U.S. patent application number 10/028464 was filed with the patent office on 2003-06-26 for parallel battery charging device.
Invention is credited to Trepka, Ron.
Application Number | 20030117109 10/028464 |
Document ID | / |
Family ID | 21843588 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030117109 |
Kind Code |
A1 |
Trepka, Ron |
June 26, 2003 |
PARALLEL BATTERY CHARGING DEVICE
Abstract
A battery charging device for simultaneously charging the cells
of a multi-cell battery in parallel wherein an induction coil
distributes and isolates the charging energy to each cell. The
parallel battery charger may be used with any battery having common
two-electrode cells without breaking the inter-cell connections.
Additionally, each cell may include a third or charging electrode
that is used exclusively for charging. Each cell of this type of
battery is charged by coupling a third electrode and a bifunctional
electrode in parallel with the battery charger.
Inventors: |
Trepka, Ron; (Cleveland,
OH) |
Correspondence
Address: |
John J. Del Col
Renner, Otto, Boisselle & Sklar, LLP
Nineteenth Floor
1621 Euclid Avenue
Cleveland
OH
44115-2191
US
|
Family ID: |
21843588 |
Appl. No.: |
10/028464 |
Filed: |
December 21, 2001 |
Current U.S.
Class: |
320/126 |
Current CPC
Class: |
H01M 10/46 20130101;
H01M 12/08 20130101; H02J 7/0018 20130101; Y02E 60/128 20130101;
H02J 7/0024 20130101; Y02E 60/10 20130101 |
Class at
Publication: |
320/126 |
International
Class: |
H02J 007/00 |
Claims
What is claimed is:
1. A battery charging system comprising: a parallel battery
charging device comprising: an induction core; an input coil
magnetically coupled to the induction core; and a plurality of
output coils magnetically coupled to the induction core; a
plurality of regulators in communication with the plurality of
output coils; and a plurality of cables extending in parallel
between the plurality of regulators and a number of battery
cells.
2. The battery charging system of claim 1 further comprising a high
frequency source.
3. The battery charging system of claim 1 further comprising a
charge controller.
4. The battery charging system of claim 3 wherein the charge
controller includes a current sensor.
5. The battery charging system of claim 3 wherein the charge
controller includes a top-off timer.
6. The battery charging system of claim 1 further comprising a
power source.
7. The battery charging system of claim 6 further comprising a high
frequency source and wherein the power source includes a high power
factor corrector.
8. The battery charging system of claim 2 further comprising a
braking energy recovery device.
9. The battery charging system of claim 1 further comprising a
tri-electrode multi-cell battery.
10. The battery charging system of claim 7 further comprising a
charge controller having a current sensor.
11. The battery charging system of claim 10 wherein the charge
controller includes a top-off timer.
12. A parallel battery charging system comprising: a power source;
a high frequency source; a charge controller; a transformer; and a
plurality of charging circuits coupling the transformer to a
plurality of battery cells in parallel.
13. The battery charging system of claim 12 further including
voltage and current sensors in each charging circuit.
14. The battery charging system of claim 12 wherein the plurality
of charging circuits include a plurality of regulators and a
plurality of cables for connection to the plurality of battery
cells.
15. The battery charging system of claim 12 wherein the transformer
includes an input coil, an induction core, and a plurality of
output coils.
16. The battery charging system of claim 13 wherein the charge
controller regulates a DC supply source using the voltage and
current values from each charging circuit.
17. The battery charging system of claim 12 wherein the power
source includes a high power factor corrector and an DC to DC
converter; wherein the charge controller includes a current sensor
and a top-off timer; wherein the transformer includes an input
coil, an induction core, and a plurality of output coils; and
wherein the plurality of charging circuits include a plurality of
regulators and a plurality of cables for connection to the
plurality of battery cells.
18. A rechargeble power system for an electric vehicle comprising:
a high frequency source; a transformer; a tri-electrode multi-cell
battery; a plurality of charging circuits in parallel connection
between the transformer and a plurality of cells of the
tri-electrode multi-cell battery; and a braking energy recovery
device.
