It looks like it was designed to use either of two sizes of battery, so it's pretty flexible. You can use a CR2032 (or rechargeable equivalent). If you use a CR2032, or any other non-rechargeable battery, a lot of people recommend putting a diode in series with it, to prevent the battery from being damaged by the charging circuit.

debs3759 wrote on 2023-08-09, 21:42:

It looks like it was designed to use either of two sizes of battery, so it's pretty flexible. You can use a CR2032 (or rechargeable equivalent).

So if I buy a CR2032 socket and a rechargeable battery, it would work & recharge? Or do I have to buy specific socket/battery to make it happen?

A rechargeable battery such as an ML2032 will do the job. Same size as a CR2032 so the same socket. I can't check the distance between contacts on the socket, as most of my stuff is boxed up until carpets are fitted next week, but I'm sure they will work, even if it means bending the legs to fit.

I just checked, and LIR2032 is rechargeable as well. LIR2032 is 3.6V, ML2032 is 3.0V, so the LIR2032 is the best replacement for a Varta

I can't tell if that 3-pin header between the missing battery and the keyboard connector, above the middle capacitor in the cropped image given here, is an External Battery jumper or something else. If it's External Battery you can connect 4.5V 3xAA non-rechargeable battery pack across it.

Many solutions to this issue... there's even a drop-in replacement for the barrel battery with diode and everything, e.g.: https://github.com/scrapcomputing/BarrelBatteryBlaster

If you connect something with the voltage too low you may find that the board keeps its settings but the clock freezes in place with the power off. I find that with some boards I have, where 3V (CR2032) isn't enough but 4.5V (3xAA alkaline) is. The original barrel battery was 3.6V

debs3759 wrote on 2023-08-10, 00:39:

A rechargeable battery such as an ML2032 will do the job. Same size as a CR2032 so the same socket. I can't check the distance between contacts on the socket, as most of my stuff is boxed up until carpets are fitted next week, but I'm sure they will work, even if it means bending the legs to fit.

Is it safe to just apply 5V across a ML2032 or LIR2032 as if it were NiCd? I thought lithium-ion required a more sophisticated charging circuit...

jakethompson1 wrote on 2023-08-10, 01:16:

I can't tell if that 3-pin header between the missing battery and the keyboard connector, above the middle capacitor in the cropped image given here, is an External Battery jumper or something else.

If it helps, I uploaded a image of the full motherboard in another thread: download/file.php?id=170196&mode=view
Looking at it closer, it seems to have 4 pins; shouldn't an external battery jumper have 3 pins so you don't mix up the polarity?

jakethompson1 wrote on 2023-08-10, 01:16:

...there's even a drop-in replacement for the barrel battery with diode and everything...

Maybe if there was a way to mount it horizontally, as otherwise it might get in the way of the first PCI slot.

alexparr wrote on 2023-08-10, 02:43:

jakethompson1 wrote on 2023-08-10, 01:16:

I can't tell if that 3-pin header between the missing battery and the keyboard connector, above the middle capacitor in the cropped image given here, is an External Battery jumper or something else.

If it helps, I uploaded a image of the full motherboard in another thread: download/file.php?id=170196&mode=view
Looking at it closer, it seems to have 4 pins; shouldn't an external battery jumper have 3 pins so you don't mix up the polarity?

I'm talking about the one further down that currently has a jumper on it.
The 4-pin header is likely for a PS/2 mouse port.

jakethompson1 wrote on 2023-08-10, 03:02:

I'm talking about the one further down that currently has a jumper on it.
The 4-pin header is likely for a PS/2 mouse port.

Hmm, it could very well be a PS/2 header. I'll have to look into that. Same goes for the one with a jumper on it; I'll check it out at some point later today.

Looking at the 3-pin header, I don't think that's meant for a battery. I don't know what it's for.