need insight into CMOS battery replacement/repair on small motherboard

hi guys.. I'm new here, please forgive me if I am posting this in the wrong subforum.

I have done some computer hardware repair over the years but i don't solder (yet) nor do i have a great understanding of basic circuit board stuff.

I have a question to do with a tiny old blackberry motherboard and a tiny CMOS battery. a working CMOS battery is required for the phone's BIOS to boot and the phone to start.

If you know of a more appropriate forum besides edaboard, or a better subforum on edaboard, for me to additionally/alternately ask this question in, I am all ears for suggestions!

here are two pics of the motherboard from this old blackberry.

https://i.imgur.com/ld9FaXw.jpg


https://i.imgur.com/yom772y.jpg

(I tried to insert the images above in-line but they were too large to have the CMOS be visible in my post!)

here is a closeup up of the CMOS battery both in place, and after removal (to view the underside of the battery please click through to the links above):





if anyone cares its a bold 9930. the issue is I need to replace the CMOS battery (most importantly on another unit, this was a scrap unit i bought to see if i could achieve this repair before trying it on the unit i am hoping to save the data from).

the cmos battery I removed is sitting next to the motherboard. As you can see, it was held in place by this small metal bracket that appears to have been welded onto it.

the only difference between pic 1 and pic 2 is i have flipped the tiny CMOS battery over in the second one so you can see both sides of it.

getting the battery off required pretty hard prying, and getting off of the metal bracket (which broke off the mother board - you can see the little triangle of metal that remains attached to the motherboard) where it's welded on to the top of the battery seems very difficult with the tools i have on hand..

any thoughts?

thank you in advance

Hi,

Is the battery corroded? It looks so at first glance. That may be why it was hard to slide out/was stuck to the holder. Is that the practice board or the actual board? Maybe that last point doesn't matter at all.

I'd clean the battery holder broken off piece with a very gentle filing, a fine small metal file if you have one or sandpaper for metal. Then wash and dry to check it's clean.

From what I can see, and it's guessing a bit as the photo is small, that part needs to be soldered back on. So, ideally the old solder would be removed, easy enough to do with a cheap suction tool. If you have taken the plunge and got a soldering iron, you can practice doing a few cheap resistors on a piece of cheap veroboard (some people call it that) before doing the solder joint for the battery holder.

It's a lot easier than it looks. I think you want to solder the triangle bit of the battery holder to the solder triangle on the board. At a push, a not nice push, hold the battery holder in place with pliers and use something to heat the solder and battery holder bit and hope it gets hot enough to melt and weld together again.

If the problem is different, best get a second opinion.

The bracket appears to be spot-welded to the battery. Do not solder anything to the small battery, since the high heat no doubt shortens its life.

You may succeed at soldering a bracket onto the triangle. The triangle needs to be solidly attached to the board. The bracket needs to have a bit of springy force in it, to hold the battery to the metal contact.

If it were me I would drill tiny holes in the board. Feed wire through the holes. One hole contacting the small triangle, so you can solder a wire to it. Another hole at the opposite diameter of the battery.
Wrap a wire loop around the battery to firmly hold it to the board. 18 or 20 gauge is suitable. Strip away insulation so that bare copper touches the battery. Twist or bend the wire ends.

Hi BradtheRad, thanks for taking the time to write me back. You are right, it is was spot welded. If you were able to click through to the larger images , and the one that shows the underside of the battery, you can see that weirdly the three little spots went through to the underside of the old battery!

So.. I feel very out of my depth here, reading through yours and the other responders replies. I wonder if maybe I should find someone to do this job for me, but i feel a little overwhelmed about how to find that person. This is part one of a two part fix to get data off this device. The second part is replace the charging/data port that requires micro-soldering - that part I have located a pro / experience micro solder-er to do. But that person seemed skeptical about this cmos part of the job, which according to my research has to come first to get the device booting.

anyway - hmm, i'll ask some questions in-line with your response.. hope that's ok?

BradtheRad said:

The bracket appears to be spot-welded to the battery. Do not solder anything to the small battery, since the high heat no doubt shortens its life.

You may succeed at soldering a bracket onto the triangle. The triangle needs to be solidly attached to the board. The bracket needs to have a bit of springy force in it, to hold the battery to the metal contact.

Click to expand...

so.. the triangle.. do you mean the little bit that the bracket was previously attached to? here:

**broken link removed**

the "springy force" requirement makes sense.. I actually suspect the ability of a modified bracket to provide enough springy force -- after all , they spot welded it in there for a reason, right? But i wonder if there might be some sort of very sticky special tape that could work, if only as a temporary fix (long enough to get part 2 done and data off of it)?

