TonyWilliams wrote:Imagine the car sitting in 122F / 50C Phoenix with the sun heating the sheet metal and interior to 140F / 60C or above. If the battery were heat sunk to the chassis, that scenario would tend to heat the battery, not cool it.
I think we might be going off on a tangent, but perhaps it's an interesting one. Yes, you are right, that would be a distinct implied disadvantage of this design. To be honest, I don't know how well the body acts as a heat sink. It would appear logical, and it's been repeated here a few times. I will try to dig up a few other sources, if they existed.
Aside from Luke's recent data
, we don't know much about solar loading in Phoenix. His battery seemed to stay relatively cool. Unfortunately, he did not record ambient temps and only had the max daily temp for Phoenix available.
The times when the chassis is cool, the battery seems to only get got from repetitive QC-ing. I've observed the battery COOL DOWN from 136F while driving almost 90 miles. Only one scenario would not provide cooling of the battery, according to the CODA engineer that extensively tested the LEAF; that is, repetitive uphill with stops on the hill and at gross weight.
Interesting! Would you know if CODA instrumented the car better? One would hope so. Any other observations they shared?
I remember reading something from Nissan implying that more heat was developed during charging than driving. There was another debate about how the charging proces was endothermic. I don't believe that it is. I'm pretty sure that discharge is not endothermic either, although very little heat is developed under normal circumstances. With that I aree.
At what rate did heat develop in the battery when racing on the track? If it was around 1 kW, perhaps it was simply absorbed by the battery mass? If Leaf's battery pack was not heat sunk, the only explanation would be vastly superior battery chemistry. While that's a possibility, I would have hard time believing that.
For what it's worth, although my instrumentation is non-existent, I believe that the battery pack in the ActiveE heats up faster. Perhaps twice as fast as in the Leaf. It could be my location, but with the exception of cooler temps after level 2 charging, I have never once perceived the benefit of active cooling in that car.