19. The rechargeble power system of claim 18 further comprising a
charge controller that uses current and voltage feedback from each
charging circuit to regulate the power to the transformer.
20. The rechargeble power system of claim 19 wherein the
transformer includes: an input coil, an induction core, and a
plurality of output coils coupled to the plurality of charging
circuits.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a device and
method for charging electrochemical cells of a multi-cell battery
or the simultaneous charging of multiple batteries. In particular,
the invention relates to charging a battery with multiple cells
wherein each cell includes a third or charging electrode that is
used exclusively for charging. Each cell of the battery is charged
simultaneously by coupling a third electrode and a bifunctional
electrode in parallel with the battery charger. An induction coil
distributes and isolates the charging energy to each cell. The
cells of the battery, typically wired in series, require no
disassembly for charging. The battery charger is be used with a
metal-air battery to prolong the life of the cathode but may also
be used to charge common two-electrode multi-cell batteries in
parallel without breaking the inter-cell connections. It may also
be used to charge a plurality of conventional two-terminal
batteries wired in parallel.
BACKGROUND OF THE INVENTION
[0002] Generally, battery packs include several battery cells
connected in series. Ideally, each of the battery cells within a
battery pack will have similar charging, discharging, and
efficiency characteristics. However, this ideal scenario is not
normally encountered. Thus, a battery pack ordinarily contains
several multiple battery cells with each battery cell having
different charging characteristics. This condition may produce many
problems related to the overcharging and undercharging of the
battery cells. For instance, fully charging one battery cell in a
battery pack and continuing to charge it may result in overcharging
and damage to the fully charged cell. Likewise, ending a charge
cycle when only one battery cell is fully charged may result in
undercharging one or more of the other battery cells in the battery
pack. Therefore, there is a need for a system to provide an
isolated charging cycle that accommodates multiple battery cells
having varying charging characteristics.
[0003] The present invention relates generally to a method and
apparatus for rapidly and safely charging a plurality of battery
cells from a single power supply. Given the anticipated
proliferation of electric vehicles including electric scooters, it
will be necessary to have a reasonably standardized recharging
apparatus located at, for instance, the vehicle operator's
residence, place of business, parking garage, recharge station, and
the like. Additionally, the same design may be used to
simultaneously charge multiple batteries for portable devices such
as personal computers, cellular phones, and the like.
[0004] Generally, there are two types of battery cells. Cells that
are useful for only a single discharge cycle are called primary
cells, and cells that are rechargeable and useful for multiple
discharge cycles are called secondary cells. There are many
varieties of secondary cells including the common lead-acid and
nickel-cadmium (ni-cad) batteries and the less common metal-air
batteries such as the zinc-air battery disclosed in patent
application Ser. No. 09/552,870, herein incorporated by
reference.
[0005] Battery packs comprised of metal-air cells provide a
relatively light-weight power supply. Metal-air cells utilize
oxygen from ambient air as a reactant in an electrochemical
reaction. Metal-air cells include an air permeable electrode as the
cathode and a metallic anode surrounded by an aqueous electrolyte
and function through the reduction of oxygen from the ambient air
which reacts with the metal to generate an electric current. For
example, in a zinc-air cell, the anode contains zinc, and during
operation, oxygen from the ambient air along with water and
electrons present in the cell are converted at the cathode to
hydroxyl ions. Conversely, at the anode zinc atoms and hydroxyl
ions are converted to zinc oxide and water, which releases the
electrons used at the cathode portion of the cell. Thus, the
cathode and anode act in concert to generate electrical energy.
[0006] Metal-air batteries may be charged mechanically and
electrically. Mechanical charging is accomplished by physically
replacing the electrolyte, the electrodes, or a combination
thereof. (For example, see U.S. Pat. Nos. 5,569,555; 5,418,080;
5,360,680; and 5,554,918). Such a charging method requires special
equipment, special skills, an inventory of electrolyte and
electrodes, and a plan for storing and disposing of hazardous
chemicals. Conversely, electrical recharging avoids these
disadvantages. The electrically rechargeable metal-air cell is
recharged by applying a charging voltage between the anode and
cathode of the cell and reversing the electrochemical reaction.
