Those external battery connectors in old boards use the two outer pins, 1 and 4. Usually 1 is connected to the battery + and 4 to -, but you should check because it's not always the case. The pin that is connected to ground will be the battery -.

What you can do if your pack has a different connector is to replace it with a 4-pin Dupont-style connector (or just cut it and solder a PC speaker connector if you don't have the Dupont connectors and crimping tool).

Keep in mind that 2 alkaline batteries might not be enough to keep the CMOS settings/time, that's only 3V and there are two diodes that drop the voltage after the connector. 4.5V (3xAA or 3xAAA) will be much more likely to work.

Will a not a varta work too?

Like the rechargeable one the board originally had? Sure, but you don't need the external connector for that one, just solder it where the old one was.

Of course, if you use a NiCd barrel battery it will leak over the board at some point if it's not removed. But it should last a few years.

I meant a Not-A-varta battery cell socket.

https://github.com/wiretap-retro/Not-A-Varta-CR2032

AvocadoLongfall wrote on 2024-04-07, 02:06:

I meant a Not-A-varta battery cell socket.

https://github.com/wiretap-retro/Not-A-Varta-CR2032

It depends...
If you connect the non-varta module to the 4-pin header, the 3V voltage passes 2 (sometimes 3) diodes and the voltage drops to 2.x V. Original battery packs for this header with 3 or 4 cells had 3.6 / 4.5V.
If your chipset´s clock (or dedicated RTC circuit) works correctly with 2.x V everything´s fine, if it demands a higher voltage like >3V the clock will slow down.

You can solder the non-varta module in the place of the original battery instead, but you need to remove the resistor / diode that connects the battery to the charging circuitry of the mainboard in this case. The 3V battery voltage will pass just 1 diode in most cases so the voltage for the clock is a little higher. But sometimes it´s still not enough.

If you have some battery holder for 2 x AAA or AAAA cells you can connect it to the 4-pin header for a test. If the mainboard was disconnected from the PSU fo a couple of days and the clock is still correct afterwards, then the chipset is o.k. with 3V at the 4-pin connector and you can use the non-varta as well.

Oh, just found out that despite setting the hard disk and other settings in the bios without the cmos, the computer still remembers it after restarting and all games so far work and play well.

...and will reset to default values after a couple of hours.

While it is off or on?