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Replacing soldered CMOS battery on 486 computer

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First post, by yomarz

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I have been trying to restore this Packard Bell Axcel 46CD computer for my friend, but I've been struggling because I have never worked on a 486 before. It boots to BIOS, but the roadblock that I'm at now is that the battery is dead, but it's not an easily removable CR2032 like I'm used to. It's a BR1225 3V that appears to be soldered in place.

https://i.imgur.com/R4HNos4.jpg
The bent end is from me attempting to lift that top metal piece before I realized it was all connected.

What are my options for replacing the battery? I do not have a soldering iron nor any soldering experience, but I may be willing if that's the only option. I was also reading other threads where people had similar issues, and they proposed the use of external batteries like the Rayovac 840 battery pack which would be connected to pins labeled EXT BATT or something like that, but I couldn't find anything like that on this board. In this thread https://www.computing.net/answers/hardware/sy … -486/69738.html they claim that the pins labeled J31 are where the external battery should be attached, and I found J31 on my board, but I don't know if this is a solution specific to this person's computer. Also, I don't know which pins in this cluster are actually J31.

https://i.imgur.com/A0Rhc37.jpg
https://i.imgur.com/oP4tmDc.jpg

Any help would be greatly appreciated. I'm used to Pentium systems and later that are more similar to modern computers, so this stuff is pretty alien to me.

Pics of the board:
https://i.imgur.com/2cOYkN4.jpg
https://i.imgur.com/jSBaBrj.jpg
https://i.imgur.com/aMSvcDA.jpg
https://i.imgur.com/3Dm4QEH.jpg
https://i.imgur.com/Zek3cJK.jpg
https://i.imgur.com/w2m4qWd.jpg

Reply 1 of 2, by Deunan

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No offence but if you've never desoldered anything before I'd recommend you don't learn how to do that on that mobo. There's a very good chance you'll get the temperature wrong, or use too weak (or too powerful) soldering iron and cause more damage - like pull the via out or delaminate the pads. Same goes for any mechanical means, I mean you can try to cut that battery out but take extra care not to even scratch those traces that go under it. You cut one of them and the mobo will need to be repaired.

As for external battery connector, I'd say it's the one called Jbte next to the OPTi 82C602 chip. Most likely the jumper needs to be removed and the external battery should be connected to pins 1 (-) and 4 (+). But do check that with a meter first. 1 should be connected to GND, and 4 to mobo battery (+), except most likely through a diode. Pin 3 is connected to RTC or that OPTi chip maybe.

Reply 2 of 2, by DaveJustDave

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i just did one of these. put a dab of solder or flux on the underside. placed some solder wick between each solder joint (from the underside) and a hot iron and the battery practically fell out under its own weight, all traces and pad intact. i wired up a coin cell holder and a CR2032 battery and it worked great.

I have no clue what I'm doing! If you want to watch me fumble through all my retro projects, you can watch here: https://www.youtube.com/user/MrDavejustdave

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