Has anyone measure the temperature inside their cowling?

I am mounting a backup battery on the engine side of my firewall, and I don't want to exceed the battery's maximum temperature limit.

While looking for an answer to my question, I found this interesting fact -

"One thing to keep in mind is that most items under cowl don't see their highest temperatures until after engine shut down. The cylinders cool down and everything else heats up. The temperature rise after shut down for some components can be quite dramatic."

Given that fact, I could simply go flying and then check the temperature once I land & shutdown.