Determining state of charge of battery connected to charger involves forming ratio of battery voltage and load current differences for two different charger output voltages at same temperature

摘要

The method involves determining the battery internal impedance from measurement parameters and comparing with a stored characteristic to determine the charge state. The demanded battery current is reduced charger and output voltage demand value is reduced to cause a low discharge current to flow. The discharge current and battery voltage values are stored, the charger output voltage is reduced further and the new load current and battery voltage stored immediately afterwards and at the same temperature. The internal impedance is derived from the ratio of voltage and current differences.