GB1590375A

GB1590375A - Multi-cell battery systems

Info

Publication number: GB1590375A
Application number: GB24794/76A
Authority: GB
Original assignee: Chloride Group Ltd
Current assignee: Chloride Group Ltd
Priority date: 1977-08-30
Filing date: 1977-08-30
Publication date: 1981-06-03

Description

(54) MULTI-CELL BATTERY SYSTEMS (71) We, CHLORIDE GROUP LIMITED, a Company registered under the laws of England, of 52 Grosvenor Gardens, London SWiW OAU, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to multi-cell battery systems for supplying a main load at any one of a number of sub-divisions of full battery voltage, and generally for supplying an auxiliary load at a predetermined sub-division of the full battery voltage. Thus, for example, in a battery propelled bus having a battery of 360 volts capable of supplying a maximum traction current of 500-550 amperes representing nearly 200 kilowatts it may be desirable on the one hand to supply the main motors with current from any one or more of perhaps six equal portions of the battery under the control of an accelerator pedal, and at the same time to provide an auxiliary supply of perhaps a few kilowatts for each of power steering, power brakes and lighting at a substantially constant voltage.

It has been proposed to divide the battery into units and provide switching means for supplying the auxiliary supply from any one unit and for supplying the main motor from any one or more units.

As compared with series-parallel connections such an arrangement has the advantage that it renders possible an arithmetical progression of voltage whereas series parallel only makes possible a geometrical progression. Thus, for example, with the battery divided into units it is possible to supply for example three-quarters of the total voltage whereas with series parallel it is only possible to supply half or a quarter or other sub-divisions of the main voltage. On the other hand the sub-division of the battery raises the problem of unequal discharge of the several units and it is desirable, as has been proposed, to vary the choice of units connected to the motors so that current is taken from each in turn of the various battery units.

An object of the present invention is to provide an improved system of this type.

According to the present invention, in a multi-cell electric battery system for supplying a main load at any one of a number of subdivisions of the full battery voltage, in which the battery is divided into a number of double battery units each comprising two single battery units permanently connected in series and which includes for each single unit, a set of change-over contacts comprising a common contact and what will be termed inner and outer contacts connected respectively to opposite terminals of the single unit, the inner contacts of a double unit being connected together and to the junction of the positive terminal of one single battery unit and the negative terminal of the other, and the common contacts forming terminals of the double units and being connected in series across the main load terminals so as to supply the main load with different voltages corresponding to the voltage of different combinations of single units in series.

In one form of this invention, the system serves for also supplying auxiliary load terminals at a predetermined sub-division of the full battery voltage, in which case it includes doublepole contacts arranged to connect the auxiliary load terminals selectively to the terminals of each double battery unit, to supply the auxiliary load at twice the voltage of a single unit.

In a known system in which the battery is divided into units any number of which may be connected to the main load, the auxiliary supply cannot be connected to two or more battery units in series, since this would interfere with the selection of those units for the main load. With the arrangement in accordance with the invention the two single units of a double unit are permanently connected in series, without interfering with the ability to connect any number of single units to the main load, and thus it is possible to use double the voltage for the auxiliary supply.

Preferably the system includes a motor current conducting diode connected between the common contact and inner contact of each single unit so that, while the changeover contact is changing over, current from the other units through the motor can flow through the motor current conducting diode.

Where the system provides regenerative braking, it may include a regeneration current conducting diode connected between the common contact and outer contact of each single unit, so that, while the contact is changing over, a reverse regenerative braking current can continue to flow through the regeneration current conducting diode.

Each of the regeneration current conducting diodes may be connected in series with a resistor or inductor, or may be replaced by a zener diode.

In a further form of the invention, providing regenerative braking, the terminals of the load circuit are connected to the terminals of the battery through regeneration change-over contacts serving to disconnect them from the common contacts of the end battery units and connect them to all the double units in parallel through diodes permitting current to flow in each double unit only in a charging direction.

In one such system the load circuit includes a series wound motor having an armature and series field and a braking shunt field winding connected through a brake initiation contactor across the motor armature in opposition to the series winding. A resistor may be provided in series with the braking field winding and means for short circuiting and/or varying the effective value of such resistor to vary the braking. A further resistor may be connected across the double units in parallel, together with their diodes, to provide dynamic (though not regenerative) braking.

The invention may be put into practice in various ways but two specific embodiments will be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are circuit diagrams respectively of two different forms of battery system for a battery-driven bus.

The bus has a battery totalling 360 volts divided into three double units 11 each comprising a pair of single units 12 of 60 volts connected in series by a junction 14.

For supplying an auxiliary load of for example 3 to 4 kilowatts for power steering, 2 to 3 kilowatts for power brakes, and 2 kilowatts for lighting at a voltage of 120 volts, each double unit is provided with double pole contacts 20 for connecting the auxiliary load terminals 21 selectively to each double battery unit.

