This invention relates to switching apparatus. This invention has particular but not exclusive application to automotive electrical systems, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as stationary battery-powered equipment.

Modern motor vehicles contain many accessories which are operated by the vehicle electrical system. When the engine is running, these accessories are powered by the engine- driven alternator. When the vehicle is stationary, some accessories such as lights, fans and audio systems may still be operable, drawing power from the vehicle battery. On occasions, the power drawn from the battery while the engine is not operating may discharge it to the extent that it cannot start the engine. If this occurs, the vehicle must be push or jump-started before the battery can be recharged by the alternator, and this can be very inconvenient. The present invention aims to alleviate the above disadvantage and to provide switching apparatus which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in one aspect resides broadly in switching apparatus for regulating the output from an energy storage apparatus, including:- regulating apparatus for regulating the output from said energy storage apparatus; monitoring apparatus for monitoring a measure of the state of charge of said energy storage apparatus, and control means responsive to said monitoring apparatus for controlling said regulating apparatus for selectively

switching said output according to said state of charge.

Preferably, the energy storage apparatus is an electric accumulator _r and the monitoring apparatus includes switching means for disconnecting selected electrical loads from said electric accumulator. Of course other energy storage apparatus such as hydraulic or pneumatic accumulators may be used if desired.

The measure of the state of charge of the electric accumulator may be the output voltage of the electric accumulator, and the monitoring apparatus includes control means for operating said switching means for disconnecting selected electrical loads from said electric accumulator when its voltage falls below a pre-set value. In an automotive application, the pre-set value may be the minimum value for reliable starting performance. Of course, if desired, other measures of the state of charge may be used, such as the density of electrolyte within the electric accumulator.

The regulating apparatus may be formed for complete interruption of the flow of power from the energy storage apparatus, and an override switch may be provided for controlling the reconnection of power to selected loads as desired. The override switch may be formed integral with the switching apparatus, or it may be mounted remotely therefrom in a selected position such that it may be operated more conveniently. Alternatively, the regulating apparatus may be formed for interrupting the power to selected loads, such as non-essential loads including sound systems, while maintaining power flow to other selected loads such as essential loads including starter motors and ignition systems.

The regulating apparatus may be formed to interrupt the flow of power when the state of charge of the electrical accumulator reaches a selected level, and to resume the flow of power when the state of charge reaches a further and higher level. It is preferred however that the regulating

apparatus be formed to interrupt the flow of power until the override switch is operated, such that an operator may be made aware of the operation of the switching apparatus. Override alarm means, such as a warning light, may be associated with the override switch for indicating operative use thereof whereby a user may be made aware that the switching apparatus is not functional.

In a further aspect of this invention, security apparatus is disclosed for selectively regulating the use of an energy storage apparatus, said security apparatus including:- regulating apparatus for regulating the flow of output power from the energy storage apparatus; and security control means for selectively controlling said regulating apparatus in response to a pre-programmed operator input.

Preferably, the energy storage apparatus includes an electric accumulator, and said regulating apparatus includes switching means for disconnecting selected electrical loads from the electric accumulator. Of course other energy storage apparatus such as hydraulic or pneumatic accumulators may be used if desired.

The security switching means may include a keylock or a combination lock, but it is preferred that it include a data- entry keypad for accepting codes or numbers, and decoding means for operating the regulating apparatus in response to the entry to the keyboard of a pre-programmed code or combination of numbers. The security apparatus may include a security enclosure disposed about the electric accumulator and/or the decoding means, and the security enclosure may include locking means for selectively unlocking an access panel thereto such that access to the security enclosure for unauthorized bypassing of the security apparatus is minimised. The locking means

may include a latch biased into operative locking engagement between the security enclosure and the access panel by biasing means such as a spring, the latch being releasable by an electric actuator such as a solenoid in response to a preprogrammed code or number entered at the keypad. In an automotive application, for instance, the security enclosure may be the engine compartment or the boot, and the access panel may be the hood, bonnet or boot lid.

