most likely just drain your battery.

You can test this out with a basic multi-meter. One pin is going to connect to ground, and the other wont. that pin goes to (-), the other (+). Easy peasy lemon squeezy.

einr wrote:

...or because a 3V CR2032 is not enough voltage (original battery is a 3.6V lithium barrel)

I've never encountered a single board that can't keep it's settings when fed with 3V instead of 3.6, so I wouldn't worry about that.

konc wrote:

einr wrote:

...or because a 3V CR2032 is not enough voltage (original battery is a 3.6V lithium barrel)

I've never encountered a single board that can't keep it's settings when fed with 3V instead of 3.6, so I wouldn't worry about that.

The problem is the barrel batteries are rechargeable - installing a regular lithium battery instead of a rechargeable is asking for trouble... For coin cell rechargeable 3.6v you should look for LR2032 (not CR2032) - but it's more expensive then a regular 3.6v barrel. What I like to do is remove the barrel batts and use 1 hole round pin sockets in place so I can stick a barrel battery in place for boards that I use, and remove the battery from the pin sockets when I'm not using the machine for longer periods of time to prevent leakage.

More specifically I use these: http://uk.rs-online.com/largeimages/F6801559-01.jpg

As it stands you need to remove the CR2032 from the board ASAP and replace it with a LR2032 rechargeable or a regular barrel 3.6v rechargeable - otherwise the CR2032 will overheat and leak / explode.

kanecvr wrote:

The problem is the barrel batteries are rechargeable - installing a regular lithium battery instead of a rechargeable is asking […]
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konc wrote:

einr wrote:

...or because a 3V CR2032 is not enough voltage (original battery is a 3.6V lithium barrel)

I've never encountered a single board that can't keep it's settings when fed with 3V instead of 3.6, so I wouldn't worry about that.

The problem is the barrel batteries are rechargeable - installing a regular lithium battery instead of a rechargeable is asking for trouble... For coin cell rechargeable 3.6v you should look for LR2032 (not CR2032) - but it's more expensive then a regular 3.6v barrel. What I like to do is remove the barrel batts and use 1 hole round pin sockets in place so I can stick a barrel battery in place for boards that I use, and remove the battery from the pin sockets when I'm not using the machine for longer periods of time to prevent leakage.

More specifically I use these: http://uk.rs-online.com/largeimages/F6801559-01.jpg

As it stands you need to remove the CR2032 from the board ASAP and replace it with a LR2032 rechargeable or a regular barrel 3.6v rechargeable - otherwise the CR2032 will overheat and leak / explode.

But this is a lithium barrel battery, not the more common NiCd/NiMH variant. Lithium 3.6V batteries aren't rechargeable, right?

kanecvr wrote:

konc wrote:

einr wrote:

...or because a 3V CR2032 is not enough voltage (original battery is a 3.6V lithium barrel)

I've never encountered a single board that can't keep it's settings when fed with 3V instead of 3.6, so I wouldn't worry about that.

The problem is the barrel batteries are rechargeable

Are batteries meant to be connected to the external battery connector still getting any charge? I always thought that they aren't. I cannot support/generalize this, but I've followed traces on one (yes, only one) motherboard from which I drew this conclusion.

Of course what you're saying about replacing a rechargeable battery on its original location is 100% a no-go.

Please don't suggest the LR2032 as a replacemnet for 3.6V NiCd - the charging voltage of max. 4.2V will be exceeded.

Most motherboards from that era had an external battery connector, but in most cases, it was meant to connect a non rechargeable battery "pack", in the event that the barrel battery stopped functioning.
However, I do have an old 386SX motherboard that has two external connectors (one for rechargeable and the other one for non rechargeable battery "packs").

"Newer" motherboards seem to work fine with 3 x 1.5V = 4.5V (I must admit, I've never tried only 3V), but older motherboards might require up to 6V (4 x 1.5V) to keep all the settings.

