U.S. patent application number 09/982860 was filed with the patent office on 2002-04-25 for method, arrangement and interface system to enable electrical batteries of different kinds to be charged by means of the same charger device.
This patent application is currently assigned to ALCATEL. Invention is credited to Perelle, Michel.
Application Number | 20020047685 09/982860 |
Document ID | / |
Family ID | 8855596 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020047685 |
Kind Code |
A1 |
Perelle, Michel |
April 25, 2002 |
Method, arrangement and interface system to enable electrical
batteries of different kinds to be charged by means of the same
charger device
Abstract
A method enabling balanced charging of batteries that have
voltages of the same order of magnitude and which can be of
different kinds uses a charger device to provide at least one
constant regulation voltage appropriate to a battery, in an
arrangement including a system composed of individual interfaces
associated with respective rechargeable cells constituting the
battery and a common interface. The individual interfaces provide
the common interface with an indication relating to the voltages
that they measure at the terminals of the associated cell. The
common interface produces a signal controlling switching of a
battery charging characteristic between two characteristics when
one of the measurement circuits determining the voltage present at
the terminals of the rechargeable cells reports that a maximum
balancing threshold value is exceeded.
Inventors: |
Perelle, Michel;
(Parcay-Meslay, FR) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
Suite 800
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3213
US
|
Assignee: |
ALCATEL
|
Family ID: |
8855596 |
Appl. No.: |
09/982860 |
Filed: |
October 22, 2001 |
Current U.S.
Class: |
320/119 |
Current CPC
Class: |
Y02T 10/7005 20130101;
Y02T 10/7061 20130101; B60L 58/22 20190201; Y02T 10/70 20130101;
Y02T 10/7044 20130101; H02J 7/0016 20130101; H02J 7/00
20130101 |
Class at
Publication: |
320/119 |
International
Class: |
H02J 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2000 |
FR |
00 13 512 |
Claims
There is claimed:
1. A method of charging an electrical battery by means of a charger
device able to supply at least one appropriate constant regulation
voltage to the battery to be charged, regardless of the nature of
the rechargeable cells constituting said battery, provided that
said battery has a nominal voltage compatible with said regulation
voltage or voltages that said charger device supplies, said method
including the following steps: continuously measuring the voltage
at terminals of each rechargeable cell of said battery; activating
an associated individual shunt circuit connected in parallel with
each rechargeable cell as soon as the voltage measured at said
terminals of said rechargeable cell exceeds a particular regulation
minimum threshold value fixed as a function of the nature of said
rechargeable cell and for as long as said measured voltage is above
said minimum threshold value; supplying an indication as to whether
a balancing maximum threshold value fixed as a function of the
nature of a rechargeable cell is exceeded or not by said voltage
measured at said terminals of said rechargeable cell; translating
into the form of a single binary signal respective indications as
to whether said maximum threshold is exceeded or not obtained for
each of said rechargeable cells at a given time, said single signal
being maintained at a first binary value for as long as none of
said voltages measured at said terminals of said rechargeable cells
of said battery exceeds said maximum threshold value and at a
second value otherwise; and translating said single signal obtained
from said indications as to whether said maximum threshold is
exceeded or not into a signal controlling switching of a battery
charging characteristic between two characteristics that can be
selected either directly at the charger device or via an auxiliary
device associated therewith.
2. The method claimed in claim 1 wherein said charge characteristic
switching control signal operates on a power switching function of
said charger device or included in an auxiliary device disposed
between said charger device and its power supply to enable the
supply of charging current to said battery if said respective
voltages measured at said terminals of said rechargeable cells are
below said balancing maximum threshold value and to stop the supply
of charging current to said battery as soon as the voltage measured
at the terminals of one of said rechargeable battery cells exceeds
said maximum threshold value.
3. The method claimed in claim 1 wherein said charge characteristic
switching control signal controls the substitution of one charge
regulation voltage for another in said charger device to control
switching from the higher to the lower of said two regulation
voltages if said voltage measured at said terminals of a
rechargeable battery cell exceeds said balancing maximum threshold
value and to switch from said lower to said higher regulation
voltage if said respective voltages measured at said terminals of
said rechargeable cells are below said balancing maximum threshold
value.
