Lithium Battery Replacement Help

[Castellen]

Actually the NiMH batteries can still leak after a while, but they do tend to last a bit longer than the original NiCd batteries.
Varta rate their 3/V80H NiMH having a service life of approx 6 years @20°C.
From experience, the NiMH begin leaking after about 10 years, but some people report them leaking a lot sooner.

As for the lithium battery modification, the guide on Aminet is OK, but I'd suggest using a schottkey diode, or one with a low fowrard voltage drop (0.2-0.3V).
The lithium batteries are rated at 3.6V, and with a standard silicon diode's fwd voltage drop of 0.6-0.7V, that's right on the edge of the real time clock's operating voltage.

If you want to do the standard battery replacement, there's a guide I've written here:
http://amiga.serveftp.net/battery.html


Hmm, I really must take some better photos one of these days, those ones suck!
Doesn't help that my digital camera has a resoloution measured in kilopixels :-)

[Castellen]

For diode part numbers, I can't quite recall all the individual specs from various catalogues :-P
Usually I find it easier to use whatever is closest to hand.  Go to your local electronics shop and choose the first low loss diode you some accross.  Most schottky diodes will do the job perfectly.  It only has to conduct a few µA, so something with a fwd current rating of 100mA is more than adequate.
I've got a bunch of 1N6650 diodes laying about here I've been using in various random projects.  That would fit the bill nicely.

From the RP5C01 real time clock datasheet, the minimum data retention voltage is 2.2V.  So if you had a 3.0V battery, with a 0.7 fwd voltage drop diode in series, that's 2.3V at the RTC, 0.1V above the minimum required.
Obviously it will work, but with 0.2/0.3V diode, it'll work for longer as the battery's terminal voltage has to drop about 0.5V until the clock's time is lost.

As for the contents of NiMH batteries, I don't know much about chemistry, but I do know I've spent quite a few hours repairing equipment (not just computer) which has had PCB damage due to leaking NiMH batteries.
While I'd suggest they're a much better alternative to NiCd batteries, don't be under the impression they'll never need replacing.