Add button to flat-top cells?

14 posts / 0 new
Last post
Ubehebe
Offline
Last seen: 7 years 3 months ago
Joined: 06/28/2012 - 01:14
Posts: 882
Location: Death Valley, Calif.
Add button to flat-top cells?

Anyone know what to use as a button to solder or otherwise attach to the positive terminal of flat-top 18650 batts?

I would like to use nonprotected li-ion batteries in several flashlights that do not have an internal spring in the flashlight battery compartment. Since flat-tops are flat-tops, they don’t work in springless batt compartments, no surprise there, because they can’t make contact. I could ADD a spring to the battery compartments of several lights, but a few would be really hard to mod this way because the way the internals are set up. Besides it seems to make more sense to mod the flat-top 18650s with some kind of button so they work in every flashlight.

Yes, I know the trick of using a little button magnet on the flat-top batt’s pos pole, and it works great, BUT in some decidedly nontechnical tests, I found that by tapping the battery on the side against a table, I could eventually move the magnet so that it would contact the flashlight barrel, which would create an uncontrolled short in an unprotected cell, something we all like to avoid Wink

I am pretty good with a soldering pen as I own an audio cable company and spend hours every day soldering all manner of electric stuff. BUT I know from personal experience with batteries that a FAST light touch is needed when soldering anything to a battery. I have soldered leads to batteries in non-flashlight projects only to find that just a few secs from a soldering iron zapped the battery dead. I don’t know the technical reasons why this happens, but it does. Not all the time, but enough to be a concern.

So buttons would be best if they were hollow so they heated fast and cooled quickly so the soldering pen doesn’t zap the battery, although I haven’t had any experience soldering li-ion battery poles.

What could I use for buttons? Or is there another way to make a button-top from a flat-top? There has to be a simple solution to this that many people are doing every day.

Thanks for any help you can give.

Ecig
Offline
Last seen: 9 years 1 month ago
Joined: 04/28/2012 - 22:37
Posts: 807
Location: Switzerland

Blob of solder.

First make a few cuts/scratches with knife, scalpel (exaxcto knife?) or something, on the surface where you would like to put a blob of solder, so that solder can attach to the surface more easily.
DOnt heat the surface of the cell for too long Smile

DARCANGEL
DARCANGEL's picture
Offline
Last seen: 6 months 4 days ago
Joined: 04/11/2012 - 00:06
Posts: 988
Location: the nickel city,New York

+1,I have used the blob-o-solder trick too.

Ubehebe
Offline
Last seen: 7 years 3 months ago
Joined: 06/28/2012 - 01:14
Posts: 882
Location: Death Valley, Calif.

Yeah, I was thinking of the blob-o-solder trick, although I was looking for something more elegant. But the easiest is usually the best!

Thanks for the tip. Since I have never done this before, it’s great to have such a dedicated group like BLF and their pooled knowledge. So much better than trying this and trying that.

Have to be quick to not toast the batt. I take it you didn’t have any probs with dead or crippled cells after attaching ye olde blobbo?

DARCANGEL
DARCANGEL's picture
Offline
Last seen: 6 months 4 days ago
Joined: 04/11/2012 - 00:06
Posts: 988
Location: the nickel city,New York

Nah,no problems,your only other alternative would be cut the wrapper and re-shrink a new one,probably not cost effective unless you do a large amount of them.

allthumbs
Offline
Last seen: 5 years 5 months ago
Joined: 07/02/2012 - 19:20
Posts: 170
Location: Pennsylvania

Use a nylon washer. With the standard AW 1.6mm magnet it almost fits in a7/16 ×200 ×1/16
nylon washer Hillman part # 881537 available at Lowes if your in the US. A little work with a drill bit
gives you a press fit or a drop of super glue at the edges if you misjudge a little. Nylon washers are available
at any good hardware store and Home depot. Leef made these for sale for a short time before he quit manufacturing.
The magnet can still move a bit but can not touch the flashlight body.

JohnnyMac
JohnnyMac's picture
Offline
Last seen: 5 days 1 hour ago
Joined: 04/12/2011 - 16:03
Posts: 8867
Location: Eastern PA

I use a 1mm x 3mm magnet centered on the cell. I then place a bead of crazy glue gel aroung the base of the magnet to secure it. The hell stays where you put it and bleed under the magnet. It dries clear and looks like it came from the factory with a perfect button top.

edc
edc's picture
Offline
Last seen: 6 years 3 months ago
Joined: 01/16/2011 - 02:28
Posts: 3300
Location: NSW AUSTRALIA

A blob works for me but you must be quick. I use flux as well. I think it could be potentially dangerous thing to do.

 

http://i1193.photobucket.com/albums

Ubehebe
Offline
Last seen: 7 years 3 months ago
Joined: 06/28/2012 - 01:14
Posts: 882
Location: Death Valley, Calif.

