/10 charg~
current rate is S0 mA. At this rate, the recommended
charging time is 12-16 hours. It is desirable to
increase the charging rate up to about C/6 or .15C
in order to enable the cells to attain full charge
in 8-12 hours.
In order to achieve a higher charge rate,
however, a larger transformer is required. This, in
general, requires that the battery charging unit be
able to withstand the qreater mechanical loads
transmitted to the hlade connectors which plug into
the outlet receptacle.
The present invention carries forward the
teachlngs and advantages of the battery chargers and
charging systems described in the above-mentioned
U.S. Patent No. 4,009,~429. The present battery
charger is adapted to mate with existing cell-holding
modules but,~in addition, supplied a greater charging
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current and is configured to~accept two cell-holding
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60BA-201
117V713 ` .
modules simultaneously, whether the cells to be
charged are the same or different si~es. Thus, in
the present invention, it is possible to charge
simultaneously cells of the AA, C and D size, as
well as 9-volt application batteries. Additionally,
the battery charger is arranged so that, when cell-
holding modules are mated with it, the system does
not block the second receptacle of a duplex outlet.
SUMMARY OF THE INVENTION
- The present invention achieves the foregoing
and other advantages through a novel cooperation of
its essential elements. The battery charger comprises
a charger housing having two opposed, generally
parallel sides for the mounting of separate battery
modules to be charged, these sides having affixed
thereto first and second sets of external terminals
of the battery module, the terminals being adapted to
releasably support the module. A transformer at the
interior of the housing has a core member, a primary
winding and two secondary windings wound on the core,
the secondary windings being connected respectively
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to the external terminals on the opposed sides so as
to provide charglng current thereto. A pair of blade
connectors is electrically connected internally to the
primary winding and extend from that side of the
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housing which is intermediate the opposed sides,
these connectors being spaced apart in the direction
of spacing between the opposed~sides and supporting
~30 the charger iD the~electrical receptacle. ~In the
preferred embodiment, a grounding~pin is used to
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I 170713 60BA-201
assist in supporting the load of the battery charger.
This grounding pin is mechanically affixed to the core
structure of ~he transformer and extends through the
housing for acceptance by the ground contact of the
receptacle.
DESCRIPTION OF THE DRAWINGS
For a complete understanding of the invention,
reference should be made to the following detailed
description and to the drawings, in which;
FIG. 1 is a pictorial representation of a
battery charger in accordance with the invention;
illustrated with two types of cell-holding modules
that may be used therewith;
FIG. 2 is a side ele~ation view of the battery
charger;
FIG. 3 is a plan view of the charger;
FIG. 4 is a cross-sectional view taken along
the line 4-4 of FIG. 3;
FIG. 5 is an exploded ~iew of the componPnts
of the charger;
FIG. 6 is a partial view in cross-section
taken along the line 6-6 in FIG. S; and
FIG. 7 is a series of electrical diagrams
of the battery charger and representative cell-holding
modules that may be coupled to it.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. l, the battery charger of the invention
is seen to include a housing member 10, a pair of~blade
: connectors 12, 13 and a ground pin 14, all of which are
l~70713 60BA-201
recei~ed by the respective contacts of an electrical
outlet receptacle (not illustrated) when the charger
is plugged into the outlet for operation. These three
connectors 12-14 serve not only to couple electrical
power to the charger, but also to support p~ysically
the charger and the modules which are mated thereto.
Housing member 10 has a pair of opposed,
generally parallel sides 16, 18 in which are formed
recessed surfaces 17 and 19. Sides 16, 18 and blades
12, 13 are spaced apart along the same direction such
that, when the charger is mated with two cell holding
modules and plugged into a receptacle, it will not
block the second outlet of a ~uplex outlet ~ixture.
The connector blades 12, 13 and grounding pin 14
extend from inside the case through the housing cover
member 20 which closes the open side of housing member 10.