In addition, for supplying the main load selectively, under the control of an accelerator pedal, with traction current at any multiple of 60 volts up to the full voltage of 360, each single unit is provided with change-over contacts 30,31, and 32, comprising a common contact 30 forming a terminal of the double unit, and inner and outer contacts 31 and 32 connected respectively to opposite terminals of a single unit. The two inner contact of a double unit are connected together and to the junction 14 between the positive terminal of one single battery unit and the negative terminal of the other.

The common terminals 30 of the double units are connected in series between the terminals 35 of a main load shown as a motor 36. Thus by selectively operating the change-over contacts any one or more of the single units may be included in the series circuit connected across the main motor terminals.

In order to suppress arcing, the inner contact 31 and common contact 30 of each changeover set are shunted by diode 38 permitting motoring main current to flow from the remaining battery units when the said contact is changing over, (the contacts being of break-beforemake type).

In addition, to provide for regenerative braking, a regeneration current conducting diode 39 is connected between each common contact 30 and the outer contact 32 to permit regenerative braking current to continue to flow when that contact is changing over. These diodes may be connected in series with resistors (not shown) in order not to suppress arcing completely but to allow a small spark to be produced in order to clean the contacts.

The change-over contacts are incorporated in contactors controlled by an accelerator pedal actuating a multi-pole selector switch, in conjunction with a uni-selector switch. In each position of the uni-selector the terminals of the accelerator switch are connected to the coils of the change-over contactors in a different combination. Thus as the accelerator is depressed with the uni-selector in its first position the contactors may be operated in the order 1,2,3,4, 5,6 and as the accelerator is released they will be released in the reverse order 6,5,4,3,2,1.

On returning to its released position the accelerator operates a contact serving to advance the uni-selector by one step, and, in its second position, the accelerator actuates the contactors in the order 2,3,4,5,6,1 and the reverse order 1,6,5,4,3,2. Thus each single unit of the battery will be first in its turn, second in its turn etc.

and in general a reasonably balanced distribution of discharge occurs throughout the battery.

Such control mechanism is of known type and is not shown in the drawings.

The unit-selector also controls the double pole contacts 20 for connecting the auxiliary load terminals to the double battery units. Preferably it is arranged so that the double battery unit supplying the auxiliary load will only be called upon to supply a share of the main load when the accelerator is fully depressed so that the likelihood of a particular battery unit having to supply auxiliary load and main load at the same time is reduced to a minimum. Alternatively, the double pole contactors 20 which connect the auxiliary load to one or other of the double battery units may be operated on a timed sequence e.g. once every 5 minutes, which is completely separate from the operation of the main traction controller.

Figure 2 shows a modified arrangement in rather more detail than Figure 1. As in the arrangement of Figure 1 the battery is divided into a number of double units 11, each comprising two single units 12 connected in series.

Each single unit is associated with a set of change-over contacts comprising inner and outer contacts 31 and 32 connected respectively to the terminals of the single unit, and a common contact 30. The common terminals of the several double units are connected in series. The main load comprises a series wound motor having an armature 50 and three series windings, 51, 52 and 53 two of which can be short circuited by means of field divert contactors 54 and 55 in order to vary the drive torque.

The armature is connected between the field and one motor terminal by reversing changeover contacts 57 serving to reverse its connection in the circuit.

Instead of being connected directly to the battery terminals 34 the motor terminals 35 are connected to them through change-over contacts, each comprising a common contact 61 and motor and regenerating contacts 62 and 63 of which the two motor contacts are connected to the terminals of the battery. The regenerating contacts on the other hand are connected to each double unit of the battery in parallel, through diodes 64 allowing current to flow through each double unit only in a charging direction.

The motor-regenerating contacts are arranged to changeover to the regenerating position whenever the accelerator pedal is released. In these circumstances, there would be no current in the motor and hence no excitation from the series windings.

Accordingly, a braking shunt winding 70 is arranged to be connected through a brake initiation contactor 71 across the terminals of the armature, and when this contactor is closed the residual field will be sufficient to build up an armature voltage and provide excitation. Thus the voltage will build up in a regenerating direction until it exceeds that of a double unit of the battery whereupon charging current will flow in the battery, producing regenerative braking.

Such current will of course flow through one or more of the series windings 51 to 53 of the motor and produce excitation in opposition to that of the braking shunt winding 70 so as to prevent further rise of voltage and arrive at a state of equilibrium.

The braking shunt winding 70 is shunted by a diode 72 and connected in series with a resistor 73 shown as shunted by a braking current controller 74. This can be actuated to provide additional braking. Alternatively, the resistor may be variable, for example it may be a carbon pile resistor, or there may be a number of contactors serving to short circuit portions of the resistor progressively. A further resistor (not shown) may be connected between the regenerating contacts 63 to provide dynamic (but not regenerative) braking to standstill.

When the vehicle is coasting at high speed there is no tendency for a pure series machine to regenerate. Operation of the brake initiation contactor allows the residual field to build up the excitation in the shunt field till the generated e.m.f. exceeds the double unit battery voltage plus the drop in two diodes. Short circuiting the resistor 73 in series with the shunt field will increase the excitation and hence the regenerative current. An advantage of regenerative braking is that it stabilizes the mechanical drive train by damping out torsional oscillation.

