Engineering is a highly iterative process. Sometimes new data causes an entire redesign, often for the better. University of Washington EcoCAR 2 team members have devised several iterations of a battery cooling system, but with A123 Systems’ help, they’ve finally hit the mark.
Four engineers are designing a system to cool the battery pack for UW’s proposed vehicle architecture. Batteries generate heat when in use, so cooling via air or fluid is necessary to avoid damage. The main issue is that the ambient air at the final competition in Yuma, AZ is going to be about 40 degrees Celsius, and the A123 Systems batteries shut down at 50 degrees Celsius. After much brainstorming, the team’s initial thought was to run coolant through battery cooling plates and then through a radiator to dissipate the heat. They crunched thermodynamic data and learned that, in order to be effective in Yuma, the system would have to pump approximately 100 gallons/minute… which is completely unrealistic! UW needed to find an alternative.
After further deliberation, the team decided to use a thermodynamic refrigeration cycle. This system is similar to a refrigerator: Coolant is compressed to raise pressure through the radiator, heat is dissipated, and then the coolant is allowed to expand to add a magnitude of cooling. The system is a little more complicated and requires more power, but the UW thought they were headed in the right direction.
However, things changed yet again. At the Winter Workshop in Austin, A123 Systems representatives showed the team that cooling is not going to be as critical as they had thought. The batteries won’t heat up as much as predicted so UW had grossly over-engineered the cooling system. With A123’s input, the team re-redesigned a cooling system that integrates the coolant and radiator of the Chevy Malibu’s existing A/C system. This is a much simpler, smaller and more elegant solution than UW’s original design. The team thanks A123 Systems’ representatives for being so helpful in guiding them towards a much more feasible and realistic design!