During recharging, the cell discharges oxygen to the atmosphere
through a vent.
[0007] While clean and efficient, electrical charging of a
conventional multi-cell battery does have some other disadvantages.
In particular, most multi-cell batteries are designed such that the
cells are connected in "series" such that the discharge voltage
between the battery terminals may be increased. For example, a
12-volt battery is normally comprised of 6 battery cells, each
producing 2 volts, wired end-to-end in "series" to provide 12 volts
across the two battery terminals. Such a configuration may be
electrically recharged by applying a charging voltage across the
two battery terminals to reverse the electrochemical process that
occurs on discharge. When connected for charging in this fashion,
each battery cell wired in series, necessarily receives the
identical current flow regardless of its current state of charge
and ability to convert this energy to electrochemical storage.
[0008] By forcing the same charging current to each cell, charging
the battery cells in series is disadvantageous. During the
electrochemical recharge cycle of a battery cell, the cell passes
through several stages of charging. It is well known that during
charging, a phenomenon known as "gassing" occurs, that is to say,
the battery electrolyte dissociates into gaseous components which
may emanate as bubbles. It is usually desirable to reduce the
battery charging current during "gassing" so as to avoid damage to
the electrode which would otherwise be caused by maintaining the
charging current at the higher levels permissible in the
"pre-gassing" or "bulk-charge" phase of charging. Thus, it is
desired that the battery charger provide a separate charging
circuit to each battery cell such that the charging current may by
optimized for each stage of a cell's charging cycle.
[0009] It remains that the two-electrode cells of conventional
batteries, connected in "series," cannot be charged
"conventionally" through separate charging circuits as the cells
are linked end-to-end. Such batteries may charged in parallel by a
conventional battery charger only if the inter-cell connections or
links are broken or disconnected. In this manner, each cell is
independent and separate charging circuits may be attached to each
cell.
[0010] In the metal-air battery arena, there are two main types of
electrically rechargeable batteries. One type includes those with
three electrodes for each cell, namely, a bifunctional anode, a
discharge cathode, and a charging-electrode (i.e. a third
electrode). The discharge cathode is designed to optimize the
discharge cycle of the metal-air cell and may be incapable of
recharging the cell. Instead, the charging-electrode is used to
recharge the metal-air cell. Another type of metal-air cell
includes two electrodes, both electrodes being bifunctional. The
bifunctional electrodes function in both the discharge mode and the
charge mode of the cell, thus eliminating the need for a third
electrode. Bifunctional electrodes, however, suffer from a major
drawback; they do not last long because the charging cycle
deteriorates the discharge system (i.e., bifunctional electrodes
suffer from decreasing performance as the number of
discharge/charge cycles increase). In some cases as the voltage
creeps up the cell may develop a short circuit as a result of a
zinc dendrite forming a metallic bridge to the positive electrode,
and will consequently cease to function even though the cathode is
in good condition and capable of further service.
[0011] Thus, tri-electrode cells are advantageous when compared to
two-electrode cells in that they offer more stable performance over
a greater number of discharge/recharge cycles. In view of the above
and the increased availability of tri-electrode batteries, there is
a need in the art for an improved battery charging device and
method for charging each of the battery cells independently and
simultaneously.
[0012] The need for an improved battery charging device with cell
balancing is illustrated by the following scenario. For example, a
battery with four cells intended to be identical typically are not
identical for many reasons. In a metal-air cell, the electrolyte
may not wet the entire anode thereby leaving useable material
isolated. Through cycling, the zinc can become detached from the
current collector and become isolated. The resulting parasitic loss
may not be equal and some cells will self discharge differently.