4. An arrangement including a battery made up of rechargeable cells
connected in series and a charger device able to provide at least
one constant regulation voltage for charging said battery, which is
associated with: an individual interface for each rechargeable cell
of said battery, including a first voltage measuring circuit
connected to terminals of the rechargeable cell concerned to
control a current shunt circuit connected in parallel with it in
order to shunt at least some of the charging current that is
supplied to it if said voltage measured at said terminals of said
rechargeable cell exceeds a particular regulation minimum threshold
value fixed as a function of the nature of said cell, said
individual battery interfaces each including a second voltage
measuring circuit for determining if a balancing maximum threshold
value is exceeded at said terminals of the associated rechargeable
cell to which said individual interface is assigned, on the basis
of a voltage measured across a measuring resistor in series with
said shunt device of said interface between said terminals of said
associated rechargeable cell, and a circuit constituting a
transmission AND logic gate which transmits a binary indication as
to whether said balancing maximum threshold value is exceeded or
not at said terminals of said associated rechargeable cell; a
common interface to which said individual interfaces are connected
and to which each supplies at least one indication of said measured
voltage for the associated rechargeable cell, said indication being
used to control charging by said charger device, said common
interface translating any indication relating to said balancing
maximum threshold value being exceeded supplied to it by means of a
transmission chain into which said transmission gates of said
individual interfaces are inserted in series in the form of a
charge characteristic switching control signal; and a charger
device which has at least one battery charge characteristic which
is modified either in said charger device itself or in an
associated auxiliary device as a function of said characteristic
switching control signal.
5. The arrangement claimed in claim 4 wherein said signal
indicating that a threshold value is exceeded which is supplied to
said common interface via said serial transmission chain has a
binary value of 1 if respective indications as to whether said
threshold is exceeded or not supplied by said transmission gates of
said individual interfaces reflect the fact that said voltages at
said terminals of said cells of said battery by said measuring
circuits of said individual interfaces are below said balancing
maximum threshold value fixed for said cells constituting said
battery.
6. The arrangement claimed in claim 4 wherein modifying said charge
characteristic as a function of said switching control signal cuts
off said charge current supplied by said charger device to said
battery if an individual interface determines that the voltage at
said terminals of a battery cell is above said balancing maximum
threshold value fixed for each cell of said battery, said charging
current being supplied if it is determined that no voltage at said
terminals of a cell exceeds said threshold value.
7. The arrangement claimed in claim 4 wherein modifying the charge
characteristic as a function of said switching control signal
changes from one value to the other of said regulation voltage
produced by said charger at the end of charging a battery, a change
from said higher value to said lower value being effected if an
individual interface determines that a voltage at said terminals of
a battery cell exceeds said balancing maximum threshold value fixed
for each cell of said battery, and the reverse change being
effected if it is determined that no voltage at said terminals of
one of said cells exceeds said threshold value.
8. An interface system for a battery made up of rechargeable cells,
which system includes: an individual interface for each
rechargeable battery cell, each individual interface including a
voltage measuring circuit connected to terminals of one of said
rechargeable cells to control a current shunt circuit connected in
parallel with said cell in order to shunt at least some of the
charging current applied to it if the voltage measured at said
terminals of said cell exceeds a particular regulation minimum
threshold value fixed as a function of the nature of said cell,
said individual battery interfaces each including a second voltage
measuring circuit for determining if a balancing maximum threshold
value is exceeded at said terminals of the associated rechargeable
cell, to which said individual interface is assigned, on the basis
of a voltage measured across a measuring resistor in series with
said shunt device of said interface between said terminals of said
associated rechargeable cell, and a circuit constituting a
transmission logic AND gate which transmits a binary indication as
to whether said balancing maximum threshold value is exceeded or
not at said terminals of said associated rechargeable cell; and a
common interface to which said individual interfaces are connected
for each to supply at least one indication relating to the voltage
measured for said associated rechargeable cell, said indications
being used by a charger device to control charging, said common
interface translating any indication relating to said balancing
maximum threshold value being exceeded, supplied to it by means of
a transmission chain into which said transmission gates of said
individual interfaces are inserted in series, in the form of a
charge characteristic switching control signal for use by a charger
device either directly or via an associated auxiliary device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on French Patent Application No.
