US Patent 10184988 Remote sensing of remaining battery capacity using on-battery circuitry

A method of remote sensing a charge includes charging or discharging a first capacitor of a first RC circuit and a second capacitor of a second RC circuit to a predetermined threshold voltage using a power source. When each of the capacitors reach the predetermined threshold voltage, a response signal is provided from a communications module to a handheld computing device comprising a reader system. An amount of time between the response signals is determined. The amount of time is indicative of charge information.