Totally agree that the ground based tool is a good thing.
My puzzlement is that the plane flies just fine with the batteries in question, they're nicely balanced both before and after use, they aren't any warmer after a flight than I'd expect. However the IR measurement with the ESR meter produces numbers that indicate there the batteries are tired. If they really are as tired as the numbers suggest I would have thought it would be obvious in flight. The complicating factor is that these batteries are my first 4 cell batteries for use in my first two balsa planes - maybe they really are tired and the planes are so much better than the EPP hybrids I've been flying that I don't realize they're not performing as well as they could.
I've decided I'm going to order a couple new batteries of exactly the same kind and see how they compare.
I wouldn't be surprised if these planes to experience an unfortunate and unplanned encounter with mother earth sooner or later, but if they do I hope it's because I get too ambitious and aggressive flying, not for a lame reason like tired batteries