Lots of things you can do!

Easiest is to get one of these battery clips with 2 wires and hook that up to the mainboard. The voltage written on your battery will tell you what battery clip you need to get

If you are handy with a soldering iron you can desolder the battery from the motherboard. I recently had a 486 board with the same type of battery and had to remove it:

You can buy the same type of batteries and solder a new one in, alternatively you can just buy a AAA/AA style battery holder and make one up yourself to plug in. Alternatively you can buy a premade battery like this one:
http://jaycar.com.au/productView.asp?ID=SB241 … ry&form=KEYWORD

This is what I ended up using for the above board. They are sealed to help prevent leaks. Be aware that if you use standard AA/AAA batteries in a holder, that these batteries can leak and the acid will destroy components. (I lost a soundcard this way back in the mid 90's). Its best to try and mount the batteries where they won't leak on anything if possible.

The voltage you need is 3.6V. Near your battery on the motherboard should be a row of 4 vertical pins, maybe one in the middle is missing. It should be labeled EXT BATT or similiar. In my pictures above you can see it immediately to the right of the battery, to the left of the mounting hole. If it has a jumper over the pins then remove it. Then you can plug in the external battery holder.
It is probably a good idea to remove the old battery from the motherboard even if you are using an external battery, so the old battery doesn't leak and corrode the tracks on the board. Corrosion can travel along the metal inside the board too. There are plenty of guides on desoldering on the internet if you google for them, its actually very easy, but practice on some old boards you aren't worried about first 😀

Maybe you can replace it with one of these?

Go to: http://www.interstatebatteries.com and type in product code NIC2510

These seem to have exact same ratings as one of my 386 motherboards. I'm not sure if that's the standard.

Yep that's a standard motherboard battery. I'd still recommend an external battery though as they are much easier to replace.

> You can buy the same type of batteries

So it will leak again a few years later...
Putting NiCd batteries onto PCBs is a constructional defect.

(If your board has an extenal battery connector headers...)

This is what I did to one of my 486 boards :

Removed the leaking dead battery (de-soldered) :
De-soldered a coin-cell battery socket from another unused motherboard.

Cut out a pc speaker connector with the wires. Soldered to the li-ion battery holder. And the connector is connected to the "External Battery" header on the motherboard.

I'm not good at soldering, and the picture shows my genious work where the wires are swapped! 😁 (Thanks to h-a-l-9000 for pointing out the mistake! 😀) So, anyway, I just need to turn the connector the other way round to connect to the header on the motherboard.

@Malik:

So it's ok to replace it with one that has a slightly smaller voltage? I always wondered about that. The "barrel type" battery is a 3.6v and the one you attach to the header is 3v I'm assuming? or is there a 3.6 coin battery you use?

Jan3Sobieski wrote:

@Malik:

So it's ok to replace it with one that has a slightly smaller voltage? I always wondered about that. The "barrel type" battery is a 3.6v and the one you attach to the header is 3v I'm assuming? or is there a 3.6 coin battery you use?

It's 3v, as you have said. So far no problems in maintaining the CMOS data in memory.

I've always feared that the battery would run out in my 486 and I would have trouble finding a new one, but I just looked inside the machine and it's just a regular lithium battery in it. Heh.

Lucky you. 😀

Thanks for the replies, everyone. I'll try your suggestions and see what happens.

Managed to get a picture today. Next to the battery is a two-pin connector marked Power Ctrl - JP3. Is that possibly an external battery connector? There's nothing else nearby. Sorry the picture is blurry my camera sucks.

Whoops. Just noticed another connector right next to it (I'm blind) called Ext Battery. That must be it, eh? It's a 4-pin connector with only 3 pins.

Ok, so managed to desolder the barrel battery off the motherboard (only a minor singe on my finger in the process). I do have a couple other motheboard lying around wtih coin-style batteries in them. What do I need to have and do to hook one of them up to my 486? Will any small cables with a 4-pin end and two wires work? Like a PC Speaker cable or a CD-ROM audio cable or something? Which wires need to match up to what and such? Thanks in advance.

Looks like a PC speaker cable should indeed work, as I seem to remember them using the outer two pins as in Malik's picutre. Malik or h-a-l-9000 might know which way it should need to be hooked up since it sounds like they have dealt with that.

Don't forget to remove the old battery because hooking up multiple batteries at the same time could result in nasty things like leaking/explosion.

Yeah, as I said I managed to remove the older battery. Would a CD-ROM audio cable work though? The PC Speaker cable I thought I could use has the wrong end on one side (the smaller 2-pin connector). The CD-Rom audio cable has 3 wires but two of them are on either end of the thing. Being the same connecting end I assume there's no difference unless the wires themselves are somehow different. But I could just ignore the third wire altogether? Or remove it somehow? I know nothing about this stuff, but I can follow instructions very well! I'll wait for h-a-l-9000 or someone with knowledge to respond.

I use the continuity tester in the multimeter to check which side is ground, the other side is + then. Or sometimes I already see which pin is connected to the ground / + traces.

The Power Ctrl - JP3 is not necessarily related to the battery. The mainboard manual would be handy.

As long as you can find a cable that fits and has wires on the pins you need, it should work for your purposes. If you gently pry and hold up the plastic retaining tab on the connector over the unwanted middle pin with a micro-screwdriver, you can then pull the extra wire out (pin and all!).

As far as the pins go, they're simply numbered from 1-4 (the Ext Battery pins). Is there any general rule as to which is positive/negative/ground/whatever in that type of instance?

The Power Ctrl - JP3 is not necessarily related to the battery. The mainboard manual would be handy.

I definitely don't have that. I picked this rig up at a rummage sale.

Do you have a multimeter? h-a-l-9000's idea of using a continuity tester or ohmmeter function to figure out which one is ground is a straightforward solution.

Ot the example board I just pulled out the single pin (1) is + and (4) is -.