00 13 512 filed Oct. 23, 2000, the disclosure of which is hereby
incorporated by reference thereto in its entirety, and the priority
of which is hereby claimed under 35 U.S.C. .sctn.119.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a method, an arrangement and
interface system for charging electrical batteries that supply
voltages of the same order and which are composed of rechargeable
cells which can be of different kinds from one battery to another.
It uses a charger device able to supply at least one constant
regulation voltage suitable for a battery. It aims to protect the
cells of a battery against overvoltages likely to occur during
charging.
[0004] The arrangement envisaged is of the type which temporarily
substitutes a battery for another power supply to power a load
circuit if that other supply is temporarily unable to do so. The
previously charged battery remains on permanent "floating" charge,
for example, if the other supply is operating. This kind of
arrangement routinely combines a battery, a device for charging the
battery from a supply, and a load circuit, all of which are
permanently interconnected. This configuration is used with
telecommunication equipment that is intended to operate without
interruption, for example.
[0005] The arrangement can also be organized differently, so that
the battery, which can power a load circuit, can be charged
intermittently from a supply via a charger device. The latter can
top up the charge, using the technique referred to above, when the
supply is operating. This is the case, for example, if the battery
is that of an arrangement including a charger device that is
powered by a supply rendered active on demand and/or as and when
required, as in an electric vehicle. Descrirtion of the prior art
Arrangements of the above kind are routinely equipped with means
for balancing the various rechargeable cells that constitute a
battery, for optimum management over time. Such means are disclosed
by European patent 121 547, among others.
[0006] There are many devices for charging a battery which supply a
predetermined regulation voltage. There are also many devices
providing the facility to select one or more of a number of
regulation voltages, in particular for charging different
batteries.
[0007] Because of the standardization of rechargeable batteries and
non-rechargeable dry cells, it is often possible to power the same
equipment, by supplying it with a sufficient voltage for it to
operate, by means of a battery, that is to say a particular system
of cells of the same kind, rechargeable or not, chosen from a range
of systems, as a function of the requirements of the user and/or
what is available in terms of batteries at the time in question.
The battery cells that can be substituted for each other are
lead-acid cells, alkaline cells and lithium cells, for example.
[0008] However, to be really advantageous, this substitution
facility implies that users can charge at least some of the
different kinds of batteries using the same device, rather than
using individual devices each suitable for a different battery. The
necessity to have different charger devices has undoubted drawbacks
for users wishing to be able to use batteries of different kinds,
in place of each other, as a function of what they require or what
is available at the time, to power the same load circuit in the
context of a particular arrangement.
[0009] The skilled person knows that the overvoltages likely to
occur during charging can have a harmful effect on the battery
cells subjected to them, especially if the cells are more sensitive
to overvoltages than other kinds of cell, as is the case with
lithium cells, for example.
[0010] It is therefore necessary to take precautions if it is
intended to charge a battery using a device designed for another
battery, based on the fact that the battery has substantially the
same nominal voltage.
[0011] The skilled person knows that a voltage step-up/step-down
unit can be added to the electrical circuit connecting a charger
device to a battery if the latter is supervised by a management
circuit which transmits a control signal to the voltage
step-up/step-down unit to modify the voltage supplied to the
battery. The unit reduces the voltage when a battery cell is
overcharged. However, this kind of additional component is costly
and may be a problem if no space is provided for it on the battery
or the charger device.
[0012] The skilled person also knows that a charger device, for
example an individual charger of the usual kind for lead-acid
batteries, can be used to charge batteries of a different kind if
it is possible to modify the regulation voltage supplied by the
device to prevent all risk of overvoltage at each of the cells of
the battery being charged.
[0013] There are charger devices designed to receive an analog
regulation voltage control signal. However, this kind of charger
device can be used only with a battery to be charged which is
associated with an interface providing an appropriate analog
control signal. This kind of interface has drawbacks that
correspond to those of an additional voltage step-up/step-down unit
and requires a power supply to meet its requirements.
[0014] In some arrangements in which a battery is used in
association with a charger device, there is also provided a circuit
connected in parallel with each rechargeable cell to divert at
least some of the current that is supplied to the battery by the
charger device and which flows in that cell if the voltage measured
at the terminals of the cell by an associated measuring circuit
exceeds a particular threshold value.
[0015] An arrangement of this kind is specifically disclosed in
European patent 121 547, referred to above. Its components can be
physically associated in modular form with the rechargeable battery
cell to which they are assigned, or possibly a group of such cells,
in an autonomous hardware unit. This kind of unit can be connected
in series with at least one other identical autonomous unit to form
a battery in which balancing is ensured cell by cell.
