The final day of the Chevy Volt tear down has definitely been the most interesting. After dropping the battery pack last night, we completed the removal of all electronic modules in the vehicle, and got a chance to see the entire assembly of Printed Circuit Boards (PCBs) on a viewing table. Congratulations to General Motors are due for the design of such a forward looking and complex vehicle. The battery control and utilization easily doubles the number of PCBs required in the car compared to a conventional gas system.

The battery pack is arranged in a T-shape fitting under the central axis of the car and the rear seats. A dedicated liquid coolant loop is used to maintain the temperature of the Li-ion cells at a precise temperature. This is required both during discharge and battery charging. The cells are arranged in a series of plastic “blades”. Interestingly, there are a total of 135 blades in the pack. The Volt specs claim 96 Li-ion cell groups are placed in series and one would expect the blade count to be close to this number. The battery pack will have to be analyzed further to understand this discrepancy. Numerous temperature sensors and voltage sensors feed four separate battery controllers placed on top of the pack. The battery controllers use ASICs branded with the LG Chem label and each controller has a separate PCB layout and design.

At the PCB and Integrated Circuit level, the major socket holder for the control processors is Freescale. The PCB design is quite advanced for an automotive application where feature minimization is not critical, with tight design rules and compact Surface Mount Devices. The PCB layout has open space that is clearly anticipating future design modifications, and there are many test points on the boards. The Volt has a surprising number of actively cooled modules. There are four liquid cooled components (the Inverter/Converter, Gas Engine, Battery Pack, and external Battery charger). As well, the step-down DC converter under the trunk is air cooled with a fan.

All in all, a very impressive design. Next to come; digging into the battery pack, and a deeper view of the control electronics.

JST