Today I purchased yet another battery powered tool, an airless paint sprayer, again from RYOBI, and this one came with two lithium-ion batteries and a fancier charger.

Just for grins (since it's brand new, if I break it, I can take it back to the store an get a replacement.) I plugged in one of the "permanently dead" batteries with which the old charger had absolutely no luck, and found it does, indeed charge in the new charger, and, after a few minutes in the new charger, it seems to charge normally in the old one as well. What a surprise!

I'll pay close attention to how this works over time.

RE