A further pair of change-over contacts 80 are provided disconnecting one terminal of the battery from the load circuit, and connecting it to the output terminals 81 of a charger for charging the battery. The change-over contacts of the battery system will of course be in the position giving the full voltage when charging.

The arrangement of Figure 2 may be provided with an auxiliary supply circuit as in Figure 1.

In a known system it has been proposed to provide each of a number of single battery units with a change-over contact set comprising a common contact capable of connection to either of a pair of individual contacts connected to opposite terminals of the unit. In this case one individual contact of one unit was directly connected to the common contact of a neighbouring unit, whereas in the present invention one individual contact of a single unit is connected to an individual contact of the other single unit of the same double unit, while the common contact is connected to the common contact of a neighbouring double unit.

This has advantages not connected with auxiliary supplies, for example that only three main powerleads, instead of four, are needed for two units, and the middle lead, which is only conducting when one single unit is in circuit and the other is not, can usually be of smaller capacity.

The invention is however particularly valuable in connection with auxiliary supplies and/or certain arrangements for regenerative braking in that each pair of single units is permanently connected in series, enabling a unit of double the voltage to be available at all times.

As compared with an arrangement in which the auxiliary load is only supplied by one single unit at a time, the arrangement has the advantage, first, that the auxiliary load power is shared between two single units and the current taken from each is half what would otherwise be required. In addition it only requires half the number of double pole on/off contactors which must be fairly heavy, particularly if the whole of the auxiliary power is taken from a single battery unit. In addition to halving the number of contactors it also halves the current rating of each contactor. Moreover when a pair of battery units is in circuit, battery current is carried only by cables at the terminals of the pair of units instead of being carried by cables at the terminals of each unit. The double battery unit requires only three connections instead of four.

Similarly if the battery is to be exchanged the number of battery disconnecting points is reduced.

WHAT WE CLAIM IS: 1. A multi-cell electric battery system for supplying a main load at any one of a number of sub-divisions of the full battery voltage, in which the battery is divided into a number of double battery units each comprising two single battery units permanently connected in series and which includes, for each single unit, a set of change-over contacts comprising a common contact and what will be termed inner and outer contacts connected respectively to opposite terminals of the single unit, the inner contacts of a double unit being connected together and to the junction of the positive terminal of one single battery unit and the negative terminal of the other, and the common contacts forming terminals of the double units and being connected in series across the main load terminals so as to supply the main load with different voltages corresponding to the voltages of different combinations of single units in series.

2. A system as claimed in Claim 1 for also supplying auxiliary load terminals at a predetermined sub-division of the full battery voltage, including double-pole contacts arranged to connect the auxiliary load terminals selectively to the terminals of each double battery unit, to supply the auxiliary load at twice the voltage of a single unit.

3. A system as claimed in Claim 1 or Claim 2 for supplying a motor including a motor current conducting diode connected between the common contact and inner contact of each single unit so that, while the change-over contact is changing over, current from the other units through the motor can flow through the motor current conducting diode.

4. A system as claimed in any one of the preceding claims providing regenerative braking, including a regeneration current conducting diode connected between the common contact and outer contact of each single unit so that while the contact is changing over, a reverse regenerative braking current can continue to flow through the regeneration current conducting diode.

5. A system as claimed in Claim 4 in which each of the regeneration current conducting diodes is connected in series with a resistor or inductor.

6. A system as claimed in Claim 5 in which each of the regeneration current conducting diodes is a zener diode.

7. A system as claimed in any one of Claims 1-3 providing regenerative braking in which the terminals of the load circuit are connected to the terminals of the battery through regeneration change-over contacts serving to disconnect them from the common contacts of the end battery units and connect them to all the double units in parallel through diodes permitting current to flow in each double unit only In a charging direction.

8. A system as claimed in any one of the preceding claims including a load circuit comprising a series wound motor having an armature and series field and a braking shunt field winding connected through a brake initiation contactor across the motor armature in opposition to the series winding.

9. A system as claimed in Claim 8 including a resistor in series with the braking field winding and means for short circuiting and/or varying the effective value of such resistor to vary the braking.

10. A system as claimed in any one of Claims 7 to 9 including a resistor connected across the double units in parallel, together with their diodes.

I I. A multicell electric battery system as specifically described herein with reference to Figure 1 or Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. terminals of each unit. The double battery unit requires only three connections instead of four. Similarly if the battery is to be exchanged the number of battery disconnecting points is reduced. WHAT WE CLAIM IS:

1. A multi-cell electric battery system for supplying a main load at any one of a number of sub-divisions of the full battery voltage, in which the battery is divided into a number of double battery units each comprising two single battery units permanently connected in series and which includes, for each single unit, a set of change-over contacts comprising a common contact and what will be termed inner and outer contacts connected respectively to opposite terminals of the single unit, the inner contacts of a double unit being connected together and to the junction of the positive terminal of one single battery unit and the negative terminal of the other, and the common contacts forming terminals of the double units and being connected in series across the main load terminals so as to supply the main load with different voltages corresponding to the voltages of different combinations of single units in series.