In FIG. 1, two dif~erent types of representative
cell-holding modules are shown. On the left side of
the charger is a module 22 having a capacity for four
AA-size cells 23. On the right of the charger, shown
removed, is a 9-volt size battery 24 mated to an adapter
25. The cell-holding module 22 is described in detail
in the above-mentioned U.S. Patent No. 4,009,429, and
also in U.S. Patent No. 4,173,733, dated November 6, 1979, of
General Electric Company. The battery charging module
22, holding four AA-size batteries, is a three terminal
holder mating with one of the sets of terminals at the
side of the charger. The adapter/holder 25, on the
other hand, is a two-terminal de~ice adapted to mate
with two of the three external terminals at either side
of the charger. The external charging terminals are
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clearly visible in the drawings and are similar to the
terminals at the top of the prior commercial charger
described above. In this case, however, there are
two separate sets o~ three external terminals, and
they are located at opposite sides of the charger;
one set, 26, 27 and 28 on recessed surface 17, and
another set, 30, 31 and 32 on recessed surface 19.
Terminals 26-28, 30-32, are snap-type terminals which
releasably support the weight of the modules when the
modules are snap-fastened onto the charger It will
be noted that the external terminals at the sides of
the charger are asymmetrically situated with respect
to the recessed surfaces 17, 19, so as to preclude
inadvertent misconnection of a cell-holding module
or adapter. The walls 17a, l9a, formed in the side
of the housing by the recessing of the surfaces
cooperate in the terminal locating function of the
charger, in that the wall prevents a module from
being turned around and connected with reversed
polarity. Additionally, there is a small T-shaped
projection 35 disposed between the terminals at each
side of the battery charger. Its function is to
assist in the orienting and disconnecting of the
terminals of the module relative to the charger.
Referring to FIGS. 4-5, the interior of
housing 10 carries a charging transformer 40 comprising
a core assembly 41, a primary winding 43 wound on the
core, and two secondary windings 45, 46 also wound on
the core. The transformer steps down the applied
line voltage, the secondary windings supplying ac
charging current at low voltage (e.g., 10 volts rms)~
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~1707 13 60BA-201
As is conventional, the primary and secondary windings
of the transformer are wound about a bobbin structure
47 which subsequently is inserted over the center leg
of the core 41 before the back section 41a of the
core is added to complete the magnetic circuit. In
accordance with the invention, the transformer windings
are selected to provide a nominal charging current of
approximately .15C to the external terminals. Also
in accordance with the invention, the transformer is
connected to these external terminals such that the
corresponding external terminals on the respective
sides are oppositely poled electrically, the purpose
of which will be explained shortly. The transformer
core structure supports the blades 12, 13, which are
mounted in insulating blocks 48, 49 comprisin~ part of
the bobbin 47.
Encasing the core laminations 50 ~separately
illustrated) and forming an integral part of the core
is a metal channel 51 which clamps together the
laminations. This structure is shown in detail in FIG.
6, which is a view in partial cross-section along the
line 6-6 in FIG~ 5. As shown, channel member 51 also
serves as a mounting plate for the grounding pin 14,
To that end, it has a slightly raised section 51a in
the vicinity where the pin 14 is joined to it.
A special feature of the invention is the
ability of the charger to accommodate either one or
two externally connected modules without any ancillary
mechanical support. ~ince the transformer assembly
and the housing containing the external terminals
form a unitary mechanical structure, any forces
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applied to the housiny are also transmitted to the
transformer assembly. It will be seen, therefore,
that torque and gravitational forces resulting from
the affixing of an external module to one or both sets
of external terminals are transmitted by the housing 10
to the transformer assembly and, consequently, to the
blade connectors 12, 13 and grounding pin 14. In
order to reduce the torque that would be applied to the
connectors by connecting a single module or modules of
different weight to the charger, thereby creating a
mechanical imbal.ance, the casing, transformer wi.ndings
and core all are made narrower in the dimension between
the two module~receiving faces. Thus, the cross-sect:ion
o~ the transformer core 41 is narrower in the direction
of spacing between the two moclule-receiving faces than
it is in the direction of spacing between the other
two sides of the housing. In one preferred embodiment,
the core cross-section is 1/4 inch x 3/8 inch. Also,
grounding pin 14 aids in resisting torque forces
because it is mechanically and rigidly secured to the
metal channel 51 of the transformer core.
