Battery state of charge evaluator system

A battery state of charge evaluator comprising:

• means responsive to the battery current for producing a current value,
• means for integrating the current value with respect to time to obtain a value respresenting charge withdrawn,
• means responsive to the battery voltage for producing a voltage value,
• means for determining the state of charge, said means determining the state of charge from the charge withdrawn value and a value representing charge storage capacity during a first part of each discharge and determining the state of charge from the voltage value during a last part of each discharge, and
• means for correcting the battery charge storage capacity value in accordance with the state of charge as determined from the battery voltage and the charge withdrawn value.

A state of charge evaluator system comprising an electric vehicle traction battery and a battery state of charge evaluator which are arranged to be detachable from the vehicle as a single unit, said evaluator comprising:

• means responsive to battery current for producing a current value,
• means for integrating the current value with respect to time to obtain a value representing charge withdrawn,
• means responsive to battery voltage for producing a voltage value,
• means for determining the state of charge, said means determining the state of charge from a charge withdrawn value and a value representing the charge storage capacity during a first part of each discharge and determining the state of charge from the voltage value during a last part of each discharge, and
• means for correcting the battery charge storage capacity value in accordance with the state of charge as determined from the battery voltage and the charge withdrawn value.