During discharge, one or more cells will determine the end of
discharge. The remaining cells will have some residual energy but
cannot be discharged in series as that would damage the empty
cell(s). On the next charge cycle, the cell with the most residual
charge will be fully charged prior to the other cells, if the cells
are charged in series. Further series charging may damage the fully
charged cell and the remaining cells are denied a full charge. As
the process continues, the cells unbalance further and each cycle
capacity is reduced. FIG. 3A shows a set of nickle cadmium cells
that are unbalanced by 10 ampere-hours. In this case, 3
ampere-hours is restored to the unbalance after charging.
SUMMARY OF THE INVENTION
[0013] This invention relates to a parallel charging system for a
multi-cell battery wherein each battery cell may or may not include
a third charging electrode. The charging electrode eliminates the
need to disconnect cells for parallel charging. The parallel
charging system disclosed herein can provide the same function. The
invention allows for cell charging via the respective charging
electrodes without breaking inter-cell connections. Further, the
invention provides for isolation of each charging circuit and
battery cell by employing an induction core operatively coupled to
each cell. Each cell may be connected to the induction core such
that the charging current is provided to each cell independent of
the other cells via a separate circuit. The induction core
automatically balances the current to each cell based on the cell's
ability to draw current. More current is provided to the cells with
a lower charge level and voltage.
[0014] In the simplest form, cell balancing is achieved using
transformer theory. A load on a secondary winding is reflected to
the primary winding by the transformer's turn ratio. Each secondary
winding reflects it's load and if the transformer is tightly
coupled, each secondary winding appears as if it were connected in
parallel. Each secondary winding draws power as if it was connected
to a single supply. This configuration does not require a regulator
but just a diode set and a shunt for current measurement. This
simple configuration is useful and cost effective as it requires no
extra components and performs the required cell balance.
[0015] For example, as shown in FIG. 1, the invention allows for
parallel charging of a multi-cell battery wherein the battery cells
incorporate a separate or third charging electrode in addition to
conventional positive and negative discharge electrodes.
[0016] The present invention affords for such charging through a
charging electrode without the breaking of inter-cell connections.
This is accomplished by providing the charging energy through an
induction coil so as to provide electrical isolation of each cell.
In addition, the present invention may be employed to charge
several two-terminal batteries simultaneously regardless of whether
they are multi-cell batteries or single cell batteries.
[0017] The present invention may also be employed to parallel
charge the cells of a conventional two-electrode cell battery
without requiring disconnection of the battery cells. As described
herein, the isolation of the secondary windings of the transformer
allows the parallel battery charger disclosed to be used where a
conventional parallel charger would fail.
[0018] The present invention also provides a battery charger for
charging through a third electrode (i.e. a charging-electrode) used
in metal-air cell batteries. Such third electrodes may be formed
from a mixture of an lanthanum nickel compound and at least one
metal oxide, and support structure. The present invention provides
a charging system and method for metal-air cells that provides
stable performance over a large number of charge/discharge cycles.
The result is improved metal-air battery performance and improved
battery life.
[0019] Additionally, when employed in vehicular applications, a
braking energy recovery device may be included in the charging
system to allow for conversion of kinetic energy back into
electrochemical storage in a electrochemical/mechanical system.
[0020] In one embodiment, the present invention relates to a
battery charging system that isolates the parallel charging of each
individual cell using an induction coil.
[0021] In another embodiment, the present invention relates to a
battery charging system that balances the parallel charging of each
individual cell using an induction coil and incorporates a current
sensor to determine the end charge of each cell and further may
include a top-off timer.
[0022] In another embodiment, the present invention relates to a
battery charger that allows balanced parallel charging to each cell
of a conventional multi-cell battery with two-electrode cells
without breaking the intercell connections.
[0023] In another embodiment, the present invention relates to a
battery charging system that balances the parallel charging of each
individual cell using an induction coil and recaptures the braking
energy for use in battery charging.
[0024] In another embodiment, the present invention relates to the
parallel battery charging system for simultaneously charging
several conventional two terminal batteries in parallel.
[0025] In another embodiment, the present invention relates to a
parallel battery charging system wherein current and voltage
sensors are applied to each charging circuit and are used to
control the charging cycle.
