ORIGINAL: CGRetired
I have preached this for several years now. What I use as a quick check is the Voltwatch2. It is no replacement for a voltmeter, but is a very good tool for checking the battery condition before and after each flight.
CGr.
The voltage looked good (not great - but good) until I put a load on it. Then if fell flat.
I've been a crew chief for a multi-car SCCAnational team. The pre-weekend, pre-day, and pre-session check lists were very detailed. Just haven't smelled to coffee (until today) to apply a similar approach to an RCairplane. Past lives I had a Class Alicense. Ditto for a tractor trailer.