System for supplying electrical power to start vehicle engines

A protection circuit for protecting an energy storage device, wherein the current protection circuit comprises:

• a first circuit region electrically coupled to a first terminal of the energy storage device, the first circuit region comprising a first connector node;
• a second circuit region electrically coupled to a second terminal of the energy storage device, the second circuit region comprising a second connector node;
• a latching circuit to electrically couple the first connector node to the first terminal of the energy storage device when the latching circuit is in a closed configuration and electrically decouple the first connector node from the first terminal of the energy storage device when the latching circuit is in an open configuration, the latching circuit remaining in the closed configuration if no voltage is supplied to an operational switch of the latching circuit;
• and
• a contactor circuit electrically coupled to the operational switch of the latching circuit, the contactor circuit comprising a microcontroller and a capacitor electrically coupled to the first circuit region, wherein the capacitor is configured to store power collected from the first circuit region and the microcontroller is configured to monitor a current or a voltage from the energy storage device and, if the current is above a current threshold value or the voltage is below a voltage threshold value, cause the capacitor to discharge to the operational switch of the latching circuit to cause the latching circuit to transition to the open configuration;
• wherein the battery is a lithium-metal battery or a nickel-metal hydride battery.