The 1000 and 500 dont have batteries. As pointed out, the 500 does have a battery in (some models at least) the RAM expansion. That shouldnt be able to leak and ruin the Amiga, but may ruin the memory board. I wouldnt worry too much about that.
The 2000 though, you absolutely should check ASAP and either replace with a 3.6V barrel NiMH or add a battery clip and diode and switch to lithium watch batteries.
