by surfingslovak (Posted Mon, 20 May 2013 21:41:48 GMT)
Thanks for that! I wasn't following that thread. Should this be confirmed, and the pack needed more than half a day to cool sufficiently, then the charge time, and by extension the charge rate, should be less relevant. C/2 charging will likely offer little benefit over other C rates. The thermal mass of a passively cooled battery is probably the key difference between the study referenced on the first page of this thread and the LEAF. A small consumer cell should take much less time to dissipate any heat generated during the charging process than a 600 lbs battery pack.
TomT wrote:
Agreed. The Leaf's pack has substantial thermal mass and equalizes very slowly. This can be either a plus or a minus depending on circumstances...
I don't think that is correct. My guess about the time constant (referenced by Reg in another thread) is that it is around 8-12 hours. Physically, the time constant represents the time it takes the system's step response to reach 1-1/e or approximately 63.2% of its final (asymptotic) value.
Stoaty wrote:
surfingslovak wrote:
That said, please keep in mind that battery temperature will equalize with ambient after a few hours...
I don't think that is correct. My guess about the time constant (referenced by Reg in another thread) is that it is around 8-12 hours. Physically, the time constant represents the time it takes the system's step response to reach 1-1/e or approximately 63.2% of its final (asymptotic) value.
Thanks for that! I wasn't following that thread. Should this be confirmed, and the pack needed more than half a day to cool sufficiently, then the charge time, and by extension the charge rate, should be less relevant. C/2 charging will likely offer little benefit over other C rates. The thermal mass of a passively cooled battery is probably the key difference between the study referenced on the first page of this thread and the LEAF. A small consumer cell should take much less time to dissipate any heat generated during the charging process than a 600 lbs battery pack.