[0026] In another embodiment, the present invention relates to a
method of charging any battery by parallel charging of each
individual cell using an induction coil.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a schematic view of the structure of a parallel
battery charger and an associated tri-electrode multicell battery
in accordance with the present invention;
[0028] FIG. 2 is a schematic view of the structure of a parallel
battery charger and an associated two-electrode multi-cell battery
in accordance with the present invention;
[0029] FIGS. 3A and 3B are typical graphs representing the charge
and discharge performance of battery cells as detailed in the
specification;
[0030] FIG. 4 is a schematic view of the structure of a parallel
battery charger used to charge conventional two-terminal batteries
simultaneously in accordance with the present invention; and
[0031] FIG. 5 is a schematic view of the structure of another
embodiment of the parallel battery charger where the current and
voltage is sensed at each cell in accordance with the present
invention.
DETAILED DESCRIPTION
[0032] The present invention involves a system and method for
charging multi-cell batteries using a parallel battery charger
individually connected to each cell of a multi-cell battery. Such
batteries may include metal-air batteries or any conventional
multi-cell batteries without disconnecting the conductors that link
the cells in series. Additionally, the parallel charging system may
be used wherever several conventional batteries are to be charged
and the isolation provided to each charging circuit by the
induction loop is beneficial.
[0033] Referring initially to FIG. 1, FIG. 1 shows a diagramatic
view of the structure of a parallel battery charging device 20 and
an associated tri-electrode multi-cell battery 30 in accordance
with the present invention. The first portion of the circuit, which
is independent of the battery charging circuit, is a power source
10. The power source 10 includes an electrical energy supply such
as an alternating current power buss 12. The source of alternating
current could be a typical 110 volt, 60 hertz power outlet as is
commonly available in the United States or could be a large power
buss for charging cells in bulk. The power buss 12 is linked to a
high power factor corrector 14 which may be a large coil or active
corrector to bring the power factor to 1. For example, one may use
a uc3854 manufactured by Texas Instruments or any similar device.
The power is then supplied to an DC to DC converter 16 such as a
uc3825 manufactured by Texas Instruments to prepare the DC power
for use by the charging circuit.
[0034] Should the parallel battery charging device 20 be intended
for use on a mobile vehicle, the components of the power source 10
may all be disposed separate from the vehicle. Such a configuration
would reduce the overall weight of the vehicle and allow any
properly chosen direct current source, including an offboard
battery or solar energy source, to be used to charge the onboard
batteries.
[0035] Alternatively, should ground support equipment be
unavailable, the high power factor corrector 14 and an DC to DC
converter 16 may be disposed in the vehicle to allow charging from
any proper source of alternating current as noted above.
[0036] The power source 10 is connected to a high frequency source
18 to generate a high frequency waveform for use by a transformer.
The waveform may be a pulse or square-wave generated by a LT 1162
Pulse Width Modulator and LT 1846 Integrated Circuit manufactured
by Linear Technologies or equivalent. The operating frequency of
the high frequency source may range from 20 KHZ. to 1,000 KHZ.
[0037] The high frequency source 18 supplies a multi-winding
transformer for distribution to several battery cells for charging.
A transformer is an electrical device that is used for the
transmission and distribution of electrical energy. In principle, a
transformer consists of a plurality of coils magnetically coupled
to each other. One of the coils, known as a primary winding,
receives electrical energy, which is converted to purely magnetic
energy; the energy is continuously being delivered to the other
coil, known as a secondary winding, in electrical form. A
multi-winding transformer has two or more secondary windings on the
same core. A four-winding transformer (shown in FIG. 1), for
example, has a primary winding 22 and three secondary windings 24a,
24b, and 24c.
