US Patent 6888468 Apparatus and method for protecting a battery from overdischarge

A battery discharge indicator for protecting a storage battery is provided. The battery discharge indicator includes a positive connector that can couple to a positive terminal of the battery and a negative connector that can couple to a negative terminal of the battery. Also included, is a voltage sensor that couples to the battery via the positive connector and the negative connector and senses a battery terminal voltage. A microprocessor, coupled to the voltage sensor, provides a first alarm signal if a magnitude of the battery terminal voltage is below a first threshold for a first interval of time and if the magnitude of the battery terminal voltage is below a second threshold for a second interval of time.