GB2205697A

GB2205697A - Automotive electric storage battery power system

Info

Publication number: GB2205697A
Application number: GB08713663A
Authority: GB
Inventors: Allan George Alexander Guthrie
Original assignee: Chloride Group Ltd
Current assignee: Chloride Group Ltd
Priority date: 1987-06-11
Filing date: 1987-06-11
Publication date: 1988-12-14
Also published as: GB8713663D0

Abstract

An automotive electric storage battery 2 of secondary type in situ in a motor vehicle is connected to the electric components 4 of the vehicle and connected in parallel with a primary battery 6 of higher voltage (e.g. 18 volts) with the interposition of an electric resistance 12 and a diode 10 which prevents current flowing from the electrical components of the vehicle, e.g. the alternator, through the primary battery. The state of charge of the secondary battery 2 is substantially maintained for an extended period of time because, when the vehicle engine is not running, the primary battery 6 supplies a substantial portion (e.g. initially 90 per cent or more) of the residual electrical demand of components which are partly or wholly energised at all times, such as a clock and a computer. The arrangement is of particular use when a vehicle is exported, since the secondary battery 2 will still be able to start the engine on arrival at the destination, whereat the primary battery 6 may be discarded. The battery 6 may be coupled to battery 2 via the cigarette lighter socket in the vehicle. <IMAGE>

Description

AUTOMOTIVE ELECTRIC STORAGE BATTERIES The present invention relates to automative electric storage batteries and is concerned with maintaining such batteries in a good condition, that is to say in an acceptable state of charge, for a prolonged period of time in which the vehicle engine is not started, i.e. a period during which the battery is not recharged.

Automotive batteries, which are also known as starting lighting and ignition batteries, are provided in motor vehicles to provide a substantial amount of power for short periods in order to actuate the vehicle engine starter motor and to provide smaller amounts of power to energise various electrical equipment, such as lights, the ignition circuit, a radio and the like during those periods when the engine is not running or the vehicle alternator or generator is producing insufficient power to satisfy all the vehicles electrical requirements. When the engine speed is sufficient the battery is recharged by the alternator or generator.

When the vehicle engine is not running the battery is subject to two separate types of degradation of its state of charge. The first of these is the inevitable self-discharge to which all secondary batteries are prone and the second is due to the small drain current which the battery inevitably always supplies through leakage paths in the vehicle electrical system and to power electrical devices such as clocks and the like which are permanently connected to the battery and operative.

When a motor vehicle is exported or stored for a prolonged period during the distribution process it is desirable, and indeed a requirement, that its battery be fitted so that the engine can be started and the vehicle moved under its own power both during and at the end of a transport process. When vehicles are exported to remote destinations, such as Australia, the battery may remain in situ in the car for several months without receiving a top-up charge. During this period its state of charge gradually decays for the reasons explained above and it is found that when the vehicle arrives at its destination the state of charge of the battery has frequently decayed to such an extent that it is incapable of starting the vehicle engine and is incapable of subsequently operating effectively and must thus be replaced by a new battery.This problem is becoming increasingly severe as motor vehicles are now being provided with increasing amounts of electrical equipment such as computers, central locking systems and electronic memory circuits which are partially or fully energised at all times and it is found that the residual drain current required to power such equipment in a sophisticated motor car is typically as high as 30mA.

It is therefore an object of the present invention to provide a method of maintaining automotive batteries in a good condition for an extended period of time without providing a top-up charge for the vehicle electrical system so that the problems referred to above are substantially avoided and so that, in particular, the vehicle may be exported to a remote destination and its engine may still be started by its automotive battery and the battery does not need to be replaced by a new one on arrival.

According to the present invention there is provided an automative electrical storage battery in situ in a motor vehicle connected to the electrical components of the vehicle and connected in parallel with a further battery of higher voltage with the interposition of an electrical resistance.

Thus in the present invention a further battery, which may be a further secondary battery but is preferably a primary battery, of higher voltage than the automotive battery is provided which satisfies a substantial proportion of the residual load requirement of the electrical components of the vehicle. This is ensured by virtue of the fact that the further battery is of higher voltage and the power which is supplied to the various operative components, such as the on-board computer system, is maintained at the correct level by virtue of the provision of the electrical resistance.

This resistance will in general be more than 10 or 50 Ohms and is typically about 60 Ohms. The voltage and capacity of the further battery are selected in accordance with the residual electrical load requirement of the vehicle and the anticipated length of time for which the automotive battery is to be maintained in a good condition. Typically, however, the further battery will have a voltage 30% or more, e.g. 50%, greater than that of the automotive battery.

It is preferred that the further battery initially supplies a substantial portion, e.g. 90% or more, of the residual load requirement but this proportion is in practice likely to fall progressively as the primary battery becomes discharged and ideally the further battery is so dimensioned that it is substantially discharged at the end of the anticipated length of the period for which the automotive battery is to be maintained in a good condition.

