GM’s Battery Program

General Motors currently has development contracts with Johnson Controls-Saft and A123-Cobasys to work on lithium ion battery packs, initially for the plug-in hybrid Vue program. The lessons learned from that will also be applied to the Volt program although the balance of the battery chemistry will be different for that program since it’s primarily battery driven and requires greater energy than the parallel hybrid Vue. Joe LoGrasso is the Engineering Manager for Hybrid Energy Storage Systems and he gave an overview of the differing battery requirements for the two-mode, plug-in and series hybrids, ranging from short-range low-speed electric to 40+ miles. The E-Flex needs substantially higher power output than the parallel hybrids and much more energy density. Since the series hybrid has to get all of it’s motive power from the battery, and can’t rely on an engine for power, the battery has to do much more. 

Lithium batteries have the energy density and power output, and tend hold the power when sitting better than other types. The biggest problems that need to be conquered are lifespan, cold temperature performance and most importantly, robustness and abuse tolerance. Since the battery pack is built up from hundreds or thousands of individual cells, the interconnects that tie all the individual cells together have to be very carefully constructed in order to ensure that the pack survives the life of the vehicle. The process goes from developing individual cells to meet the performance requirements, integrating those cells into a pack and then finally integrating that pack into the vehicle system. While lithium batteries have been used in consumer electronics devices for many years, combining them into large format packs for use in the automotive environment is relatively new. Another problem that has to be dealt with is scaling up the construction of potentially tens of millions of larger format cells, in a consistent manner to ensure that they perform consistently and reliably in automotive applications. After all, no car-maker wants to be facing a large-scale battery recall like laptop manufacturers did in early 2006.  

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