When driving big mountains (hint they are not in Alabama ), Prius drivers with data monitoring devices ought to take a peak at the maximum HV battery temperature. It is common to reach 45 oC, which has been stated as the highest 'happy' temperature for NiMH. There and higher, I turn on the cabin A/C in flow-through (not recirc) mode. Cooling then proceeds at about 1 oC per 5 minutes. Not surprising, the most battery heating is on the downhill side of the mountain. Not restricted to summertime operations.

It may be that I am extending my HV battery life by actively participating in its thermal management. Or, is this just another example of Prius nerd-dom? No evidence pointing either way from here, except that at 105 k odometer miles, my max and min module voltages track within 0.15 volts, almost always.

The exceptions occur on the cold side. If you ask much from the HV battery when it is below about 8 oC, that voltage spread can easily triple. This is the other domain where (perhaps) we can actively participate in HV battery longevity. After a cold-soak startup, be gentle for a while with those foot-pedals.

Have not explored the (analogous) role of using the cabin heater to get the HV battery into its thermal happy-place.

DAS