SUMMARY OF THE INVENTION
[0016] The invention proposes a method of charging an electrical
battery by means of a charger device able to supply at least one
appropriate constant regulation voltage to the battery to be
charged, regardless of the nature of the rechargeable cells
constituting the battery, provided that the battery has a nominal
voltage compatible with the regulation voltage or voltages that the
charger device supplies, the method including the following
steps:
[0017] continuously measuring the voltage at terminals of each
rechargeable cell of the battery;
[0018] activating an associated individual shunt circuit connected
in parallel with each rechargeable cell as soon as the voltage
measured at the terminals of the rechargeable cell exceeds a
particular regulation minimum threshold value fixed as a function
of the nature of the rechargeable cell and for as long as the
measured voltage is above the minimum threshold value;
[0019] supplying an indication as to whether a balancing maximum
threshold value fixed as a function of the nature of a rechargeable
cell is exceeded or not by the voltage measured at the terminals of
the rechargeable cell;
[0020] translating into the form of a single binary signal
respective indications as to whether the maximum threshold is
exceeded or not obtained for each of the rechargeable cells at a
given time, the single signal being maintained at a first binary
value for as long as none of the voltages measured at the terminals
of the rechargeable cells of the battery exceeds the maximum
threshold value and at a second value otherwise; and
[0021] translating the single signal obtained from the indications
as to whether the maximum threshold is exceeded or not into a
signal controlling switching of a battery charging characteristic
between two characteristics that can be selected either directly at
the charger device or via an auxiliary device associated
therewith.
[0022] The invention also proposes an arrangement including a
battery made up of rechargeable cells connected in series and a
charger device able to provide at least one constant regulation
voltage for charging the battery, which is associated with:
[0023] an individual interface for each rechargeable cell of the
battery, including a first voltage measuring circuit connected to
terminals of the rechargeable cell concerned to control a current
shunt circuit connected in parallel with it in order to shunt at
least some of the charging current that is supplied to it if the
voltage measured at the terminals of the rechargeable cell exceeds
a particular regulation minimum threshold value fixed as a function
of the nature of the cell, the individual battery interfaces each
including a second voltage measuring circuit for determining if a
balancing maximum , threshold value is exceeded at the terminals of
the associated rechargeable cell to which the individual interface
is assigned, on the basis of a voltage measured across a measuring
resistor in series with the shunt device of the interface between
the terminals of the associated rechargeable cell, and a circuit
constituting a transmission AND logic gate which transmits a binary
indication as to whether the balancing maximum threshold value is
exceeded or not at the terminals of the associated rechargeable
cell;
[0024] a common interface to which the individual interfaces are
connected and to which each supplies at least one indication of the
measured voltage for the associated rechargeable cell, the
indication being used to control charging by the charger device,
the common interface translating any indication relating to the
balancing maximum threshold value being exceeded supplied to it by
means of a transmission chain into which the transmission gates of
the individual interfaces are inserted in series in the form of a
charge characteristic switching control signal; and
[0025] a charger device which has at least one battery charge
characteristic which is modified either in the charger device
itself or in an associated-auxiliary device as a function of the
characteristic switching control signal.
[0026] The invention further proposes an interface system for a
battery made up of rechargeable cells, which system includes:
[0027] an individual interface for each rechargeable battery cell,
each individual interface including a voltage measuring circuit
connected to terminals of one of the rechargeable cells to control
a current shunt circuit connected in parallel with the cell in
order to shunt at least some of the charging current applied to it
if the voltage measured at the terminals of the cell exceeds a
particular regulation minimum threshold value fixed as a function
of the nature of the cell, the individual battery interfaces each
including a second voltage measuring circuit for determining if a
balancing maximum threshold value is exceeded at the terminals of
the associated rechargeable cell, to which the individual interface
is assigned, on the basis of a voltage measured across a measuring
resistor in series with the shunt device of the interface between
the terminals of the associated rechargeable cell, and a circuit
constituting a transmission logic AND gate which transmits a binary
indication as to whether the balancing maximum threshold value is
exceeded or not at the terminals of the associated rechargeable
cell; and
[0028] a common interface to which the individual interfaces are
connected for each to supply at least one indication relating to
the voltage measured for the associated rechargeable cell, the
indications being used by a charger device to control charging, the
common interface translating any indication relating to the
balancing maximum threshold value being exceeded, supplied to it by
means of a transmission chain into which the transmission gates of
the individual interfaces are inserted in series, in the form of a
charge characteristic switching control signal for use by a charger
device either directly or via an associated auxiliary device.
