External CMOS Battery -Voltages 3

[tasteegroove]

Hello all. I am working with an old 386 Biostar motherboard. I desoldered the 3.6V NiCad battery because it had corroded and I believed it to the cause of sudden lockups in the system. AFter the removal, the lockups ceased to happen and now i am in the process of attaching an external battery. The external battery jumper on the mobo is 4 pin, with pin 2 missing. I have a 4pin external battery that runs on 4 AA batterys, giving 6 volts. I have attached it for testing and it seems to work fine. I was curious as to wether leaving this battery on could cause problems in the long run, having different voltage than the previous battery. It seems to work fine now, but who knows in a few weeks, months. Any help greatly appreciated.

 

[edfair]

No problem with the voltage.
You would be better off to get one of the external batteries that are intended for the use, however. They give better life than the AA and don't have the potential corrosion problems.
Or you could bring 2 wires out of the holes on the M/B to an off board lithium. Saves you having to take the board out the next time 3 years or so down the road.

Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[paparazi]

I wouldn't be quite as possitive as edfair regarding this higher voltage. Personally I would fit some sort of rechargable battery but with a closer voltage to the original.
What concerns me is because the old battery was a NiCad type then there must be a built in recharge circuit
when the board is live, so non rechargeable battery types wouldn't be advisable.
I think a couple of low capacity 500ma or similar AA NiCads fitted into a cheap radio shack (Tandy) battery holder and the Pos/Neg wires soldered onto the motherboard, or even a couple of NiCad AA's with solder tags taped together and wires attached (initially pre charge) as the onboard charging circuit is likely to be of low charging capacity.
2 X 1.2 volt NiCads + 3.4 Volts, should be sufficient.
Martin


Replying helps further our knowledge, without comment leaves us wondering.

 

[edfair]

There was a recharge circuit. But is was on the soldered in battery which was connected to the external battery post by a jumper. The only way an external can hook up is by pulling the recharge and internal.
I've used the 2AA battery packs, which is the reason for the corrosion warning.


Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[pudda]

Nearly all cordless phone batteries are 3.6v and are rechargeable. Have used many for the older systems by charging them initially in a cordless phone (may have to splice the wires to the new battery to charge it) then attaching them with the external battery connector. I usually find the older style but new batteries at discount stores (Kmart, WalMart, Target, etc.) on sale for about 50 cents. Not much call for them anymore...

The test continues...