Amiga 2000, 3000, 4000 and A501 512k RAM all suffer from a common problem, the rechargeable RTC battery. It only really lasts about 6 years before it starts leaking corrosive battery acid all over your motherboard. The really bad thing about these stupid batteries is that if left untreated can pretty much ruin the motherboard. You see the battery acid flows along the copper traces and eats them up in the process. Depending on the model it can ruin, for instance, the RTC circuit and CPU socket of an A2000. The Amber circuit (VGA) of the A3000 and SIMM sockets on the A4000.
So if you still have these batteries clip them off immediately.
Replacements
They still do sell replacements and you can solder a new one on every 6 years or so. Or you could solder wires to the battery termials and to the motherboard and encase it in heatshrink or electrical tape or something and put it off the path of destruction. Then you need only solder on a new battery to the wires or use clips so you don't need to solder it every 6 years. This has the advantage of still using the recharging circuit built into the Amiga and the proper voltage of the RTC at 3.6v.
Here is a link to the actual battery used in the Amiga:
http://www.newark.com/varta/55608303059 ... p/06WX2749
Another option is to get a 3.6v cordless phone rechargeable battery pack and solder wires to the motherboard so the pack can stay velcroed out of harms way. These batteries usually don't leak and can last quite a long time.
Another option that I have seen is using a button cell replacement CR 2032 mounted on a circuit board that has a diode to negate the Amiga's recharge circuit as you do not want to recharge a CR-2032. Here is a link for that option:
http://amigakit.leamancomputing.com/cat ... ts_id=1093
I have read about people that use a rechargeable 2032 coin cell and let the Amiga Charge circuit charge it. Never do that as those batteries are not designed to be charged in the way the Amiga charges batteries. It could and probably will explode after so long.
Something I thought of recently as I had to replace a corroded battery on an old PowerMac was that you could use that 1/2AA battery that the Mac uses as long as you also use the diode to prevent charging. The advantage to these is that the voltage is the same at 3.6v. The CR2032 works but seems I recall reading that the lower voltage could cause problems with some RTC chips.
So what options do you use?