[0029] The invention, its features and its advantages are explained
in the following description, which is given with reference to the
single figure of the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0030] The single figure of the accompanying drawing is a circuit
diagram of one example of an arrangement in accordance with the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] The arrangement includes an electric battery 1, a device 2
for charging the battery from a supply, not shown, and a load
circuit 3 that is powered by the battery and can be connected to
the supply or not.
[0032] The battery is of modular design and constitutes a system
combining a series of modules connected in series, each module
consisting of at least one rechargeable cell 5. To simplify the
description, the remainder of the application refers only to
rechargeable cells, on the understanding that the invention can be
used with rechargeable cells grouped into modules, as indicated
above.
[0033] The battery 1 shown has two end terminals B+ and B- between
which three rechargeable cells 5 are connected in series.
[0034] The charger device 2 is supplied with electrical power from
a supply, not shown, for example an electrical power distribution
network or an independent electrical power generator. The charger
device 2 is connected to the end terminals of a battery to be
charged via connection members C1+ and C1-.
[0035] In the embodiment shown, the load circuit 3 which the
battery 1 powers is connected to the battery via connection members
C2+ and C2-.
[0036] The connection members referred to above can be of types
known to the skilled person and are therefore not described in
detail here. The load circuit 3 is a functional equipment unit of
an independent device or system, for example.
[0037] The arrangement envisaged can charge the battery 1 by means
of the charger device 2 whilst also powering the load circuit 3, if
required and if the charger device and the power supply circuit are
connected simultaneously to the end terminals of the battery.
[0038] As indicated in the preamble, the use of different batteries
is envisaged, depending on the requirements of the user or the
availability in terms of batteries at the time, using a charger
device and in particular in the context of an arrangement according
to the invention. The charger device provides at least one
particular charging characteristic. That characteristic corresponds
to a particular regulation voltage, for example. The batteries have
respective nominal voltages appropriate to the voltage or voltages,
in particular the regulation voltage or voltages, that the charger
device can supply.
[0039] For example, substituting a 48 volt battery made up of
lithium cells for a battery made up of lead-acid cells or alkaline
cells can be envisaged, and is one situation in which the numbers
of cells in the two batteries is not the same.
[0040] In this case, each rechargeable lithium cell 5 of the
battery is shunted by a shunt circuit. If the voltage measured at
the terminals of a rechargeable cell rises above a particular
balancing minimum threshold value V1, each shunt circuit shunts at
least some of the current supplied to the battery by the charger
device 2 and which flows in that cell. The threshold value is fixed
as a function of the nature of the rechargeable cells.
[0041] In a preferred embodiment, the shunt circuit of each
rechargeable cell 5 of a battery is incorporated into an individual
interface 6 associated with the cell. The individual interfaces are
connected in common to a common interface 7, for example by a
daisychain connection, as shown in the figure.
[0042] Each individual interface 6 further includes means for
implementing the method according to the invention in cooperation
with the common interface 7.
[0043] The shunt circuit of each individual interface operates in
accordance with the principle described in European patent 121 547,
referred to above, for example, as succinctly explained below. A
first voltage measuring circuit 8 is connected to the terminals of
the rechargeable cell 5 via a measuring resistor 9 connected to the
negative terminal of the cell.
[0044] The measuring circuit 8 of an individual interface 6 is of
the kind described in the European patent cited above; it therefore
controls the connection into circuit of a shunt branch consisting
of a resistor 10 and a transistor 11, here connected in series with
the measuring resistor 9, between the terminals of the rechargeable
cell 5 with which the interface is associated. The skilled person
knows that no current flows through the shunt branch if the voltage
v evaluated by the measuring circuit 8 has not reached a value v1
for which the voltage at the terminals of the rechargeable cell 5
is equal to the minimum threshold value V1. As soon as the value v1
is exceeded, the measuring circuit commands the transistor 11 to
divert into the shunt branch some of the current supplied to the
rechargeable cell by the charger device. The shunted current
increases progressively if the image voltage v evaluated by the
measuring circuit 8 reflects a progressive increase in the voltage
at the terminals of the rechargeable cell 5.