If the further battery is a primary battery it is desirable to protect this battery from the reverse voltage which would be applied to it by the generator or alternator of the vehicle when the vehicle engine is started and for this purpose there is preferably a diode between the automotive battery and the further battery arranged to prevent current flowing from the electrical components of the vehicle through the primary battery.

The invention also embraces a motor vehicle including an automotive battery and a further battery as referred to above. The further battery may be placed adjacent to the automotive battery and connected to it, e.g. by trailing connectors, but it is preferred that the vehicle is of the type which includes an electrical socket, e.g. a power outlet socket connected to the automotive battery and that the further battery, the electrical resistance and the diode, if present, are connected to a connector compatible with the socket and removably positioned within it thereby electrically connecting the two batteries in parallel.The electrical socket may constitute the cigarette lighter socket which is commonly provided in motor vehicles and this opens up the possibility of providing the further battery and the associated electrical components in a single package with a trailing connector which may be simply plugged into the cigarette lighter socket to connect the two batteries in parallel.

According to a further aspect of the present invention a method of substantially maintaining the state of charge of an automotive electric storage battery in situ in a motor vehicle and connected to the electrical components of the vehicle comprises connecting a further battery of higher voltage than the automotive battery in parallel with the automotive battery with the interposition of an electrical resistance and permitting a substantial proportion of the residual electrical load requirements of the said electrical components to be supplied by the further battery.

Further features and details. of the invention will be apparent from the following description of one specific embodiment which is given by way of example with reference to the single accompanying drawing which is a circuit diagram of an automotive battery and a primary battery in situ in a motor vehicle and connected in parallel.

The circuit illustrated in the accompanying drawing comprises a six cell 12 volt lead acid automotive battery 2 which is connected in series with the electrical components of the vehicle in the usual manner. These electrical components include the starter motor, the ignition circuit, the lighting circuits and various further components which are wholly or partly energised at all times, such as a clock, an on-board computer, a central locking system and electronic memory circuits. These various electrical components are represented diagrammatically in the drawing by a single electrical resistance 4.

Connected in parallel with the automotive battery 2 is a primary battery 6 which may be of any convenient type and in this case has twelve cells and an output voltage of 18 volts. Connected in series with the primary battery 6 is a fuse 8, a diode 10 and an electrical resistance 12, typically of about 60 Ohms. The components 6,8,10 and 12 are connected to a trailing connector, not shown, which is compatible with the cigarette lighter socket of the vehicle. When the automotive battery is fitted to the vehicle the cigarette lighter is removed from its socket and the trailing connector is inserted in its place to connect the two batteries 2 and 6 in parallel.Thereafter, the residual or quiescent electrical load of the electrical components of the vehicle is primarily satisfied by the primary battery 6 and the state of charge of the automotive battery 2 is thus substantially maintained.

It is of course still subject to the usual internal self-discharge but this represents typically only about 5mA of the total of typically 30mA total load to which the automotive battery is subjected. At the end of the desired period of time, e.g. when the vehicle has arrived at its destination, the trailing connector is removed from the cigarette lighter socket and the primary battery, which is now ideally substantially discharged, and the associated electrical components can be simply thrown away. The state of charge of the automotive battery 2 is sufficient to enable it to start the vehicle engine and it can therefore be retained in the vehicle and need not be replaced.

Claims

1. An automotive electric storage battery in situ in a motor vehicle connected to the electrical components of the vehicle and connected in parallel with a further battery of higher voltage with the interposition of an electrical resistance.

2. An automotive electric storage battery as claimed in claim 1 in which the further battery is a primary battery.

3. An automotive electric storage battery as claimed in claim 2 in which there is additionally a diode between the automotive battery and the further battery arranged to prevent current flowing from the electrical components of the vehicle through the primary battery.

4. An automotive electric storage battery as claimed in any one of the preceding claims in which the electrical resistance has a value in excess of 50 Ohms.

5. An automotive electric storage battery in situ in a motor vehicle substantially as specifically herein described with reference to the accompanying drawing.

6. A motor vehicle including an automotive electric storage battery as claimed in any one of the preceding claims.

7. A vehicle as claimed in claim 6 including a power socket connected to the automotive battery in which the further battery, the electrical resistance and the diode if present, are connected to a connector compatible with the socket and removably positioned within the socket thereby electrically connecting the two batteries in parallel.

8. A vehicle as claimed in claim 7 in which the said socket is a cigarette lighter socket.

9. A method of substantially maintaining the state of charge of an automotive electric storage battery in situ in a motor vehicle and connected to the electrical components of the vehicle, the method comprising connecting a further battery of higher voltage than the automotive battery in parallel with the automotive battery with the interposition of an electrical resistance and permitting a substantial proportion of the residual electrical load requirement of the said electrical components to be supplied by the further battery.

10. A method of substantially maintaining the state of charge of an automotive electric storage battery in situ in a motor vehicle and connected to the electrical components of the vehicle substantially as specifically herein described with reference to the accompanying drawing.