A month ago I've checked the battery of my 13 years old A500+ (... my first Amiga!). It was a disaster!
It was a stroke of luck because the battery had a lot of leakage but hasn't yet reached the motherboard.
Now I've changed the battery placing it in a safer place (in the right side of the case, near the floppy) with two wires soldered on the motherboard.
Alex