If the original battery is rechargeable like NiCd or NiMH, you can't replace it with non-rechargeable lithium battery, as they don't tolerate being charged at all.

(Sure, it does not necessarily explode spectacularly and burn your house if you do charge it, but still the rule is don't recharge things that should not be recharged).

Sounds like a triple series NiCd arrangement. You could certainly convert the board cheaply and safely using AA rechargables and an external holder.

I used to do the CR2032 mod + diode but not anymore... I just replace the battery with a new 3.6v rechargeable one and call it a day. 😎

LIR2032 rechargeable may work. NiMH AAAs or AAs aren't a terrible idea either. The rechargeable coin cells will be 3.6v rather than 3v. Could also use a single non-coin rechargeable lithium ion battery like a common 18650 or 14500 etc. Not sure if that motherboard recharges its CMOS battery but it might be better to avoid lithium if it does though. Barrel battery may be NiMH rather than NiCd - hopefully, because NiCd is crap.

Fully charged NiMH is ~1.5V per cell, so I doubt the barrel uses it.

appiah4 wrote:

Just received a 486 board today, and it has a barrel battery on it. There is minimal leak and some surface corrosion, so I want to replace it with something safer. I was hoping to replace it with a CR2032 battery holder, but upon receiving it I noticed the battery on it is 3.6V, not 3V. What can this be replaced with?

The easiest solution I have found for these cases is to use the external 4-pin battery header (most 486 boards have one) and just build a AA battery pack with a PC speaker connector. 3 or 4 AAs should work, and you don't need diodes or soldering anything to the board. Just a AA holder and a speaker connector (you could use a couple of CR2032 as well).

appiah4 wrote:

Also, it looks like the battery was slid into place and glued on with some silicone, so I tried to pull on it a bit to see if it would come loose - it did not.. Do these batteries also get soldered on? Or is it just the silicon glue holding it? What's the safest way of removing it?

Yes, most likely it is soldered to the board. You can rock the battery back and forth while desoldering and that should easily break the glue bond.

I came across this site a while ago: http://pc-restorer.com/replacing-cmos-batteries-in-old-pcs/
Should answer all your questions and also provide you with the various alternatives.

Most motherboards from that era, that had a barrel battery, also had an external battery connector (looks very similar to a standard speaker connector), which is normally a non-rechargeable connection. I think that this is the easiest and most hassle free way of replacing the onboard battery.

If it helps any, here are photos of the battery and corrosion in question:

Also, here's the board if anyone can locate the external pattery header because I sure cant:

use an ohmmeter, check the battery's negative terminal's continuity to ground on the board

if it does have that, take the Clear CMOS jumper off but note which 2 pins are used when the battery is connected and the CMOS is NOT in clear mode. With the jumper off, test which of those 2 pins does NOT have continuity to the battery positive terminal (the one that goes to the battery goes to the internal battery and that's not what we want - we want the pin that goes back to the flash). Hook your external battery up between that pin and ground.

The other pin (that you use to clear it) may be ground, or you can otherwise use nearly any ground on the board. The resistor may be in the way though. The resistor is almost definitely between the "clear" pin and ground, to limit the current when discharging the supply (which likely has a bypass capacitor or two on it as well), so you'd want to find a different ground without a resistor in the way.

If you do it this way, your new clear CMOS method will simply be to pull the battery from that connector (to speed up the clearing, you could then put the jumper on the clear pin at that point, as you would when using the internal battery)

If the battery doesn't have continuity to ground, ignore this post, though it probably will.

I do what keropi does: buy new 3.6V NiCd batteries and solder them properly on there.

I'll take a look on my very similar board that I got this weekend that luckily had a small coin cell soldered on, but I'd expect the 4 pins with the jumper near the battery would be the header for the external connection.

I would not consider soldering any NiCd on boards. Even coins can leak as we saw with the Roland SCs. If it's got an external connector pull a long wire and move it away from the board. Someone will thank you in the next 20 years 😀

elod wrote:

but I'd expect the 4 pins with the jumper near the battery would be the header for the external connection.

You mean the jumper block that says "DX" and "SX" next to it? That's pretty clearly not for a battery. Or at least I am not aware of there being SX and DX batteries. Make sure to get a DX if so, in case your BIOS needs to do floating point math.

