A New “Fuel” Gage for Electrically Powered Vehicles

New techniques, using a special capacitive readout version of the Curtis mercury coulometer, are being used in an ampere-hour meter for rechargeable battery systems. The circuit meets one definition of the “perfect fuel” gage for battery powered vehicles. The unit consists of a small solid-state electronics module driving an indicating meter. It is powered from the battery and will directly and automatically indicate ampere-hours discharged and charged. The unit has an automatic stop when the meter displays “full” or 100% of capacity to permit a safe overcharge situation. Additionally, the unit can provide alarms and detectors for low capacity signals or auxiliary charge control functions. The system is currently under test on a number of battery-powered vehicle programs.