using rare earth magnets with 18650

I have a few unprotected 18650 batteries that i would like to use.I have searched the forums but would like a little conformation. I herd someone say they used magnets on their positive side of the battery to allow them to work in flashlights that have no spring.I personally dont see a problem with this but thought i should ask.Also (this i have not checked) is there commercial lights that take 18650 battery that do not have low voltage shut off protection ? Some manufactures state it and some do not??? thanks

If they wont make contact in my flashlight, i put a blob of solder on the battery.

I'm curious on how are you going to solder on steel contacts, cells typically can't be soldered per se, may have to spotweld a blob

superglue to keep the magnet from slipping if dropped (and possibly causing a short) seems to be popular here, too

I just use a dremel and grind a little area, then put the blob on. Oldest batteries with solder blobs i got is over 10 years old... The "blob" is still hanging in there. Works like a charm.

I was in the same situation. I ordered some rare earth magnets from BangGood. They were advertised specifically for adding contacts on Li-Ion cells, and are supposedly from Keeppower. I put one on one of the cells, then dropped it on its side from four feet and it didn't budge at all. For those interested they are round, and measure 5mm diameter and 3mm high.

http://www.rtdvapor.com/flat-top-battery-adapter/

De nada.

Chris

I think a lot of people have used magnets in a pinch to extend cells. I know I have - but I've only done it for testing until I could come up with a better/safer option.

I just don't have enough faith in a magnet holding if the flashlight drops or is hit just so with just the right force. What about the person who decides to use this setup in a light that just happens to be made of a material that is magnetic? The attraction when installing and screwing the light together could cause a magnet slip. I wouldn't want to risk and internal short. Maybe it would never happen, maybe the magnet it safe, but I don't want to be the one to find out otherwise.

Also - I would recommend against superglue. There is a component in superglue that can gas out if the temperature gets too high. The gas can potentially cause damage to the coating on reflectors.

The one CG linked to above seems like a safe option.
These custom one by Oveready are also a very good option - http://www.oveready.com/battery-/sleeves-spacers/delrin-battery-spacers-16/18mm-/prod_217.html - I use these myself with custom drop-ins where the springs aren't long enough to reach the battery.

I find it ironic that there is so much discussion and fear related to the use of LiIon cells here on CPF, yet some are so willing to toss a loose piece of metal inside a tube with a battery. Visions of pipe bombs are dancing in my head right now - kinda scary to me.

jorn said:

I just use a dremel and grind a little area, then put the blob on. Oldest batteries with solder blobs i got is over 10 years old... The "blob" is still hanging in there. Works like a charm.

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I need to try this, I didn't know solder will hold. I wonder if the steel is plated with something, like nickel, in which you managed to buzz off. Thanks for the heads up! I have a few dead or dying old 18650s, I can always recycle them if unsuccessful

I'm glad that SOYCD wrote all that out, so that I don't have to .... Usually whenever I post about the dangers of using magnets, I get a lot of (sometimes angry) pushback :sigh:

archimedes said:

I'm glad that SOYCD wrote all that out, so that I don't have to .... Usually whenever I post about the dangers of using magnets, I get a lot of (sometimes angry) pushback :sigh:

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To be fair, the gene pool needs to be flushed out from time to time.

Darwin for the win!

Chris

ChrisGarrett said:

http://www.rtdvapor.com/flat-top-battery-adapter/

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How would one hold that in place? Just drop it in before putting the cell in? That would probably work for cells in parallel, but what about cells in series.

Timothybil said:

How would one hold that in place? Just drop it in before putting the cell in? That would probably work for cells in parallel, but what about cells in series.

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One is obviously using that in a tube and the dimensions need to be close--the diameter of the disc and the diameter of the tube.

Another issue is how tall is that rivet and can you smash it down any, since it's brass?

Third, we're not just talking about the forward battery making contact with the pill, but the two batteries making contact with each other, which could be equally problematic.

