Vehicle battery discharge indicator

Claim 3

A method as claimed in Claim 1 in which step b is performed by storing as a reference voltage value the lesser of the first voltage and a predetermined voltage value representing the maximum open-circuit emf of the storage battery (16) without a surface charge.

Claim 4

A method as claimed in Claim 1 or Claim 2 in which steps c and d are performed at predetermined first timed intervals and step e is performed after the occurrence of a predetermined number of consecutive first timed intervals for which the second voltage is less than the reference voltage value.

Claim 5

A method as claimed in Claim 3 in which step e is performed during a predetermined second timed interval less than the first timed intervals, whereby step e may be initiated after each comparing step and terminated prior to the next comparing step.

Claim 6

A battery discharge indicator for a storage battery (16) of a motor vehicle powered by an internal combustion engine (22), the vehicle including a unidirectional current source (12) connected to the parallel combination of the storage battery and an electrical load (18), the storage battery having an open-circuit emf, the unidirectional current source normally supplying current to the storage battery and the electrical load to impress upon the storage battery a circuit voltage greater than the open-circuit emf of the storage battery for charging the storage battery, the battery discharging when the circuit voltage impressed upon the storage battery is less than the open-circuit emf of the storage battery, the battery discharge indicator being characterised by first measuring means (38) for measuring a first voltage of the storage battery before cranking the engine each time the engine is started; storing means (38) for storing the first voltage as a reference voltage value; second measuring means (42) for measuring a second voltage of the storage battery after the engine is started; comparing means (54) for comparing the second voltage with the stored reference voltage value; and indicating means (62) for indicating that the storage battery is discharging when the second voltage is less than the reference voltage value.

Claim 7

A battery discharge indicator for a storage battery (16) of a motor vehicle powered by an internal combustion engine (22), the vehicle including a unidirectional current source (12) connected to the parallel combination of the storage battery and an electrical load (18), the storage battery having an open-circuit emf, the unidirectional current source normally supplying current to the storage battery and the electrical load to impress upon the storage battery a circuit voltage greater than the open-circuit emf of the storage battery for charging the storage battery, the battery discharging when the circuit voltage impressed upon the storage battery is less than the open-circuit emf of the storage battery, the battery discharge indicator being characterised by first measuring means (38) for measuring a first voltage of the storage battery before cranking the engine each time the engine is started; storing means (38) for storing the first voltage as a reference voltage value; second measuring means (42) for measuring a second voltage of the storage battery after the engine is started; comparing means (54) for comparing the second voltage with the stored reference voltage value; and indicating means (62) for indicating that the storage battery is discharging when the second voltage is less than the reference voltage value.

Claim 8

A battery discharge indicator as claimed in Claim 5 in which the motor vehicle includes a voltage regulator (14), for determining the circuit voltage level, and an ignition switch operable to a run position and then to a crank position at which current is supplied from the storage battery (16) to a cranking motor for starting the engine (22), and in which the storage battery (16) has an open-circuit emf dependent upon battery conditions, wherein the first measuring means (38) measures the first voltage after the ignition switch is operated to the run position and before being operated to the crank position so that the first voltage is measured before current is supplied from the storage battery to the cranking motor; the reference voltage value represents the open-circuit emf of the storage battery compensated for the battery conditions existing when the first voltage is measured; the second measuring means (42) measures the second voltage of the storage battery at predetermined first timed intervals; the comparing means (54) compares the second voltage with the stored reference voltage value at each of the predetermined first timed intervals; and the indicating means (62) indicates that the storage battery is discharging after the occurrence of a predetermined number of consecutive first timed intervals for which the second voltage is less than the reference voltage value, and is operative for a predetermined second timed interval less than the first timed interval, whereby the indicating means may be initiated each of the first timed intervals and terminated prior to the next first timed interval.