A battery pack for use with a hybrid vehicle, the battery pack comprising: a housing; a plurality of battery cells contained within the housing, and an active thermal management system, including: a thermal channel configured to provide fluid communication between an interior of the housing of the battery pack and an exterior of the housing of the battery pack; at last one thermoelectric device configured to transfer heat from the battery cells /204) to the thermal channel; a device configured to control fluid flow via the thermal channel; and a controller configured to control the device to actively control heat transfer from the interior of the housing of the battery pack to the exterior of the housing of the battery pack to maintain the battery pack at a desired temperature, said battery pack being characterized in that: the battery cells are divided into first and second sets of battery cells (204a-c,204d-g), a direct current to direct current (DC-DC) converter is provided, contained within the housing, said active thermal management system is contained within the housing, said thermal channel being arranged through the battery pack with the first set of battery cells (204a-c) on a first side of the thermal channel and the second set of battery cells (204d-g) on an opposing second side of the thermal channel, two sets of thermoelectric devices (TEDs) (208a-d,208e-h) are provided on the two sides of the thermal channel, said TEDs (208a-d,208e-h) being configured to transfer heat from the battery cells and the DC-DC converter to the thermal channel, an insulator (216a,216b) arranged between each set of battery cells and the thermal channel and between the DC-DC converter and the thermal channel. a housing; a plurality of battery cells contained within the housing, and an active thermal management system, including: a thermal channel configured to provide fluid communication between an interior of the housing of the battery pack and an exterior of the housing of the battery pack; at last one thermoelectric device configured to transfer heat from the battery cells /204) to the thermal channel; a thermal channel configured to provide fluid communication between an interior of the housing of the battery pack and an exterior of the housing of the battery pack; at last one thermoelectric device configured to transfer heat from the battery cells /204) to the thermal channel; a device configured to control fluid flow via the thermal channel; and a controller configured to control the device to actively control heat transfer from the interior of the housing of the battery pack to the exterior of the housing of the battery pack to maintain the battery pack at a desired temperature, said battery pack being characterized in that: the battery cells are divided into first and second sets of battery cells (204a-c,204d-g), a direct current to direct current (DC-DC) converter is provided, contained within the housing, said active thermal management system is contained within the housing, said thermal channel being arranged through the battery pack with the first set of battery cells (204a-c) on a first side of the thermal channel and the second set of battery cells (204d-g) on an opposing second side of the thermal channel, two sets of thermoelectric devices (TEDs) (208a-d,208e-h) are provided on the two sides of the thermal channel, said TEDs (208a-d,208e-h) being configured to transfer heat from the battery cells and the DC-DC converter to the thermal channel, an insulator (216a,216b) arranged between each set of battery cells and the thermal channel and between the DC-DC converter and the thermal channel. the battery cells are divided into first and second sets of battery cells (204a-c,204d-g), a direct current to direct current (DC-DC) converter is provided, contained within the housing, said active thermal management system is contained within the housing, said thermal channel being arranged through the battery pack with the first set of battery cells (204a-c) on a first side of the thermal channel and the second set of battery cells (204d-g) on an opposing second side of the thermal channel, two sets of thermoelectric devices (TEDs) (208a-d,208e-h) are provided on the two sides of the thermal channel, said TEDs (208a-d,208e-h) being configured to transfer heat from the battery cells and the DC-DC converter to the thermal channel, an insulator (216a,216b) arranged between each set of battery cells and the thermal channel and between the DC-DC converter and the thermal channel.