Magnets for batteries

[j3bnl]

Looking for a source for magnets to fit onto my flat positive end of my 18650 batteries.
I need these to use the modded charger I am having made for me.

 

[DanielG]

http://www.dealextreme.com/details.dx/sku.3461
Rare-Earth Magnet (10-Pack 9 mm) Also Suitable for Extending 18650/CR123A Batteries $1.20

 

[j3bnl]

Cheers.
Just found these aswell http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=1414

Are these the same thing?

 

[DM51]

Here is a UK-based source for you. Neodymium magnets are the strongest. Weaker types could slip off the cell terminal and cause a short against the side of the light.

 

[j3bnl]

Here is a UK-based source for you. Neodymium magnets are the strongest. Weaker types could slip off the cell terminal and cause a short against the side of the light.

Cheers DM. :thumbsup:

Have emailed them and will see what they say.

Edit :- Got a reply to my email £50 ($100) minimum order!
Will look elsewhere I think.

 

[MiniLux]

Another source for neodymium magnets, shipping worldwide:

http://www.supermagnete.de/eng/index.php?switch_lang=1

 

[donn_]

I hope this doesn't sound like a thread hijacking, but I have some questions about charging and spacer magnets, and the thread title is perfect.

There seem to be lots of shapes and sizes for these things. Is there an optimum size, shape and strength for them?

Do the magnets with holes have any use, like fitting over the button of the cell?

Is there a theoretical limit to how may cells or magnets can be strung together, either in use or in charging? For example..I want to charge 3 Li-ion C cells at once, and my charger only holds 2. Can I string 3 together with magnets and charge them all at once with my universal smart charger? Or...can I use one cell in a two cell tube, and use magnets to fill the extra space?

 

[SilverFox]

Hello Donn,

The key is resistance. If your magnet connections don't introduce any additional resistance, you are good to go. However, chargers will see additional resistance as batteries that are less than healthy and may adjust the charge rate accordingly.

In series charging, you may end up with unbalanced cells because of the extra resistance introduced by the magnetic connection.

Keep in mind that Li-Ion cells have an internal resistance of around 0.1 - 0.3 ohms, so it doesn't take much resistance to throw things off.

Tom

 

[65535]

Fox brings up a very true issue, most neodymium magnets are covered in a chrome type hard oxidation resistant coating, not known for its low resistance. When charging it might be a better idea to use a copper spacer. If possible.

 

[DM51]

That's an excellent point from SilverFox.

I just tried measuring the resistance of a magnet, but I had difficulties because the probes on my DMM seem to be, er, well, magnetic, and they won't hold where I want them on this $!%#& magnet, lol.

I'm getting a reading of 0.4 Ω, FWIW. Surely that can't be right?

 

[j3bnl]

Have ordered some of these :-http://www.kaidomain.com/WEBUI/Produ...px?TranID=1414

I also have some coming from AW so will see what works best.
Thanks for all the advice. :thumbsup:

 

[Bullzeyebill]

I get mine from http://www.kjmagnetics.com/ Decent prices. Best selection on the web, I believe.

Bill

 

[cat]

Why do you need magnets on the + end of 18650 for that setup? Those chargers do AA, a similar diameter, and the + contacts are strips,.....?

 

[j3bnl]

Why do you need magnets on the + end of 18650 for that setup? Those chargers do AA, a similar diameter, and the + contacts are strips,.....?

Its not the Volcraft cradle that I'm getting Brian, its the other one which requires magnets if the batteries have a flat positive end.
This is according to the guy who is modding it (he has just finished it) so I will bow to his knowledge and experience on this subject and if he says it needs them it needs them.:thumbsup:
The ones from Kai only cost $0.99 so its not like it cost a lot of money and AW has kindly offered some too so will let you know when it arrives if it did indeed require them.

 

[j3bnl]

Cat you have a pm

 

[cat]

ohhh, ok. I must check out the photos again. The flat top. And magnets would be more stable then spacers there.


heyy, your sig line seems to be changing - I don't remember seeing that Tri-Seoul there before. And 2 asphericals?

 

[j3bnl]

ohhh, ok. I must check out the photos again. The flat top. And magnets would be more stable then spacers there.


heyy, your sig line seems to be changing - I don't remember seeing that Tri-Seoul there before. And 2 asphericals?

The magnet would only be required on batteries with flat positive ends. The ones with button tops are fine, like AW's C cells and 17670's etc.
I have difficulty keeping up with my lights myself, are you after an aspherical?

 

[Vikas Sontakke]

Do you really want a powerful magnet touching the converter board? There normally is an inductor on the board and it probably does not like being so close to a magnet.

- Vikas

 

[cat]

In this case, the Li-ion charger is separate from the battery holder. Although the battery holder is a modifed NiMH charger, the NiMH charging circuit is not used.

 

[j3bnl]

In this case, the Li-ion charger is separate from the battery holder. Although the battery holder is a modifed NiMH charger, the NiMH charging circuit is not used.

Couldn't have put it better myself. :thumbsup: