rnlcarlov wrote:If you say the 12V battery is charged during L1 or L2 charging, then a possible solution would be to leave the cabin blower on during charging and have an EVSE with ajustable output (6A to 14A, for example). If you have a general idea of how much %/hour it charges at each speed, you can set it up so that it finishes charging right when you need it, avoiding running down the 12V battery.
Of course this only works is the ambient temperature is low enough at night.
I thought that would be a good idea too. A few nights ago I did set my wife's car up to have air circulation thru the pack while L1 charging. It didn't work out well though. it appears that heat given off during charging is significant whether the Charge rate is L1 or L2. One of the winter time strategy threads touches on this, as people having better luck keeping the battery warmer charging on L1 than when charging on L2. Basically, active ventilation with ambient air around 10 F cooler than battery temps will only mitigate cell temperature increases during charging, but not reduce those temperatures much, if at all. So the shorter charge time and all night active ventilation (at medium fan speed) has the largest impact. Higher fan speeds cool less well due to the fan motor waste heat, fighting the additional back pressure on it at higher speeds.
So the bottom line seems to be that L2 charging and ventilating the battery pack continuously as long as the Ambient temperature is lower than the average cell temperature. During charging it holds off further cell temperature increase and before or after charging it makes a significant difference in the morning temperature (9 F to 11 F) of the pack compared with doing nothing at all . . . so far.
I have rigged up a 12 volt 7 amp battery charger that I had as surplus to supplement the 12 volt system overnight (thru the accessory power port) so that I can run my wife's fan all night tonight and see how it compares to previous data from her daily parking and driving. She is moderately averse to taking the time and energy to do what I do with my car while driving, etc. Using AC to the pack etc. The AC to the pack makes a huge difference in accumulation of heat in the pack throughout the day.
No Active intervention:
Her car will arrive home with 102 F highest cell with ~99 F average for the whole pack. Then after sitting in a 77 F average temperature garage for 13 hours and charging around 4 bars (L2) during that time. By morning departure time, the Pack will have a highest cell temp of 97 F and a whole pack average of 95 F
With active intervention: Running AC through the pack all day whenever driving. Sharing with the cabin as much as needed to stay nice and comfortable! Then active cooling as best possible, with ambient air when home in the garage and 7 to 13 bars of L2 charging during that time. I am able to keep the peak highest cell temperature at or below 91 F and morning departure pack temperature of 78 F to 82 F
A striking difference IMO. The key is to make it simpler and more automatic to achieve!