Abstract: A monitor for disabling a selected operative function of the battery powered vehicle when the battery reaches a predetermined discharge state is disclosed. The discharge state of the battery is determined by continuously monitoring the terminal voltage of the battery. Automatic scaling circuitry is included so that the monitor automatically adjusts to the range which is appropriate for the battery being monitored. Two warning signals are generated with each warning signal indicating a progressively lower discharge state of the battery. After the second warning signal has been on for a predetermined time period, a selected operative function of the vehicle is disabled. If the vehicle is a fork-lift truck for example, the lift mechanism might be disabled however the main drive motor could remain operative so that the truck could be returned to the battery charging station. The monitor also prohibits the disabled function from being reenergized except when a fully charged battery is installed in the vehicle.