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CMOS battery started to leak - quick suggestions?

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First post, by deksar

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Greetings.

I got an 386 motherboard with an ntegrated on-chip AM386DX-40 CPU. The battery seems started to leak on the motherboard.

I got two spare batteries, however, I got also EXT BAT jumper, and instead of, removing whole the motherboard and soldering and such - each time the battery dies, I'm looking for easier solution for replacement.

Questions;
-Would the CMOS work correctly with CR2032 battery on EXT BAT? If not, what would you recommend me instead of it? And do I need additional diodes alongside the new battery? Or simply connecting a battery would be enough?
-There're 4 pins, I assume the 1st and the 4th pins are + and - ones. Am I right?

Thanks a lot!

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Reply 1 of 2, by jakethompson1

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I use the EXT BAT header.
Sometimes the middle two pins use a jumper over them in order to use (and charge) the external battery and sometimes they don't. Additional diodes are needed if the board attempts to charge a battery connected to the EXT header.
A CR2032 may or may not be enough voltage. On some of the boards I have, it is enough for the CMOS to not lose its settings, but the date/time freezes while the board is powered off. The EXT header was originally intended for a 4.5V battery, not a 3V one; like this Rayovac "Computer Clock Battery": https://i.imgur.com/FG82OJo.jpg
I use an external 3xAA battery pack with those with a wire and connector for the 4-pin header. There used to be a pre-made one for sale at DigiKey but it's discontinued, so you'd have to make the cable yourself.

Reply 2 of 2, by deksar

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Thanks for your reply and the idea.

So having 3xAA (1.5 Volt each?) batteries set like this; https://m.media-amazon.com/images/I/51cd3prsiIL._AC_.jpg
and connecting + to the pin1 and - to the pin4 would solve it all? Do I need extra diodes in case like this?

I got a jumper in pin2 and pin3 by the default, in EXT BAT on the motherboard. I guess that's to use the internal battery, as you said. And this jumper should be removed when using EXT BAT, right?
Would there be any difference between using AA 1.5V and AAA 1.5V batteries? Would an AAA battery work as well?

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