The security apparatus may include emergency latch release means, which may include an auxiliary power connector disposed external to the security enclosure and connected to the keypad and the decoding means such that, in the event of failure of the electric accumulator, the locking means may be released by energising the keypad and the decoding means by a standby battery attached to the auxiliary power connecter and entering a pre-determined code to the keypad. The standby battery may be permanently connected to the latter, or attachable thereto as necessary.

In another aspect, this invention resides in combined switching and security apparatus for use in conjunction with an energy storage apparatus, including:- regulating apparatus for regulating the flow of output power from said energy storage apparatus; monitoring apparatus for monitoring a measure of the state of charge of said energy storage apparatus; control means responsive to the output from said monitoring apparatus for controlling said regulating apparatus for switching said output when said state of charge reaches a selected level; and security switching means for selectively regulating said regulating apparatus in response to a pre-programmed operator input.

Preferably, the energy storage apparatus is applied to a vehicle, and includes an electric accumulator, the regulating

apparatus includes electrical switching means, the monitoring apparatus includes voltage measurement means for monitoring the output voltage of said electric accumulator, and the security switching means includes a data-entry keypad for accepting codes or numbers and decoding means for operating said regulating apparatus in response to the entry to the keypad of a pre-programmed code or combination of numbers.

The regulating apparatus may include a single relay disposed between the electric accumulator and all or selected ones of the loads applied thereto. Suitably, the regulating apparatus includes a security relay associated with loads essential to the operation of the vehicle and operable by the security switching means, and a discharge-prevention relay associated with non-essential loads which may be utilised independently of vehicle operation such as lights and audio equipment and operable by the monitoring apparatus. This embodiment enables non-essential loads to be utilizable by a user while retaining the facility to protect the vehicle from unauthorized use and uncontrolled battery discharge. In a further aspect of this invention, a method of controlling the output of an electric accumulator is disclosed, including:- providing switching apparatus for controlling the flow of output power from said electric accumulator to selected electrical loads; providing voltage measurement and control apparatus for monitoring the output voltage of said electric accumulator and controlling said switching apparatus for selectively disconnecting said selected electrical loads from said electric accumulator; connecting said switching means to the electric accumulator; and operating said measurement and control apparatus and said switching apparatus such that said selected electrical

loads are operatively disconnected from said electric accumulator when its output voltage falls below a preset value.

In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:-

FIG. 1 is a circuit diagram of a switching apparatus for a motor vehicle, and FIG. 2 is a circuit diagram of a switching apparatus for a motor vehicle which includes a security apparatus. The switching apparatus 10 shown in FIG. 1 includes a relay assembly 11 comprising a relay coil 12 and a relay contact 13. The relay coil 12 is driven by a monitoring assembly 14. Within the latter is a comparator 15, the output of which is connected to a current amplifier 16, the latter driving the relay coil 12.

The inverting input 17 of the comparator 15 is connected to the positive power rail 20 and the negative power rail 21 through a resistive divider assembly 22 comprising an upper resistor 23 and a lower resistor 24, such that the inverting input 17 is held at a selected fraction of the voltage between the positive power rail 20 and the negative power rail 21. The non-inverting input 25 of the comparator 15 is connected to the positive power rail 20 by a third resistor

26, and to the negative power rail 21 by a voltage reference

27, such that the non-inverting input 25 is held at a constant voltage relative to the negative power rail 21. The negative power rail 21 is connected directly to the negative terminals of a battery 28 and accessories 30 and 31. The positive power rail is connected directly to the positive terminals of the accessories 30 and 31, and to the positive terminal of the battery 28 through the relay contact 13. A manual override switch 32 is connected between the

positive terminal of the battery 28 and the active terminal of the relay coil 12.

For as long as the fraction of the battery voltage sensed by the resistive divider assembly 22 and appearing at the inverting input 17 is greater than the fixed voltage held at the non-inverting input 25 by the voltage reference 27, the output of the comparator will remain high, energising the relay coil 12 and holding the relay contact 13 closed such that the accessories 30 and 31 may be energised. If the accessories 30 and 31 draw current while the battery 28 is not being charged and the battery voltage drops to a pre-determined level, the voltage appearing at the inverting input 17 will fall below the constant voltage on the non-inverting input 25, sending the output of the comparator 15 low and de-energising the relay coil 12. This opens the relay contact 13, disconnecting the accessories 30 and 31 from the battery 28 and preserving its remaining charge for starting the vehicle.

