Internal battery temperature estimation using series battery resistance measurements during cold temperatures

A technique has been developed to estimate the internal battery temperature (Tbat) of secondary batteries by measuring the series battery resistance (RB) at cold ambient temperatures. Tests were performed on both lead-acid and nickel metal hydride batteries at different cold temperatures to obtain useful plots of RB versus Tbat. RB was measured by using a pulse discharge circuit to apply a short-duration current pulse (IB) directly to the battery. The test results indicated that RB not only varies with temperature but also varies with the amplitude of IB. The RB versus Tbat plots were later utilized to predict Tbat from RB during alternating current (AC) battery heating at cold ambient temperatures.