Battery residual charge indicator for battery packs has a test circuit integrated in battery case

摘要

When battery (14) is inserted in battery case (10), its terminals (24) briefly contact test terminals (27) connected to a measurement circuit and a load resistor (43). The test circuit monitors the voltage across the resistor as an indication of the state of charge. A green light emitting diode (LED) (46) indicates that battery charge is adequate and a red LED (52) shows that it is inadequate.