Battery stress relief system with bypass

A power pack assembly, the power pack assembly comprising:

• a housing configured to store a battery;
• and
• a power system supported by the housing, the power system comprising:
• a battery charge path that extends between a portion of the housing and a terminal supported by the housing;
• a first thermistor arranged along the battery charge path and having a resistance that decreases with an increase in a first temperature to a first threshold temperature range;
• a bypass path arranged in parallel to the battery charge path and having a switch element configured to selectively restrict current flow and permit current flow along the bypass path;
• and
• a switch circuit comprising:
• a second thermistor having a resistance that increases responsive to an increase in a second temperature to a second threshold temperature range;
• and
• a resistor configured to vary voltage supplied to the switch element to effectuate a transition of the switch element;
• wherein, responsive to the second temperature being below the second threshold temperature range, the switch circuit is configured to prevent current flow along the bypass path at the same time the first thermistor is defined by a high resistance that substantially restricts current flow between the battery and a load;
• and
• wherein, responsive to the second temperature exceeding the second threshold temperature range, the switch circuit is configured to allow current flow along the bypass path at the same time the first thermistor is defined by a low resistance that allows current to flow between the battery and the load.

A method for charging a load, comprising:

• causing current from a battery to flow through a first thermistor located along a battery charge path, the battery charge path coupling the battery to a load;
• and
• operating a switch circuit to cause a switch element to allow current to flow between the battery and the load along a bypass path that is arranged in parallel to the battery charge path, wherein operating the switch circuit comprises varying, by a resistor, a voltage supplied to the switch element responsive to a change in resistance of a second thermistor of the switch circuit;
• wherein the change in resistance of the second thermistor is responsive to an increase in temperature of the second thermistor;
• wherein, responsive to the temperature being below a threshold temperature range, the switch circuit is configured to prevent current flow along the bypass path at the same time the first thermistor is defined by a high resistance that substantially restricts current flow between the battery and load;
• and
• wherein, responsive to the temperature exceeding the threshold temperature range, the switch circuit operates the switch element to allow current flow between the battery and the load along the bypass path at the same time that current from the battery is caused to flow to the battery along the battery charge path.