System Battery Dead on a 486

Zenith data systems / 150-0824-p2
September 20, 2010 at 19:02:03
Specs: DOS 6.22, 486SX 66MHz/ 4MB EDO
I recently bought an unidentified Zenith 486 motherboard for kicks; I'd like to run the original Mechwarrior without an emulator. I turned it on and got the ever popular "System Battery is Dead" message at POST. I'm used to working with CR2032 batteries that pop right out, but this one is a BR1225 3 volt that appears to be soldered onto the contact pins.

I've read some old posts about attaching an external battery, but I'm not sure how I would go about that. There are replacement batteries out there like this one: http://www.batterymart.com/p-lith-2...
which appear to require de/resoldering. What's the best way to go?


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#1
September 20, 2010 at 19:54:09
Sometimes they would spot weld metal contacts to the battery and then that piece would be soldered to the motherboard. Because of that it might be hard to find an exact replacement. A place like Batteries Plus could probably make one but it'd probably be better if you jury-rigged one up yourself.

In the past I've gone to Radio Shack and gotten a 2, 3 or 4 AA sized battery holder (whatever would match the original voltage) and solder the leads to the motherboard. Then buy some AA nicads, lithium or alkaline batteries (again whatever type matched the original) and use them. In your case you'd want a 2 cell holder and use lithium or alkaline AA.

Then use some double-sided foam tape or velcro and stick the holder at a convenient place inside the case.

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#2
September 20, 2010 at 20:30:26
Thanks for the quick reply!
Sorry for my link fail, it's in the OP now. That battery looks exactly like the assembly on the motherboard:
http://www.flickr.com/photos/333031...
To the left of J31 in the picture is the text "4.5V Alkaline". Would you have soldered the leads to where the battery was? What about attaching batteries through the jumper?

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#3
September 20, 2010 at 21:53:06
J31 is where you'd attach an external battery. Often those motherboard would have an on-board nicad rechargable battery. If you were using it you'd have the external connection jumpered as in the photo.

The external batteries would come with a 4-wire connector with one of the holes filled in to act as a key so it could only be installed one way. If you were using the external you'd remove the jumper which I guess would disable the on-board battery and then attach the external battery there.

Your motherboard has a lithium which is not a rechargable battery but I guess their logic is the same--with J31 jumpered you're using the on-board and with it off you attach the external one there. It's kind of odd the batteries have different voltages. I assume that's due to their different locations on the motherboard so the voltage measured at the cmos chip is the same regardless of which one you use.

I'm almost sure you can still buy those external batteries at Batteries Plus, a computer supply store or online. Or you could make one with a 3 cell holder. You could probably solder the holder leads to one of the 4-wire audio cables that come with a cdrom and attach it to the motherboard that way. You have to be careful of the polarity since the cdrom cables aren't usually keyed to fit one way. You could also cut the 4-wire speaker connection from an old case and use that.

I have some of those external batteries but they're probably dead by now but I could check the polarity if you decide to build one. But if it was me I'd just buy an external one. That way you know it's done right.

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Related Solutions

#4
September 20, 2010 at 22:10:28
I found this one on ebay:

http://cgi.ebay.com/Rayovac-Part-84...

Some of the connectors weren't keyed (with one of the holes filled in). I can't tell if that one is keyed or not. If not of course, you need to make sure you connect it right.

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#5
September 20, 2010 at 23:03:08
Already placed a bid :)
Pin 1 is hot, 4 is not, got it.
Thank you so much for your time Dave!

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#6
September 20, 2010 at 23:10:33
Good luck. I doubt you'll get any competing bids but if so, check other places too. You don't want to get in a bidding war for something you can get elsewhere.

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#7
September 24, 2010 at 20:56:39
Unfortunately, there is another bidder. I'd still like to get the Rayovac 840, but making my own battery sounds like a good idea, especially since that part has been out of production since mid-2009. I found this thread from 2007, look familiar?
http://www.computing.net/answers/ha...
A little more detail on the battery holder idea convinced me. That way I'd be able to easily replace the batteries when they died.
http://www.batteryspace.com/battery...
This holder caught my eye because it has a cover and the color-coded wires. No need to check the polarity there, right? I do have some of those old analog audio cables laying around, so I'll use that and block off the correct hole. A sound plan?

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#8
September 25, 2010 at 00:05:47
You might want to up your bid 50 cents or so just before the auction ends. Maybe you'll get lucky.

If not I can cut off the wires and connector on one of the bad batteries I have and mail it to you. You could solder them to the battery holder wires. That way the polarity wouldn't be in question.

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#9
October 7, 2010 at 12:36:55
Thanks Dave, no need though. I spliced the red and black battery leads into the corresponding wires on a 4 pin analog audio cable, and made a solder plug to artificially key the connector. The Zenith retains it's settings between boots, and no error message during post. Solved!

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#10
October 7, 2010 at 19:22:31
I'm glad it worked out. Thanks for posting back.

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