If your motherboard already has the coin cell connector, then it is easy to just replace it with another one, once the old one stops functioning (the BIOS will usually warn you if the battery is starting to fail).
Here's a link to a webpage that provides a number of options available in replacing CMOS batteries: http://pc-restorer.com/replacing-cmos-batteries-in-old-pcs

I actually came by one board which could not keep time and date settings because due to low voltage it ran slowly. Octec Hippo OP. I had to buy new barrel battery and solder it on extension cable so when it leaks (it surely will in twenty years or so), it doesn't do any damage to the board.

If you find this usefull, then this is how I have replaced both internal and external batteries on two of my systems.
Both batteries were 3.6volt ones. I have added both a picture of the two batteries and an eBay link for you.

The internal battery was replaced on a 486 motherboard. Actually. I soldered in a battery as the board arrived without.
The original internal battery, was however one of those barrel type ones. The battery is not heating up, and it is
still working without any issues, after some 60+ hours of computing.

The external battery was a replacement that I did. I used the original cables and soldered it to the one on the new
battery that arrived with wires allready soldered on.

Internal battery on eBay:
http://www.ebay.com/itm/New-LIR2032-Li-ion-3- … 4MAAOSwpDdVGVUE

External battery on eBay:
http://www.ebay.com/itm/New-Tekcell-SB-AA02-L … LIAAOSwgk1XF0gE

Well, thanks to all who replied. You are all quite helpful 😀

Anyway, I flipped the connector around. The system has been off and disconnected from the mains for many hours now and it seems to remember time and settings so I'm tentatively calling this a success. 😀

To clarify, there never has been a rechargeable battery of any kind in this computer. It has a ½AA 3.6V Lithium battery soldered to the motherboard. It looks kind of like the rechargeable NiCd kind that leaks all over the motherboard but is not one. It's functionally equivalent to a lithium CR2032 except for being slightly higher voltage and vastly more annoying to replace. So I'm happy there even was a header!

@brostenen, that looks good. Thanks. You can see my worse-looking solution in my specs thread:

The Brick 486DX

That is the first thing I did when I tried to revive an old 486 board a couple of years ago - solder in a coin cell battery holder. So I did, then I put in a cr2032. It worked fine for a couple of days, but then while playing lemmings I herd a loud POP and the computer froze. The CR2032 exploded. I took out my voldmeter and noticed the motherboard was supplying 4.6v to the contacts were the barrel battery was soldered (and where I soldered the coin cell battery holder).

I've seen rechargeable soldered 3.6v coin cell batteries like the one brostenen posted - but be warned - those leak as well - and since one surface is so close to the MB, I consider them more dangerous then barrels. They're also more expensive.

h-a-l-9000 wrote:

Please don't suggest the LR2032 as a replacemnet for 3.6V NiCd - the charging voltage of max. 4.2V will be exceeded.

I measured 4v on two boards (Soyo 386 board and gemlight 486 board - even tough the manual specifies 6v) - so it should be safe. It's best to check with a volt-meter to be safe. If it's over 4v, don't use an LR2032.

jesolo wrote:

Most motherboards from that era had an external battery connector, but in most cases, it was meant to connect a non rechargeable battery "pack", in the event that the barrel battery stopped

Curious. My gemlight 486sps103 is providing 4v trought pins 1 and 4 of the external battery connector.

@einr -if the board came with an external battery only, you need to use one of those. Generally pin 4 is negative and pin 1 si positive (connect red cable side). Pin 1 should be silk-screened right next to the connector. Try finding a manual online to see if it provides power to the external battery - or better - a volt-meter.

kanecvr wrote:

@einr -if the board came with an external battery only, you need to use one of those. Generally pin 4 is negative and pin 1 si positive (connect red cable side). Pin 1 should be silk-screened right next to the connector. Try finding a manual online to see if it provides power to the external battery - or better - a volt-meter.

The original battery was soldered to the board, and there's a header for an external battery nearby:

There is no complete manual for this board online as far as I can tell. TH99 had the header descriptions but no pinouts/polarity.

But now the computer has been left overnight since I flipped the connector and it still remembers the settings so this is looking pretty good 😀

You can always check for ground pin with a voltmeter - above picture (Table 17) shows it's on the opposite side of 6V and then just connect accordingly.