Safe to add solder, as a button-top, to a flat-top cell?

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DHart
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Safe to add solder, as a button-top, to a flat-top cell?

Is this safe? Is it possible?

I have a flat-top cell that I find doesn’t contact effectively as a button-top would.

brewster
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It has been done many times. Prep the surface well with a bit of sanding and some flux. Solder it quickly, so you don’t get the cell too hot. Paradoxically that requires a hot iron.

I find the solder blob is better than a button top, because the resistance is lower.

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You can get some really low melting-temperature solders also, such as Rose’s metal. Prep and flux as mentioned is always best for any soldering.

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I like to cut a small disk out of sheet copper. I then apply solder paste between the disk and the top of the battery.

Place the battery face-up in a vise. Use a toothpick to hold down the copper disk. Then apply a hot soldering iron to the top of the disk.

Observe the solder paste at the edges of the disk carefully. The instant it melts and turns silver remove the soldering iron.

When it cools, take a file and briefly run it over the top of the copper disk to remove any solder from the tip of the iron.

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Done it many times myself. They tend to oxidize and need cleaning now and then. But works quite well.

arek98
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Magnets suck, they move, use solder, use lower temp solder if you want, regular is still ok, just prep surface, use flux and do it quickly. If solder does not stick at first, wait a bit to let it cool, clean battery contact from whatever left from failed attempt, scrap it more, put fresh flux and try again.

FlashKat
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Just buy a new button top battery.

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Magnets have to be once of the worse ideas possible with lights like the Q8 and LT where screwing the head down is virtually guaranteed to move them around.

Solder blobs are easy to do and with a little practice only takes a few seconds to add. I don’t even bother sanding the surface and I’ve never been able to pull one off or move it even with pliers.

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Doing a solder blob was game changing . There are lots of threads on BLF on how -to . The trick is rough up top of the cell /Clean it ..add flux ..add lots of solder to the soldering iron. It happens in under two second ds so you're not heating up the cell at all.

 Magnets move around /dent cells and are much more dangerous .

 Grab some recycled cordless drill packs or laptop packs out of the recycling bins to experiment on if you're really worried .

But expect to have one of those "why the hell didn't I try this earlier moments "

 I've had at least 4 of them .

 1# solder blobs 

 2# high cri emitters 

 3# diffusion film 

 4# minus Green filters 

....four simple things that make a big difference .

Flux .... flux... and more flux 

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DHart
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Wonderful, guys! Thank you all for the comments and tips.

And, @Boaz I’m with you on the “why the hell didn’t I try this earlier moments” and wish to add one more:

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Boaz wrote:

 Magnets move around /dent cells and are much more dangerous .


I’ve had a short inside battery pack due to a moved magnet. I strongly recommend against this method.
Low temperature solder is the easiest safe way of adding a button top.
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FlashKat wrote:

Just buy a new button top battery.

That would be my advice as well.

I don't solder, and I'm not a fan of the magnet solution.  :-)

DHart
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Of course the easy answer is just buy some button-top cells. And nothing wrong with that option. But…

Facts are… I have done a LOT of soldering on my guitar electronics; I have the tools, flux, and solder; and… I have a couple of brand-new VapCell flat-top 10440 cells that I wouldn’t mind having a bit of a button on!

SO… why the heck, not, pop a bit of solder on top?

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Sand the top, use flux, heat up iron a lot and use a wide tip, apply solder quickly by rubbing the solder on the cell with the iron tip and remove the iron asap.

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yes that works, it can be hard to solder quickly to the steel though. maybe practice on some old cell you don;t care about.

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Definitively. Flux may leave slight rust marks on the cell, but nothing major.

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