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 (135, 235, 385) comprising: firebox heat pipes (135, 235, 385) 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 (135, 235, 385) 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 (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) and the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385), and wherein the firebox heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) comprising a first operating temperature range, and wherein the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) 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 (135, 235, 385) comprising: firebox heat pipes (135, 235, 385) 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 (135, 235, 385) 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 (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) and the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385), and wherein the firebox heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) comprising a first operating temperature range, and wherein the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) 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 (135, 235, 385) 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 (135, 235, 385) 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 (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) and the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385), and wherein the firebox heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) comprising a first operating temperature range, and wherein the electronics compartment heat pipes (135, 235, 385) comprise variable conductance heat pipes (135, 235, 385) 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.