[0038] The primary winding or input coil 22 provides the electrical
energy to create the magnetic flux in an induction core 21. Due to
the magnetic coupling, a time-varying excitation applied to the
primary winding 22 induces a similar time varying response in the
secondary windings 24a-c. The transformer used for this application
is a prototype design produced by Zinc Air Power Corporation of
Strongsville, Ohio using common ferrite materials and conventional
means as known in the art. Each secondary winding 24a, 24b, and 24c
is isolated from one another and from the input coil 22. This
isolation permits each battery cell charging circuit to draw the
proper current for each of a plurality of battery cells 40a, 40b,
and 40c. The three circuits are isolated so that the current draw
of each battery cell does not affect the charging of the other
cells.
[0039] The output coils 24a, 24b, and 24c are connected to a number
of regulators 26a, 26b, and 26c respectively. The regulators 26a-c
each convert the high frequency electrical energy back to a DC
supply current at a voltage between 1.00 and 2.5 volts and regulate
the current as required by each battery cell 40a-c. The isolation
between the charging circuits allows independent control of the
battery charging current and voltage. The regulators may be as
simple as a diode placed between the output coil and the charging
electrode or may be an active circuit. Using the simple diode form,
cell charge balance is possible where each cell will draw it's
portion of magnetic energy inversely proportional to it's state of
charge. Each regulator 26a, 26b, and 26c is connected to the each
of the battery cells 40a, 40b, and 40c via a number of cables 28a,
28b, and 28c wired in parallel. The positive output of each
respective regulator 26a-c is attached to a charge electrode 44a-c
of each of the three battery cells 40a-c. The negative or common
lead of each respective regulator 26a-c is attached to a negative
or common electrode 42a-c of each of the three battery cells
40a-c.
[0040] FIG. 1 also includes a diagramatic view of a tri-electrode
battery 30 incorporating three independent battery cells 40a, 40b,
and 40c connected in series using two series connectors 36. While
the tri-electrode battery 30 shows three cells, any number of cells
may be used to fit the application. Each cell 40a, 40b, and 40c of
the tri-electrode battery 30 incorporates three electrodes.
Referring specifically to battery cell 40a, a first or common
electrode 42a is identified as synonymously with a negative
terminal 34. The common electrode 42a is used for both charging in
"parallel" and discharging in "series." In addition to the common
electrode 42a, battery cell 40a includes a discharge electrode 46a.
The discharge electrode 46a performs the normal electrochemical
discharge function as in a conventional bi-electrode battery; it
plays no role in electrochemical charging, thereby enhancing its
life.
[0041] Unique to cell 40a of the tri-electrode battery 30 is an
independent charge electrode 44a, which may be made in accordance
with the metal-air battery invention disclosed in U.S. patent
application Ser. No. 09/552,870. In that patent application, the
third electrode of the battery cell may be positioned between the
air electrode and the metal electrode. Alternatively, the metal
electrode of the battery cell may be positioned between the air
electrode and the third electrode to further increase in the power
output of the battery cell by permitting an open separator to be
used between the air electrode and the metal electrode.
[0042] The remaining structure of a typical tri-electrode battery
cell is conventional in nature and is known to those skilled in the
art. For example, see: Metal-Air Batteries by D P Gregory, BSG,
PhD, published by Mills & Boon Limited, copyright 1972, which
discloses secondary metal-air cells and is incorporated herein by
reference.
[0043] The third electrode of the tri-electrode battery 30 contains
numerous openings which permit the free flow of ions from the
electrolyte between the air electrode and the metal electrode
during the discharge cycle.
[0044] By charging any conventional battery using the parallel
battery charging device 20, the need to disconnect the series
connectors 36 is eliminated. Such a configuration is shown in FIG.
2 where the parallel battery charging device 20 is used to charge a
conventional two-electrode, multi-cell battery 38 with series
connections 36 connected. The parallel battery charging device 20
saves operator time (the series connections do not have to be
disconnected) and reduces mechanical wear on the intra-battery
terminals 42abc and 46abc.
[0045] Further, each battery cell 40abc may draw its optimum
electrical current during the charging cycle independent of the
other battery cells being charged. The present invention eliminates
one of the major drawbacks of electrochemical charging the battery
cells in series; they all receive the same current throughout the
charging cycle.
