ELECTRIC VEHICLE BATTERY CONTACTOR SWITCH MONITORING

Contactor switches between a multi-cell battery pack and an electric vehicle load are monitored. A main microcontroller having a chassis ground is digitally isolated from positive and negative busses of the battery pack. A battery monitoring IC having a plurality of auxiliary/thermistor A/D inputs measures respective voltages of battery cells. An evaluation switch is connected to a junction between a first contactor switch and the load. The evaluation switch is activated in response to a command received from the main microprocessor. A voltage divider is coupled between the output of the evaluation switch and the negative bus to provide a divided voltage output to one of the auxiliary/thermistor A/D inputs. The battery monitoring IC transmits a digital value representative of the divided voltage output to the main microprocessor via a serial data link, and the main microprocessor determines a state of the contactor in response to the digital value.