Product review (5 stars): Works great, long battery life
Uses a 9 volt battery so it has a lot of run time. I got it to measure the engine temperature in a sailboat. It works fine. Got a 5 meter thermocouple for $5 and hooked it up.
Accidentally left the display powered up overnight. It was still running the next day just fine.
Would highly recommend this as an accurate and inexpensive way to get an engine temp display if all you have is an idiot light.