I'm having a hard time finding a reasonable priced battery tester than I can trust without a second opinion. I've tried a few now and my current tester seems the best of the lot in it's price range. It's this one:
It has settings to test in/out of car, battery types, PB flooded, AGM, GEL, it reports both charge level and total health, it cost $6X.xx
My only real concern is the speed of the test. It takes about 5 seconds to return a result, which is good if it is accurate. I remember battery tests taking 30 minutes, maybe more, back in the day. Can they really properly load a battery and get trustable results in 5 seconds?