Patent ID: 8749193

Claim:
A protection circuit for controlling the charge and discharge of an auxiliary battery of a multi-battery power supply and charging system, the multi-battery power supply and charging system including a chassis storage battery for supplying electrical power to chassis loads, the auxiliary storage battery for supplying electrical power to auxiliary loads, and an electrical power generator for charging the batteries and supplying electrical power to the loads, the electrical power generator, the batteries and the loads each having an ungrounded terminal and each having a grounded terminal connected to a common ground, the ungrounded electrical power generator terminal being connected to the ungrounded chassis battery terminal, the protection circuit comprising: (a) circuit node connection terminals including an electrical power generator node for connection to the ungrounded terminal of the electrical power generator, an auxiliary battery node for connection to the ungrounded terminal of the auxiliary storage battery, an auxiliary load node for connection to the ungrounded terminal of the auxiliary load and a ground node for connection to the common ground; (b) a switching control circuit including a digital processor, the control circuit having a voltage sensing circuit connected to the power generator node, a voltage sensing circuit connected to the auxiliary battery node, a ground terminal for connection to the common ground and outputs for controlling switches; (c) an electrically controlled first switch connected between the power generator node and the auxiliary load node, the first switch having a control input terminal connected to an output of the control circuit for being switched between a closed state and an open state by the control circuit; (d) an electrically controlled second switch connected between the auxiliary load node and the auxiliary battery node, the second switch having a control input terminal connected to an output of the control circuit for being switched between a closed state and an open state by the control circuit.