Lots of choices mate. Bit silly talking about batteries when there are hundreds of thousands of navigation units out there happily sitting on the dash and in the hot, hot sun all day long. The temps that can be experienced in a vehicle is nothing compared to the internal temperature a battery can get to while in use and when recharging.
In other words ...
Go to Maps screen, exit fullscreen, click on Nav> scroll to the very end> Map version.
But, I still don't know the Command version..! I have to do more research.
Apparently in addition to the two strips there is a smaller strip just below the heater panel with a locking button on it. You can loosen that and lift it down to release the heater panel.
This link appears to have more detail on the procedure.