I just want to go into a bit of detail about why we have set the low temp and the Hi temperature limits we have set for the charging.
Got this from a NIMH battery manual:
Low temperatures (e.g. -15C (5F)) will obviously reduce Ni-Cd and Ni-MH battery discharge rate. At -20C electrolyte is at its freezing point, charge speed will greatly slow down. At low temperature (under -15C (5F)) charge will raise the internal gas pressure and probably unseal the safety vent. Ambient temperature of 5C (41F) to 30C(86F) is the best range to get effective charge. Generally with temperature rising charge efficiency will become higher. But when the temperature rises to 45C (113F)or higher, the materials performance in the battery will be degenerated and battery service life will be shorten greatly.
If we want to charge in the cold, take the car for a ride to get both the car and the pack heated up. If the ambient is very cold, one could put a small electric heater in the car, since we have an AC cord for the charger going in anyways.
The pack heat and the electric heater will keep the car and the pack in the 41-86F range
We also need to consider the situation where the pack is frozen, but the car has warmed up in the sun. I still advise taking a ride to warm up the pack, before charging, as the warm air will take some time to thoroughly thaw the pack.
We do not allow charging when the ambient inlet air temp is < 40F, or >97F or when the outlet temp (battery temp) is < 48 F or >107F . these conservative values will minimize the chances of the pack being charged when in a temperature zone that could damage or otherwise reduce the effectiveness. The Max inlet and max outlet temps are adjustable via the tech edit, but the minimums are fixed constants at this point.