A battery pack for a vehicle, the battery pack comprising: a) a firebox for enclosing batteries; b) an electronics compartment; c) thermal insulation surrounding the firebox and the electronics compartment; and d) heat pipes comprising: firebox heat pipes adjacent to the firebox on an evaporator end and extending to an exterior surface of the battery pack on a condenser end; and electronics compartment heat pipes extending from within the electronics compartment on an evaporator's end and extending through the thermal insulation to the exterior surface of the battery pack on a condenser end; wherein the firebox heat pipes comprise variable conductance heat pipes and the electronics compartment heat pipes comprise variable conductance heat pipes , and wherein the firebox heat pipes comprise variable conductance heat pipes comprising a first operating temperature range, and wherein the electronics compartment heat pipes comprise variable conductance heat pipes comprising a second operating temperature range; wherein the thermal insulation comprises at least one of: a) an aerogel; or b) a vacuum panel insulation; wherein the thermal insulation comprises an inner layer comprising a polyimide foam; and wherein the thermal insulation comprises an outer layer comprising a vacuum sealed aerogel insulation. a) a firebox for enclosing batteries; b) an electronics compartment; c) thermal insulation surrounding the firebox and the electronics compartment; and d) heat pipes comprising: firebox heat pipes adjacent to the firebox on an evaporator end and extending to an exterior surface of the battery pack on a condenser end; and electronics compartment heat pipes extending from within the electronics compartment on an evaporator's end and extending through the thermal insulation to the exterior surface of the battery pack on a condenser end; wherein the firebox heat pipes comprise variable conductance heat pipes and the electronics compartment heat pipes comprise variable conductance heat pipes , and wherein the firebox heat pipes comprise variable conductance heat pipes comprising a first operating temperature range, and wherein the electronics compartment heat pipes comprise variable conductance heat pipes comprising a second operating temperature range; wherein the thermal insulation comprises at least one of: a) an aerogel; or b) a vacuum panel insulation; wherein the thermal insulation comprises an inner layer comprising a polyimide foam; and wherein the thermal insulation comprises an outer layer comprising a vacuum sealed aerogel insulation. firebox heat pipes adjacent to the firebox on an evaporator end and extending to an exterior surface of the battery pack on a condenser end; and electronics compartment heat pipes extending from within the electronics compartment on an evaporator's end and extending through the thermal insulation to the exterior surface of the battery pack on a condenser end; wherein the firebox heat pipes comprise variable conductance heat pipes and the electronics compartment heat pipes comprise variable conductance heat pipes , and wherein the firebox heat pipes comprise variable conductance heat pipes comprising a first operating temperature range, and wherein the electronics compartment heat pipes comprise variable conductance heat pipes comprising a second operating temperature range; wherein the thermal insulation comprises at least one of: a) an aerogel; or b) a vacuum panel insulation; wherein the thermal insulation comprises an inner layer comprising a polyimide foam; and wherein the thermal insulation comprises an outer layer comprising a vacuum sealed aerogel insulation. <EOS>