Referring to FIGS. 4 and 5, ~he transformer
terminals T1 - T6 are affixed to the core bobbin
assembly for connection by wire leads 55 to appropriate
ones of the terminals 26-28, 30-32. In practice,
these leads 55 are first affixed to the internal part
of the external terminals and subsequently are soldered
to the transformer terminals Tl - T6 prior to placement
of the transformer assembly into the case 10.
Thereafter, cover 20, which has cut-outs for receiving
the blade connectors 12, 13 and grounding pin 14, is
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put into place to close the housing 10. Cover 20 is
secured to the housing member 10 by any appropriate
bonding method, for example, sonic welding.
FIG. 7 illustrates the electrical circuits
that may be associated with the charger, which is
shown on the left-hand side of the figure. As
previously noted, the primary winding 43 is wired to
terminal connectors 12, 13 for connection to line
voltage E LINE' Secondaries 45, 46 have their
respective terminals Tl - T3 and T4 - T5 wired to
external terminals 26 - 28 and 30 - 32l respectively,
also as previously explained. The three figures to
the right of the trans~ormer schematically illustrate
three types of loads, LOAD A, LOAD B AND LOAD C,
which may be encountered by the charger during use.
- LOAD A represents the electrical schematic
for battery-charging modules 22 of the type illuskrated
in FIG. 1, each holding two or four cells. With two
such modules connected to the charger, up to eight
AA-size cells can be charged at one time. These modu]es
contain internal circuits for interconnecting the cells,
and for rectifying the applied current. Rectification
is brought about by the diodes 60, 61 connected in
series with the cells. These diodes also preclude
inadvertent discharge of the cells in the event of
accidental shorting of any of the terminals Al - A3,
of A4 - A6. It will be appreciated that upon connection
of the battery charger primary to an external source
E LINE~ and assuming that two four-cell modules 22
are attached to the charger, charging current ICH
will flow simultaneously through the cells connected
~ 1707 l 3 60BA-201
between terminals Al and A2, and through the two cells
connected between terminals A5 and A6 of the second
module. This is because the transformer secondaries
are poled so that the corresponding external terminals
are electrically out of phase. When the charger is
connected to loads such as LOAD A, this opposite
electrical polarity has no material significance, since
each secondary will distribute no more than one-half the
maximum total charging current during any half cycle
irrespective of the number of cells held by the
modules 22. Specifically, because the diodes 60, 61
are connected so as to be alternately conducting, no
more than four cells are supplied with charging current
during any half-c~cle of line current.
hOAD B represents the type of load encountered
by the charger when two C-size or two D-size cells 64
are connected to the charger in a two-cell module 63,
which includes rectifying diode 64. Hexe the charger
is sensitive to the flow of charging current. If
the secondaries of the charger were improperly poled
electrically, it would be possible for the charger to
deliver the maximum total charging current during only
one-half cycle of the input wave form, with no charging
current being delivered during the other half of the
waveform. This condition would subject the charger
to very poor voltage and current regulation and, to
a certain extent, would require the transformer to be
designed to handle more primary current than necessary.
For this reason, the corresponding external terminals
of the charger 26, 30 are poled so as to be electrically
out of phase while terminals 26 and 32 are in phase.
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Thus when terminal 26 is at maximum positive amplitude,
terminal 32 is also at maximum positive amplitude and
terminals 28 and 30 are at maximum negative amplitude.
And when loads of the LOAD B type are connected, current
is delivered to the respective modules on separate
half-cycles of the input wave. The same situation prevails
when charging loads such as LOAD C. This is the type of
load encountered with adapter/battery combinations, such
as illustrated in FIG. 1 by battery 24 and adapter 25.
Here again, the adapter includes the diode 66, as well
as a current limiting resistor 67 in order to protect
the generally smaller size cells making up the battery
from receiving excessive charging current. Various
embodiments o~ the adapter and battery will be found in
U.S. Patent Nos. 4,211,968, July 8, 1980; 4,213,079,
July 15, 1980; 4,229~686, October 21, 1980; and in
Canadian application Serial No. 327,414 filed May 11, 1979;
all assigned to the same assignee as the present invention.
