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Battery on a generic 386 system

Unknown_K

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On Friday I snagged a generic AMD 386/33 system to restore. The onboard battery was starting to leak (like normal, was dead) so I removed it. I installed a coin battery holder and 3V coin battery in its place. I was under the assumption those (stock) are not rechargable batteries (like in an Amiga where they have 3 legs). Well I heard some noise running that system today, got a battery is low from the machine on a reboot, and decided to look at it. Battery was still intact but was reading 4VDC, new batteries might read up to 3.3V but not 4V. Is that board trying to charge up the battery?

Anybody else experience this?
 
It certainly sounds like it.
If the original battery was barrel shaped, you can be very certain that the battery was a rechargeable.
 
If it's not a coin cell that's soldered down, it's probably a rechargeable. You can use 3 or 4 AA cells (or similar configuration), but install a diode (a 1N4002 will work fine) to prevent the mobo from trying to charge a non-rechargeable battery. Trying to charge a lithium coin cell can result in a nasty surprise.

Some motherboards also have a 3 pin (4 with one removed) header to attach a non-rechargeable battery.
 
Trying to charge a lithium coin cell can result in a nasty surprise..

Yup... like the liquid in the battery leaking out and corroding everything it touches.

OR, if the battery reaches about 340 degrees inside it has a self sustaining reaction. This isn't so bad when you have 1 battery cell, it tends to pop, sometimes flaming when it does. Where it's bad is if you have a laptop battery with 9 cells. You'll have lots of smoke, flame, and fire plus the explosions when the batteries go POW. And it's not a small pop either.

http://www.youtube.com/watch?v=gcd34tt8YPU
 
Sooo,wouldn't a rechargeable Lithium Coin Cell work ok?I put one of those in my Tandy 100 with no issues.(Well,none yet anyway)
cgrape2
 
I think Doug's talking about the memory backup battery.

Ah, okay. Well since the coin cell isn't a rechargeable as original equipment, you'll be okay. The danger to avoid is charging a non-rechargeable battery. Putting a rechargeable in a non-rechargeable holder is okay.
 
Ah, okay. Well since the coin cell isn't a rechargeable as original equipment, you'll be okay. The danger to avoid is charging a non-rechargeable battery. Putting a rechargeable in a non-rechargeable holder is okay.
Ah, no, the M100 normally uses a standard 3-button rechargeable NiCd as used in your typical 386 & 486 (often by Varta), but if Doug says his Lithium coin is rechargeable then he should be OK. I prefer to use the small cordless phone batteries myself.
 
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