The aforementioned $5 tester is the one I've used for years; I can also use it to get a flashlight's amp draw, measure resistance, check household electrical outlets, etc, something battery testers cannot do. And I could pay many times more for a meter that's slightly more accurate, but would make no difference as far as flashlight applications are concerned.
Thanks. I may just decide to save some money and get the one you use. O.K., so how do I use it? Sorry, I really have no clue.