I wouldn't call a clear CMOS jumper an external battery connector either, but hey. Whatever works. It can be used as such but it is for clearing the CMOS. Most likely never intended to be used with external battery.

This is a copy paste from member appiah4's other thread touchng the same topic.

Notice that the pin number order is as it was shown in the picture in the other thread, to get it right you need to rotate the picture in this thread 90 degrees to the right. This is one of the reasons I really dislike when people start more than one thread about the same issue (even if in this case the threads started out a bit different).

You normally connect the external battery to pin 1 and 4, one of them is ground and the other + (the ones furthest away from each other). One of the pins is often marked with a "+" sign so you know which way to connect the cable. (Pin 1 should be + I would think but check that pin 4 is connected to ground with a DMM to make sure.)

Your battery header (or how I think your battery header works).

4 3 2 1 (Pin numbers)
- - + + "Pin 2" (+) is connected to the soldered on battery + and "pin 1" (+) is connected to the BIOS chip +, the jumper connects the two.

("Pin 3" could just aswell be "NC" = not connected but this dosn't matter.)

External battery - goes on "pin 4" and + on "pin 1", but as I wrote above double check with a DMM before connecting an external battery.

To remove the old barrel battery just clip the leads with a small pair of side cutters (nail clippers may work as well) and carefully twist it to break the silicone holding it on. Then, buy a 3 cell AAA or AA holder and 3 low self discharge NI-CD or NI-MH cells and connect it to the external battery header or solder the wires to the pads where the original battery is.

It's not rocket science people. :roll eyes:

Skyscraper wrote:

This is a copy paste from member appiah4's other thread touchng the same topic.

Notice that the pin number order is as it was shown in the picture in the other thread, to get it right you need to rotate the picture in this thread 90 degrees to the right. This is one of the reasons I really dislike when people start more than one thread about the same issue (even if in this case the threads started out a bit different).

..

Thank you for the very detailed information.. My intention on starting this thread was really not into getting into this much detail on the header pinout but I really appreciate your response in both threads for what it's worth.

kenrouholo wrote:

elod wrote:

but I'd expect the 4 pins with the jumper near the battery would be the header for the external connection.

You mean the jumper block that says "DX" and "SX" next to it? That's pretty clearly not for a battery. Or at least I am not aware of there being SX and DX batteries. Make sure to get a DX if so, in case your BIOS needs to do floating point math.

I think elod means the four pins in a row (J1) between R22 and the battery, rather than the block of 4 pins (J2/J3) for DX/SX. J1 looks like the external battery header to me as well.

The battery currently on the board is a GP60BNKx3 NiCd so I'm guessing it's rechargable, I'll remove it by chopping its legs off and find something suitable and rechargable to connect via the ext battery header, probably a 18650 3.7V rechargable and its holder fixed onto a suitable part of the case - thanks a lot for the help guys!

appiah4 wrote:

The battery currently on the board is a GP60BNKx3 NiCd so I'm guessing it's rechargable, I'll remove it by chopping its legs off and find something suitable and rechargable to connect via the ext battery header, probably a 18650 3.7V rechargable and its holder fixed onto a suitable part of the case - thanks a lot for the help guys!

The battery connected via the header is not charged. Also, avoid LiIon batteries. You need a battery holder with 2 or 3 aaa or aa batteries, they will last for a couple of years. I got the same board (different revision though). I should be able to run some tests tomorrow. The header usually has +- on it's extremes. The negative pin should be fairly easy to confirm with a continuity tester.

elod wrote:

appiah4 wrote:

The battery currently on the board is a GP60BNKx3 NiCd so I'm guessing it's rechargable, I'll remove it by chopping its legs off and find something suitable and rechargable to connect via the ext battery header, probably a 18650 3.7V rechargable and its holder fixed onto a suitable part of the case - thanks a lot for the help guys!

The battery connected via the header is not charged. Also, avoid LiIon batteries. You need a battery holder with 2 or 3 aaa or aa batteries, they will last for a couple of years. I got the same board (different revision though). I should be able to run some tests tomorrow. The header usually has +- on it's extremes. The negative pin should be fairly easy to confirm with a continuity tester.

Ok, thanks again. Just getting one of these, adding alkaline AAA batteries and connecting to the -/+ with dupont cables, minding polarity..

Cheers everyone 😀