Glued magnets and the washer solution —- GREAT ideas both. Thank you!!

I did like 8-10 cells with the solder blob. WORKS GREAT. I got a really regularly shaped blob and then squared off the top with a file. Not factory perfect but works great and looks pretty good too.

I didn’t do all my flat tops with the solder, hoping another solution would come along, which it did from Johnny Mac and Allthumbs! I’ll experiment with both. That magnet sliding into the light barrel just scares the bejesus outta me.

If I need batts, I’m going with flat tops for a while from known trusted dealers, if there really is such a thing in China, which pains me to say that.

I just got 10 pairs of TFFs yesterday and today — from trusted ebay and web site vendors. HALF are fakes and won’t work in my HD 2010, Ke-5, sipik sk98 and others. They shut the circuit down if you try to go to high on the light. The other TFFs work fine and of course the flat-tops ALWAYS work fine.

I’m going to save my good protected batts for my 2-cell lights and go with the GOOD sanyo, panny, sony and Samsung flat-tops until the current bad TFFs clear out — if that ever happens.

BTW, the bad ones (from 2 different vendors) ALL were missing the hologram on the outside cello wrap and ALL had very little of the TF label holding the bottom neg plate on. But they DID have the hologram letters on the labels, so much for that stopping counterfeiting.

The good ones ALL had the cello wrap hologram and had MUCH more overlap by the label on the buttom. Also, the fakes were much longer than “normal” TFFs. But no way you can tell what the vendor will send you, so that info does nothing to assure that you’ll get real TFFs.

Ubehebe
Offline
Last seen: 7 years 3 months ago
Joined: 06/28/2012 - 01:14
Posts: 882
Location: Death Valley, Calif.

>>>>>>A blob works for me but you must be quick.

Yup, quick is the key. I sanded the top a bit and then got a good glob on my weller etcpt soldering stylus, which really holds the temp as it’s a soldering station meant for assembly-line apps rather than a hobby-grade standalone soldering pen.

I then quickly transferred the blob in an eye-blink without preheating the flattop. No pre-heating is a soldering no-no (because of cold-joint risk), but I tried a few and it works okay because the blob is big enough to preheat the batt top a little I guess.

I don’t think you would want to do this regularly with a little 15-watt Radio shack soldering pen, which is slow but usually okay for hobby soldering. I don’t think it would be hot enough for a blob.

Thanks for the pointers!!!

allthumbs
Offline
Last seen: 5 years 5 months ago
Joined: 07/02/2012 - 19:20
Posts: 170
Location: Pennsylvania

I like being able to easily remove the magnet, but I like JonnyMac`s idea so If your interested in
conducting a little experiment? Take a piece of clear cellophane tape lay it flat and stick the magnet
in the middle, then outline it with a bead of superglue gel. Let it dry then remove tape.

Old-Lumens
Old-Lumens's picture
Offline
Last seen: 5 years 1 month ago
Joined: 11/04/2011 - 11:39
Posts: 7478
Location: Tyler, TX, USA

If you want something fancier take these and solder them on the batteries.

Pre-tin the disc, pre-tin the battery, sit the disc on the battery and touch the cleaned soldering tip to the top of the disc, till the solder in between melts. Clean off the top with steel wool. Conducts good, won't come off and looks great.

 

My PayPal address: oldlumens (insert the @ sign here) gmail.com

My YouTube Flashlight Video Channel

The BLF Modding Links Thread 

http://imageshack.com/a/img922/1374/jQ2wdL.jpg

 

Ubehebe
Offline
Last seen: 7 years 3 months ago
Joined: 06/28/2012 - 01:14
Posts: 882
Location: Death Valley, Calif.

>>>>>Pre-tin the disc, pre-tin the battery, sit the disc on the battery and touch the cleaned soldering tip to the top of the disc,

Another great idea. Thank you. I am so glad I asked. I only came up with one idea by myself!!

This one (and the glued magnet variations) probably will look the best and you cannot beat copper for conductivity. Nothing is more conductive, except for silver. But the diff between silver and copper conductivity is so tiny that — to me — it’s not even worth worrying about.

Thanks again!

texaspyro
Offline
Last seen: 2 years 6 months ago
Joined: 04/29/2011 - 12:43
Posts: 4593

I built my own battery tab spot welder (one of the most sophisto units out there, commercial or otherwise) and use it to blast a button made of nickel rod onto the cell. Your local battery store could probably do this for you. Or have them use a strip of battery tab material and fold it into a button. Then maybe solder it so it does not unfold. Should cause less stress to the cell than soldering directly.

My welder:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=570#p280216

A very good CD welder development blog (occasionally down for updating):
http://www.turtlesarehere.com/html/cd_welder.html