It's usually not as simple as just adding a coin battery holder. The reason is these motherboards would usually have current supplied to the on-board battery to keep it charged. However, these batteries would usually be NiCD rechargeable which have different charging requirements than a modern lithium coin cell battery.

So you would first have to check the circuit to see if +5V is being supplied to the battery (on the battery + line). There is likely a diode that could be removed to disable the charging circuit. Then you could install a coin cell holder for a lithium coin cell battery.

Ok. Would it just be easier in this instance to just connect a wired battery to the EXT Battery header? Or is it just going to present the same issue?

Using an external battery will be fine. The circuits were typically designed to recharged the soldered battery, not the external battery.

Shponglefan wrote on 2026-04-15, 13:54:

Using an external battery will be fine. The circuits were typically designed to recharged the soldered battery, not the external battery.

Awesome, I'll try that as a first port of call then. Thanks!

If you cant find a chargeless hookup / cant disable the charge circuit, nimh cells are 'grocery store commodities' (rechargable AA cells), and are 'close enough' that the stupid charge system in the motherboard can charge them. They wont have maximal service life, but they can take a few years of punishment on that setup.

(NiCd battery uses a less intelligent charging system, that doesnt need fancy monitoring. Basically just +5v at some tiny trickle current. NiMH cells 'can' charge that way, but it breaks down the electrolyte and annode inside over time. NiMH chargers monitor cell resistance and voltage, and make adjustments to the input voltage and current, to avoid this issue. The barrel-bomb batteries on these boards have a vanishingly small miliampere value though, and by the perspective of a high drain NiMH AA array, is teensy. The damage done will be slow.)

Just be sure to use a 3 or 4 cell holder and velcro it in the case AWAY from the motherboard just in case.

(NiMH AA battery is nominally 1.2V, not 1.5V like alkaline battery. 3 in series is 3.6V, which is on target for a lithium cell replacement. 4 in series is 4.8V, which is in the ballpark for NiCD.)

Would I be good with one of these?

https://ebay.us/m/FlCMMZ

You'll need to pop the JST end off and put a 4 pin Dupont, but sure.

I'd look for one with 4 pin dupont already on.

The female version of these in this pack would work.

https://www.amazon.com/risingsaplings-CR2032- … y/dp/B0DG5KKDX3

Make sure the charging circuit is disabled.

jami3rez wrote on 2026-04-15, 17:08:

Would I be good with one of these?

https://ebay.us/m/FlCMMZ

No, those batteries are 3v3 at best. The rechargable battery on a mainboard tends to be 3v6 (3x 1v2 in series)
While it will work for a short time, for proper longer time operation you'll need 4v5,
remember that the external battery tends to be non rechargable and thus has a diode in series to stop any possible charging.
This diode tends to drop 0v6 which brings the voltage of a 3v3 battery down to 2v7 which tends to be too low.
When coming from 4v5, a diode voltage drop of 0v6 leaves 3v9 which is good to keep the cmos & rtc going.