DeWalt Tools, Replacement Battery question?

Not trying to make fun or be snooty but if you have six tools they deserve 1 more good battery. Frankly, at my age, 74, I rarely use battery tools, because no more than I use them, it's difficult to keep them all in shape.

I've bought camera batteries from the cheap ebay sellers, and there is no doubt that, generally, the performance is NOT on a par. Some of them don't even have the same protection, AKA the termal sensor used by the charger