Measurement of the state of battery charge using an improved loaded voltmeter test method

An improved loaded voltmeter test (ILVT) was developed based on the preparation of a table of voltage measurements of the tested battery with a constant resistor load as a function of the state of charge. The function is stored in the memory of the microcomputer; when a certain value of the charge is then needed, it can be found using the ILVT and the stored function. The action of the power system is not disturbed. A circuit based on this method was built and tested at Tel Aviv University, Israel. Half as many errors occurred when the ILVT was used as when the conventional loaded voltmeter test was used. Although the system consists of only lead-acid batteries, the ILVT is also suitable for testing other types of batteries.