A transport refrigeration unit, comprising: a refrigeration unit, comprising: a compressor having a compressor outlet, the compressor being at least partially powered by a power pack, and a first heat exchanger having a first heat exchanger inlet and a first heat exchanger outlet; and a power supply unit, comprising: a second heat exchanger having a second heat exchanger inlet that is fluidly connected to the compressor outlet and a second heat exchanger outlet that is fluidly connected to the first heat exchanger inlet, and a battery arranged to provide electric power to the compressor; characterized in that: the power supply unit further comprises an insulated battery box, wherein the second heat exchanger and the battery are disposed within the insulated battery box, and wherein the second heat exchanger is configured to receive fluid flow from the compressor outlet such that the second heat exchanger generates waste heat that heats the interior of the insulated battery box. a refrigeration unit, comprising: a compressor having a compressor outlet, the compressor being at least partially powered by a power pack, and a first heat exchanger having a first heat exchanger inlet and a first heat exchanger outlet; and a power supply unit, comprising: a second heat exchanger having a second heat exchanger inlet that is fluidly connected to the compressor outlet and a second heat exchanger outlet that is fluidly connected to the first heat exchanger inlet, and a battery arranged to provide electric power to the compressor; characterized in that: the power supply unit further comprises an insulated battery box, wherein the second heat exchanger and the battery are disposed within the insulated battery box, and wherein the second heat exchanger is configured to receive fluid flow from the compressor outlet such that the second heat exchanger generates waste heat that heats the interior of the insulated battery box. a compressor having a compressor outlet, the compressor being at least partially powered by a power pack, and a first heat exchanger having a first heat exchanger inlet and a first heat exchanger outlet; and a power supply unit, comprising: a second heat exchanger having a second heat exchanger inlet that is fluidly connected to the compressor outlet and a second heat exchanger outlet that is fluidly connected to the first heat exchanger inlet, and a battery arranged to provide electric power to the compressor; characterized in that: the power supply unit further comprises an insulated battery box, wherein the second heat exchanger and the battery are disposed within the insulated battery box, and wherein the second heat exchanger is configured to receive fluid flow from the compressor outlet such that the second heat exchanger generates waste heat that heats the interior of the insulated battery box. a second heat exchanger having a second heat exchanger inlet that is fluidly connected to the compressor outlet and a second heat exchanger outlet that is fluidly connected to the first heat exchanger inlet, and a battery arranged to provide electric power to the compressor; characterized in that: the power supply unit further comprises an insulated battery box, wherein the second heat exchanger and the battery are disposed within the insulated battery box, and wherein the second heat exchanger is configured to receive fluid flow from the compressor outlet such that the second heat exchanger generates waste heat that heats the interior of the insulated battery box. the power supply unit further comprises an insulated battery box, wherein the second heat exchanger and the battery are disposed within the insulated battery box, and wherein the second heat exchanger is configured to receive fluid flow from the compressor outlet such that the second heat exchanger generates waste heat that heats the interior of the insulated battery box.