Improvement of intelligent battery controller: state-of-charge indicator and associated functions

A few hundred electric vehicles have been field tested by ‘Electricité de France’ for several years. Most of them are equipped with valve-regulated lead/acid batteries. It is well known that the battery is the weak element of electric vehicles. Analysis of operation problems during field tests and laboratory investigations has led to the consideration that this situation could be improved by the use of an efficient battery-management system. An on-board management device has been developed with the Intelligent Electronic Systems company. Commercialized under the name Intelligent Battery Controller (IBC), its main features are: rapid and normal charge monitoring, data recording, state-of-charge indication and help for maintenance. First prototypes produced up to now have no state-of-charge indication. The battery management during driving was limited to the indication of charge/discharge Ah, and orange and red alarms related to deep depth-of-discharge. The upgraded version presented here is mainly characterized by a state-of-charge indicator that is corrected for temperature, rate of discharge, and ageing of the battery.