US Patent 8129999 Dielectric breakdown detector for HEV battery application

A circuit that indicates an impedance of a battery dielectric includes a signal generator module that flows a first current from a ground to a first terminal of a battery. A sensor circuit generates a signal based on a second current that flows from a second terminal of the battery through a resistance to ground. The second current includes the first current and a third current that flows to ground via an impedance presented by a battery dielectric housing. A signal conversion module generates an output signal based on the signal. The output signal represents the impedance presented by the battery dielectric housing.