[0045] According to the invention, each individual interface 6
includes a second voltage measuring circuit 12 which supplies the
common interface 7 with a binary indication relating to the voltage
at the terminals of the rechargeable cell 5 of the battery 1 it is
monitoring. That indication is preferably a binary 0 if the voltage
at the terminals of the cell 5 exceeds a particular balancing
maximum threshold value V2 greater than the minimum threshold value
V1. The maximum threshold voltage V2 is chosen to be less than or
at most equal to the maximum voltage Vm permitted at the terminals
of one of the rechargeable cells that constitute the battery 1, the
voltages V2 and Vm being fixed as a function of the nature of the
cells that constitute the battery. In a preferred embodiment,
non-exceeding and exceeding of the threshold respectively
correspond to a binary 1 signal and a binary 0 signal. The
indication supplied by a measuring circuit 12 is transmitted from
the individual interface 6 which includes the circuit to the common
interface 7 via a circuit that constitutes a transmission gate 13
and has a logic AND function.
[0046] Each transmission gate 13 has a first input at which it
receives the indication supplied by the measuring circuit 12 of the
individual interface that includes it and a second input referred
to as a chaining input. The chaining input of a transmission gate
of an individual interface is connected to the output of the
transmission gate that precedes it in the chain, the chaining input
of the interface at the head of the chain systematically receiving
a binary 1 signal. Consequently, the transmission gate 13 of the
head individual interface must produce a binary 1 signal at its
output if no indication of a threshold being exceeded is received
from the measuring circuit 12 to which it is connected, because in
this case both of its inputs receive a binary 1 signal. Likewise
for the transmission gates 13 of the subsequent individual
interfaces of the chain, if no indication of a threshold being
exceeded is supplied by the respective measuring circuits 12 of
those interfaces, a binary 1 signal is supplied to the common
interface 7. In practice this signal is reflected in the flow of a
current along the chain connecting the individual interfaces to the
common interface.
[0047] In the embodiment shown by way of example, the positive
potential at the positive terminal B+ of the battery 1 is therefore
applied to the chaining input of the transmission gate 13 of the
individual interface 6 at the head of the chain. The chain is
obtained by series connection of the individual interfaces 6 which
each have a chain input terminal D1 and a chain output terminal D2
between which the transmission gate 13 of the interface is
connected. The indication by a measuring circuit 12 that a
balancing maximum threshold value V2 is exceeded at the terminals
of a cell 5 corresponds to the appearance of a binary 0 signal at
the first input of the transmission gate 13 controlled by that
measurement circuit and therefore at the output of that
transmission gate. The current previously flowing through the chain
connecting the individual interfaces to the common interfaces is
then interrupted. This solution also enables action on the charger
device if the continuity of the chain is broken, in the same manner
as if the balancing maximum threshold voltage V2 is exceeded.
[0048] The common interface 7 is designed to act through the
intermediary of a charge characteristic switching signal on a
switching function incorporated in or associated with the charger
device 2 to which it is connected. In a first embodiment, intended
for charger devices designed to provide a single constant
regulation voltage during battery charging, this function ensures
switching between a first position in which the charging current
that the charge device produces is applied to the battery if the
binary signal received by the common interface is a binary 1
signal, and a second position in which the current is no longer
supplied if the binary signal received by the common interface is a
binary 0 signal.
[0049] The resulting on/off operation can occur in the charger
device, which then includes appropriate switching means adapted to
be controlled via a control input 1, through the intermediary of
which the usual means, not shown here, are actuated as a function
of the value of the binary signal received by the common
interface.
[0050] This operation can also be obtained by acting on a switch
unit 14 external to the charger device. For example, the switch
unit is inserted between the charger device and a power
distribution network which powers the charger device, and is then
used to control the supply of power to the charger device on an
on/off basis. It can be incorporated into the common interface 7.
This kind of switch unit 15 can also be provided at the output of
the charger device, with the same aim of controlling the power
supplied to the battery to charge it, the unit being controlled by
the common interface 7, under the same conditions as the switch
unit 14 envisaged above.