[0046] FIGS. 3A and 3B show typical graphs representing the charge
cycles of two different multi-cell batteries. FIG. 3A shows a 32
ampere-hour nickel-cadmium set of cells that are unbalanced by 10
ampere-hours. Cells labeled 1 and 3 have a 10 ampere-hour charge at
the beginning of the charge cycle. Cells labeled 2 and 4 are
essentially discharged at the beginning of the charge cycle. The
parallel battery charging device 20 provides balanced charging
current to each cell during the charging cycle.
[0047] FIG. 3B shows a typical charging cycle of the parallel
battery charging device 20 being used to charge six zinc-air cells
incorporating a third electrode in accordance with the present
invention. Specifically, this multi-cell battery containing the
third electrode was subjected to 3 complete charge/discharge
cycles. Each of the six charging curves in FIG. 3B show the
charging voltage during the charge cycle.
[0048] In operation, while the induction core 21 isolates each
battery charging circuit and the regulators 26abc monitor the
voltage in each circuit, overall control of the charging device 20
is governed by a charge controller 50. The charge controller 50 may
include two features: a top-off timer 54 and a current sensor 52.
The top-off timer 54 provides an upper limit on the time for which
the charger is applied to the battery cells. After the charge cycle
proceeds for a predetermined period, the top-off timer 54 can
terminate the charging process to prevent battery cell damage.
Further, the current sensor 52 can monitor the total current
provided to the input coil 22 and the charge controller 50 can
terminate the charging process when the current draw required to
the input coil 22 falls below a predetermined level.
[0049] In addition to the capability of parallel charging of
individual battery cells of a tri-electrode battery, the present
invention may be used to charge separate conventional batteries in
parallel. As shown in FIG. 4, the parallel battery charging device
20 may be used to charge conventional two-terminal batteries 47abc,
regardless of the number of cells comprising the battery. Each
battery may be coupled via an individual regulator 26 and cable 28
in the same manner as the battery cells 40a-c of FIG. 1. The
charging method maintains the same isolation properties to each
charging circuit as are obtained when charging the tri-electrode
battery cells.
[0050] Moreover, if the battery charging device is incorporated
onto a vehicle, the system may further include a braking energy
recovery device 58. Such a device converts the vehicle's kinetic
energy into electrical energy by mechanically or electrically
engaging a generator to the vehicle's drive-train upon application
of the brakes. Typically, such a device is the vehicle's drive
motor operated in reverse. Such a device assists the vehicle
braking with the mechanical load of the generator while providing
an electric current to the high frequency source 18 or into the DC
to DC converter 16 if the device's output is alternating current.
In any event, the device operates to recycle kinetic energy into
electrochemical storage in the battery rather than to allow the
energy to dissipate as heat.
[0051] In another embodiment shown in FIG. 5, the current levels
I.sub.1, I.sub.2, and I.sub.3 and the voltages V.sub.1, V.sub.2,
and V.sub.3 are detected at each cell 40a, 40b, and 40c. The
voltage and current levels provide feedback input to the controller
50 that controls the DC supply 60 to the high frequency source 18.
This configuration provides an extensive number of ways to control
the charging including statistical analysis on the cells'
comparative health. If the characteristic voltage and current
levels of a damaged cell are known, the damaged cell may be
identified and the charging level is controlled accordingly or the
cell is replaced as necessary. Additionally with such a
configuration, it is possible to simultaneously charge and
discharge individual cells.
[0052] Although the invention has been shown and described with
respect to a certain preferred embodiment or embodiments, it is
obvious that equivalent alterations and modifications will occur to
others skilled in the art upon the reading and understanding of
this specification and the annexed drawings. In particular regard
to the various functions performed by the above described
components (assemblies, devices, circuits, etc.), the terms used to
describe such components are intended to correspond, unless
otherwise indicated, to any component which performs the specified
function of the described component. In addition, while a
particular feature of the invention may have been disclosed with
respect to only one of several embodiments, such feature may be
combined with one or more other features of the other embodiments
as may be desired and advantageous for any given or particular
application.
* * * * *