BradtheRad said:

If it were me I would drill tiny holes in the board. Feed wire through the holes. One hole contacting the small triangle, so you can solder a wire to it. Another hole at the opposite diameter of the battery.
Wrap a wire loop around the battery to firmly hold it to the board. 18 or 20 gauge is suitable. Strip away insulation so that bare copper touches the battery. Twist or bend the wire ends.

Click to expand...

Could you show me somehow where exactly you would drill the holes? the wire plan sounds promising but .. i'm having a hard time following it without a drawing or something.

Another thought I've had is.. I don't really know where to get a replacement battery like this, i can't make out any marks on the battery but i could measure it and look for a silver oxide battery of the same size I suppose.

Well, thanks, again, a bunch!

d123 said:

Hi,

Is the battery corroded? It looks so at first glance. That may be why it was hard to slide out/was stuck to the holder.

Click to expand...

- the battery does appear corroded, but it was working enough for the phone I took it out of to boot successfully. It wasn't stuck do to corrosion, it was stuck to the bracket because it was spot welded to the bracket in three places

d123 said:

Is that the practice board or the actual board?

Click to expand...

the practice board is the one i removed the battery from.. i have 3 of these phones - aka practice boards - besides the one I'm trying to fix.

d123 said:

Maybe that last point doesn't matter at all.

I'd clean the battery holder broken off piece with a very gentle filing, a fine small metal file if you have one or sandpaper for metal. Then wash and dry to check it's clean.

From what I can see, and it's guessing a bit as the photo is small, that part needs to be soldered back on. So, ideally the old solder would be removed, easy enough to do with a cheap suction tool. If you have taken the plunge and got a soldering iron, you can practice doing a few cheap resistors on a piece of cheap veroboard (some people call it that) before doing the solder joint for the battery holder.

Click to expand...

it was never soldered on to begin with .. well, i suppose the bracket was soldered to the board where that tiny triangle was. but otherwise the battery was spot welded, from the top of the bracket and through the bracket, i'm guessing, onto the board. so while the bracket provided some of the work of holding the battery on there, the spot welding ensured it all stayed together

d123 said:

It's a lot easier than it looks. I think you want to solder the triangle bit of the battery holder to the solder triangle on the board. At a push, a not nice push, hold the battery holder in place with pliers and use something to heat the solder and battery holder bit and hope it gets hot enough to melt and weld together again.

Click to expand...

This part makes since - soldering triangle to triangle - i can imagine doing that.. or getting someone to do it. the tricky bit will be getting a replacement battery (because on the actual board i need to fix - not the practice ones - i will need to sub in a working battery in this step) to stick inside the bracket. Another user wrote as well below and I was thinking maybe some tape could be used a temp fix .. because i don't think spot welding it in as with the original will be within my skill set..


thanks so much, again!

- - - Updated - - -

oops - my attachment didn't work for some reason - there was supposed to be this image inserted inline above

Hi,

If the battery is about 2cm diameter, it may well be a CR2032, they are sold everywhere and are the standard battery on a computer motherboard. If it's smaller, like a watch battery, take it to a shop and see if they can figure out which of the button/coin cells it is. You can clean the corrosion off with the tip of a flat screwdriver or a knifeblade if you have no other tools, and I strongly recommend you clean the corrosion off, the battery should make good contact with the battery terminals.

I guess the battery is cold/spot-welded in place because if it's in a phone, it'll move around a lot and needs to be fixed in place.

Maybe even heating a screwdriver tip and pressing the triangle in place with it will work, and then install the new battery. As you seem more interested in the drilling idea, I'll leave that to Brad.

- - - Updated - - -

CMOS batteries on Wikipedia mentions CR2032 and CR2016.

- - - Updated - - -

and How to replace the CMOS battery, in case it's any use to you.

goldfish2909 said:

wonder if there might be some sort of very sticky special tape that could work, if only as a temporary fix (long enough to get part 2 done and data off of it)?

Click to expand...

Yes, a search turns up more options nowadays.

A few DIY'ers have tried mixing graphite and adhesive, to create electrically-conductive glue. Example:

https://www.instructables.com/id/Make-Conductive-Glue-and-Glue-a-Circuit/

There are commercial products. Try searching for Circuitwriter (or conductive adhesive) at Amazon and Ebay. Watch that you don't end up with brush-on electrical insulating compound.

You may find conductive tape with conductive adhesive at a local store.

CircuitWorks, mail order about $15. 'Liquid silver' which you apply from a tube. When dry it is like a weak glue which carries electricity.