The monitoring assembly 14 is also disconnected from the battery 28 by the opening of the relay contact 13 such that any momentary increase in battery voltage due to a reduction in loading does not cause the comparator output to be sent high again, as this would allow the relay contact 13 to reconnect the accessories 30 and 31. The override switch 32 must be operated to reconnect the accessories 30 and 31 and the monitoring assembly 14 after the battery 28 has been charged.

The switching apparatus 40 shown in FIG. 2 is mounted in a vehicle and includes a relay assembly 41 comprising a relay coil 42 and a relay contact 43. The relay coil 42 is driven by a monitoring assembly 44. Within the latter is a comparator 45, the output of which is connected to a current amplifier 46, the latter driving the relay coil 42.

The inverting input 47 of the comparator 45 is connected to the positive power rail 50 and the negative power rail 51

through a resistive divider assembly 52 comprising an upper resistor 53 and a lower resistor 54, such that the inverting input 47 is held at a selected fraction of the voltage between the positive power rail 50 and the negative power rail 51.

The non-inverting input 55 of the comparator 45 is connected to the positive power rail 50 by a third resistor

56, and to the negative power rail 51 by a voltage reference

57, such that the non-inverting input 55 is held at a constant voltage relative to the negative power rail 51.

The negative power rail 51 is connected directly to the negative terminals of a battery 58 and accessories 60 and 61. The positive power rail is connected directly to the positive terminals of the accessories 60 and 61, and to the positive terminal of the battery 58 through the relay contact 43. A manual override switch 62 is connected between the positive terminal of the battery 58 and the active terminal of the relay coil 42.

A keypad 63 is attached to the dashboard of the vehicle, and is connected to a decoder 64 mounted within the engine compartment of the vehicle. Outputs from the decoder 64 are connected to a security relay coil 65 and a solenoid 66 connected to a latch 67 which is arranged to open the bonnet 70 of the vehicle when the solenoid 66 is energised. A solenoid spring 71 holds the latch 67 in a position engaged with the bonnet 70 when the solenoid 66 is not energised. The security relay coil 65 controls a security contact 72 through which the battery 58 is connected to the ignition system 73. A pair of auxiliary battery terminals 74 and 75 are associated with the keypad 63 and are arranged to supply power from an auxiliary battery connected thereto to the decoder 64.

If accessories 60 or 61 are left in an energised state when the vehicle is not operating and the battery 58 becomes

discharged to an undesirable state, the switching apparatus 40 functions in a similar manner to the switching apparatus 10 shown in FIG. 1. When the vehicle is not in use, the security relay coil 65 is not energised, and the security contact 72 remains open, leaving the ignition system 73 disabled. The solenoid 66 is also unenergized, leaving the latch 67 to be urged into locking engagement with the bonnet 70.

When a user wishes to operate the vehicle, he must enter through the keypad 63 a code number which the decoder 64 is pre-programmed to recognise. On receipt of such a code number, the decoder 64 energises the solenoid 66, permitting the bonnet 70 to be opened for access to the engine compartment and also energises the security relay coil 65, permitting the engine to be started.

If the battery 58 becomes discharged to a state such that it cannot energise the solenoid 66, the bonnet 70 may be unlocked by connecting an auxiliary battery to the terminals 74 and 75 to energise the decoder 64 and entering a valid code number code at the keypad 63.

A user not in possession of a valid code number will be unable to energise the ignition system 73 through the decoder 64 and the security contact 72. In addition, such a user cannot obtain access to the decoder 64 or the security relay 65 to bypass them as the latch 67 will hold the bonnet 70 in a locked position until the solenoid 66 is energised by the decoder 64.

It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is defined in the appended claims.