The table below sets forth the charging current
delivered at the minimum and maximum values of applied
line voltage ~or the various types of loads shown, assuming
that the two modules are connected to the transformer.
LOAD A (2, 4, 6 or 8 Cells each rated at 500 mAh)
ELINE EB ICH
(AC Volts) (DC Volts) (mA)
104 2.9 50 Min.
127 2.3 100 Max.
LOAD B (2 or 4 Cells each rated at 1.0 Ah)
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ELINE EB ICH
(AC Volts) (DC Volts) (mA)
104 2.9 110 Min.
127 2.9 160 Max.
~170713 60BA-201
LOAD C (1 or 2 Batteries each rated at 65 mAh)
ELINE EB ICH
(AC Volts) (DC ~olts) (mA)
102 8.7 8 Min.
127 817 18 Max.
It is seen that AA-size cells (~OAD A) rated
at 500 mAh are charged nominally at a rate of .15C
(75 mA) at ELINE = 115 volts. Typical C size cells
rated at 1.0 Ah will be charged at a rate of about .14C
(140 mA) when line voltage is 115 volts. Batteries
(LOAD C) rated at 65 mAh are charged at a .2C rate
when line voltage is 115 volts. Battery charging
current in this instance is limited by the 56 ohm
resistor in the charging circuit of adapter 25, and
could be increased by reducing the resistance value.
Current draw is dependent upon the cell emf and its
polarization voltage toge-ther with the transformer
characteristics. However, charging current obtained
in the present invention is significantly higher than
that furnished in the prior single-module charger.
Phasing of the transformer secondary winding
so that the corresponding external terminals are
oppositely phased brings about operation at higher
charging currents than would be obtained with in-phase
secondaries. By way of comparison, for one case of
LOAD B, a charger with in-phase secondaries produced
charging currents averaging from 95 mA to 117 mA.
Out-of-phase secondaries produced charging currents
averaging from 112 mA to 146 mA, or 15% - 25% higher.
While the use of two secondary windings is
preferred, owing to the better current regulation
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117V7 13 60BA-201
obtained when changing from the two cell to four cell
configurations of load A, it is possible to employ a
single non-tapped secondary winding when poorer charge
current regulation can be tolerated. In such case, the
end terminals of the secondary winding are connected
to the corresponding external terminals at both sides
of the charger, instead of only one side. If this is
done, it is preferable to employ rectifying diodes
between the secondary winding and the external terminals
so that char~ing current pulses supplied to the
respective sets of terminals occur on alternate lobes
o~ the sine wave. This improves the current regulation
by insuring that a charging load connected to one set
of terminals does not conduct current at the same
instant as a load connected to the other set of terminals.
In other modifications, the charger may
incorporate rectifying diodes internally of the housing
as, for example, in cases where the cell-holding module
does not have any rectifying means. The diodes would
be connected between one of the transformer termlnals
Tl, T3 or T4, T6 and the corresponding external
terminal. It should also be noted that the rectifier
could be connected so as to be compatible with certain
cell-holding modules of the type illustrated in which
diodes are incorporated therein.
From the foregoing, it will be seen that
the improved charger of the present invention provides
versatility in several features not found in the
prior art chargers. Specifically, lt permits~the
simultaneous connection and charging of more than
one external battery circuit or module, and permits
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1~707 13 60BA-201
the mixing of several types and kinds of loads which
may require different charging currents. The charger
is inexpensive, compact, attractive, and allows use
in a duplex receptacle while leaving the second
receptable accessible for use by the consumer. In
addition to the foregoing, it permits cells to be
charged at significantly faster rates. This follows
from the ability to package a larger transformer
within a compact case while meeting the safety
requirements of restricted mechanical stresses applied
to the receptacle connectors.
Although the invention has been described
with reference to the preferred embodiment, it will
be understood that certain minor modifications and
variations can be made within the scope and spirit
of the invention. Accordingly, except as expressly
limited by the appended claims, the invention should
not be considered restricted to the embodiment
illustrated.
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