The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes of operation are possible: When the propulsion power pack voltage is above the 63-V trip point, the electronic switch has no effect on operation.
When the propulsion power pack no load voltage is below 63 V, power will not be supplied to the propulsion motor since the electronic switch will prevent contactor operation. When the propulsion power pack loaded voltage drops below 63 V, the contactor will close and npen because of the electronic switch. The bucking operation indicates to the operator need to charge the batteries.