If you have to use two of these spacers, say one for the forward battery>pill and one for the two cells in series, then you have two of those in there and you better have some wiggle room.

You'd have to carefully drop it down against the pill/driver, drop the cell in, then add a second one if needed.

Still, probably not a bad idea.

I made a crude one for my ShiningBeam I-Mini, with reverse polarity, to use with my naked Sanyo UR14500Ps, but went back to the button top 16340s.

Chris

On to the light that is going to be used with flat tops, does it have physical polarity protection (around the +)
. Maybe options of removing if plastic(of course care needs to be taken that the cell is the correct way). I have snipped the plastic ring off my Sportac so I can use flat tops as an example. Maybe soldering a spring on the + end of the light (if head can be removed for easy access) is easier that risking with the cells. Tbh if I plan on heavy use for the light, sometimes it's just easier to buy the right cells for it! Use the flat tops in another device that is fine for them . Only time I use a magnet is to space the cells that are already button tops by a couple of mm between cells . Not ideal and used with caution and regular checks . (Every use tbh but it's not an actual edc light).

That's fine until you get sent the wrong cells. I participated in a group buy of a special run of Samsung INR18650-30Q cells that had a button added. Unfortunately, there was an inventory mix-up by the shipping department, and a bunch of us got flat top cells instead. The vendor offered to replace the flat tops with the correct button tops, but we would have to ship the cells back to China. If you have looked at the current regulations concerning shipping Li-Ion cells, it was not worth the hassle. I will live with the flat tops and added magnets. All of my testing so far has not moved the magnets a single mm from where I placed them. That includes dropping them from about 1 meter unto the floor. Even if the magnets did slide, there is no chance of them shorting against the case since the 30Q flat top has a slight lip on the end from where the wrapper curves around over the edge. That would keep the magnet from touching the light's body if it slid that far.
[h=1]Samsung INR18650-30Q[/h]

I think the OR spacers are a little more secure in that you can get them in either 16 or 18mm widths. They also have some height to them which allows you to slide them down a tube safely without spinning sideways. I've taken a saw to some longer ones I have to trim them to just the right length for certain applications. I've gone as thin as about 3 mm. A little of the delrin can be easily removed from the end if you need more of a protrusion bump for contact.

thanks for all the info.good to know.
mike

archimedes said:

I'm glad that SOYCD wrote all that out, so that I don't have to .... Usually whenever I post about the dangers of using magnets, I get a lot of (sometimes angry) pushback :sigh:

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They can be fine. Depends on the application. If you are using them to extend the + end of a flat top cell, where there is no - contact near it, then it should be fine.

Illum said:

I need to try this, I didn't know solder will hold. I wonder if the steel is plated with something, like nickel, in which you managed to buzz off. Thanks for the heads up! I have a few dead or dying old 18650s, I can always recycle them if unsuccessful

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You can solder cells, same principle as normal soldering.

Very good video covering soldering here:

Illum said:

I need to try this, I didn't know solder will hold. I wonder if the steel is plated with something, like nickel, in which you managed to buzz off. Thanks for the heads up! I have a few dead or dying old 18650s, I can always recycle them if unsuccessful

Click to expand...

I've soldered nimh flat top batteries I got from packs with blobs and on some 4/5AAs I soldered brass screws on them that were cut off to make them AA length. I haven't soldered 18650 batteries though and am hesitant to even try for all the warnings folks have made about the heat damaging the batteries or worse. The trick to soldering batteries for me was having a larger iron (pistol grip even) and preclean the tops to make them shiny either grinding or sanding them then heating up the iron to get it hot before you even touch the battery and feed solder immediately. Have a wet sponge or even an ice cube ready to cool the battery off quickly after you are done.

What I think would work is some sort of non metal flat washer with a hole in it that you can glue a magnet into it would have to be either squishable or the right thickness to work in lights expecting button top cells. The magnet would hold the washer on the battery top and the washer would keep the magnet positioned properly inside lights on the top of the battery.