US Patent 7786698 Charging a secondary battery

A method of charging a battery includes applying a charging current from a semiconductor device to the battery during a first battery charging time period. The method also includes measuring a charging voltage level at the battery during the first battery charging time period. During a non-charging voltage measurement time interval, the method includes temporarily stopping application of the charging current from the semiconductor device to the battery and measuring a non-charging voltage level at the battery while the charging current is not being applied to the battery.