[0051] A battery 1 is charged by the charger device 2 defined above
if the voltage at the terminals of each of the rechargeable cells 5
constituting the battery is below the maximum threshold value V2
that is fixed at exactly the same value by the individual
interfaces for each rechargeable cell. Each rechargeable cell 5
receives the current supplied at constant voltage by the charger
device if that current is present and is not at least partly
shunted by the shunt circuit associated with that cell.
[0052] The shunt circuit of any rechargeable battery cell at whose
terminals the measured voltage exceeds the minimum threshold value
V1 continues to operate. It partially discharges the rechargeable
cell, and this discharge can continue until the voltage measured at
the terminals of that rechargeable cell falls below the minimum
threshold value V1.
[0053] The battery is therefore balanced by discharging the most
heavily charged cells. As soon as the voltages measured at the
terminals of the cells of the battery 1 are all below the maximum
threshold value V2, the serial transmission chain between the
individual interfaces is reestablished and is used to control the
charger device via the common interface 7 so that it again supplies
a charging current to the battery, to which it applies the constant
regulation voltage previously applied.
[0054] The charging of a battery is reflected in a succession of
phases of charging its cells interleaved with phases during which
the battery is slightly discharged because of the consumption of
energy by the load circuit that it powers and/or the operation of
the shunt circuits associated with the cells of the battery. Each
cell of the battery is therefore balanced by being charged during
phases in which the charger is rendered active and by being
discharged during phases in which the charger is rendered inactive.
If balancing is done well, operation of a load circuit at a
constant "floating" voltage can be obtained when the battery is
charged. This "floating" operation can be obtained permanently in
the context of an arrangement in which the charger device is in
service and connected to a battery and a load device permanently.
It can also be obtained during phases in which the charger device
is in service and connected at least to the battery, in the context
of an arrangement in which the charger device is activated only
intermittently.
[0055] In a second embodiment, the charger device 1 provides two
constant regulation voltages Vr1 and Vr2 rather than only one, in
particular at the end of charging. The two voltages can usually be
obtained by means provided as standard in the charger device, and
the control input 1 is then used to control the means, not shown,
for switching from one voltage to the other.
[0056] Once again the batteries, of different kinds, are associated
with individual interfaces 6 and with a common interface 7 for
charging them by means of a charger device 2. As previously, as
long as the voltage measured at the terminals of each of the cells
of a battery remains below the minimum threshold value V1, the
transmission gates 13 of the individual interfaces 6 transmit a
binary 1 signal to the common interface 7. In contrast, if the
voltage measured at the terminals of a rechargeable battery cell
exceeds the maximum threshold value V2, the transmission chain is
interrupted and a binary 0 signal appears at the common
interface.
[0057] The change from 1 to 0 of the binary signal input to the
common interface is used to control the substitution of the higher
regulation voltage Vr2 obtained from the charger device 2 for
charging the battery for the lower regulation voltage Vr1, in
particular at the end of charging. The change from 0 to 1 of the
binary signal applied to the common interface via the serial
transmission chain is used to control switching in the reverse
direction from the voltage Vr1 to the lower voltage Vr2.
[0058] Under these conditions a battery is charged by a succession
of charging phases during which the battery is subjected to the
higher regulation voltage Vr2, as long as the voltages measured at
the terminals of the cells of the battery are below the minimum
threshold value V1. Those phases are interleaved with phases in
which the battery is subjected to a lower regulation voltage Vr1 as
soon as and for as long as the voltage measured at the terminals of
a rechargeable cell exceeds the maximum threshold value V2. As
already envisaged previously, depending on the choice made in terms
of the battery/charger device/load circuit arrangement, the charger
device 2 can be included in a power supply which can power the load
circuit in parallel, if required.
[0059] Also, the supply of charging current to the battery is
generally stopped in the second embodiment described above from the
moment at which the voltage measured at the terminals of a battery
rechargeable cell (or failing this of the battery) exceeds a limit
value, greater than the maximum threshold voltage, beyond which
overvoltages that could damage the battery cells are likely to
occur.
[0060] Balancing is effected under conditions similar to those
referred to above if the rechargeable cells of the battery are in
good condition. The charger device 2 can then operate continuously,
when it is connected to the battery. Successive switching from one
regulation voltage to the other is then effected under the control
of the measuring circuits assigned to the rechargeable cells that
constitute the battery.
* * * * *