# can i solder wires to magnets and attach magnets to battery for charging?



## waddup (Aug 14, 2009)

i have a triton charger (for model airplanes etc, charges everything nimh,lion pb,etc) id like to run the 2 wires out of it and on to 2 magnets that attach to any battery i need to charge +e -ve,

you guys solder the wire to the magnets? (or epoxy?)

what magnets ??

i did search but didnt find anything after 2007.


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## Mjolnir (Aug 14, 2009)

I know that people do solder rare earth magnets so wires for this purpose, but you have to be careful while soldering, since the heat from the soldering can destroy the magnetism of the magnet. However, I believe that if you do it fast enough, it can work fine.


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## Anders (Aug 14, 2009)

https://www.candlepowerforums.com/threads/222630

Anders


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## Justin Case (Aug 14, 2009)

That link mentions the Curie temp (Tcurie), which is the temp above which a ferromagnet loses its permanent magnetism. The figure of merit that you really need is the maximum operating temperature (Top), which is the point above which the magnet starts to degrade. If you reach Tcurie, it's already too late. For a standard N grade neodymium-iron-boron magnet, Top ~ 80C, while Tcurie ~ 310C. If you go with a higher grade NdFeB magnet like NEH, you can get a Top ~ 200C and Tcurie ~ 350C. That would make soldering a wire to the magnet quite easy with little risk of killing the magnetism.

I've successfully soldered to standard N grade NdFeB magnets, but you have to be quick to avoid overheating the magnet.


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## n3eg (Aug 14, 2009)

I've soldered to magnets removed from damaged speakers. The magnet housing usually is solderable, and I solder to the edge of it.

Of course, I'll try to solder anything that isn't steel, aluminum, magnesium, or beryllium oxide...


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## N10 (Aug 14, 2009)

wasn't there a folder somewhere warning about use of magnets with lithium ion batts? But i think it was during use in the flashlight and not charging..correct me if i'm wrong..


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## Anders (Aug 14, 2009)

Hello N10.

Yes, thats correct.

Earlier it was very common to use magnets as spacers, that was before the "Button Top Cell" hit the market.

It was very common to use it in Surefire U2 with the flat 18650, the earlier models of U2 with the wide battery tube.

A short circuit occurs if the magnet touch the battery tube.

Anders


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## clintb (Aug 15, 2009)

Here's a nice table illustrating what Justin was telling us.

http://www.stanfordmagnets.com/magnet.html#nfb


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## worldedit (Aug 15, 2009)

I got one of those:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9287
Put connectors on them and just squeeze the battery. Works good, with much less resistance than the magnets i used before. Rare earth magnets are pretty bad conductors.


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## tino_ale (Aug 16, 2009)

Have tried this before. No matter how fast I was for soldering, the magnet would loose part of it's strenght. The remaining strenght was sufficient though for the purpose of charging leads.

I am unsure about the resistivity of magnets, they may not be Ok for high current charging/discharging (like A123 system batts for example).


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## VidPro (Aug 16, 2009)

i used different ideas from the advice i got here. https://www.candlepowerforums.com/threads/227098&highlight=magnets

soldered direct, lost a LOT of magnetism, some more than others. these Were high strength neos nickle plated.
being larger magnets it was not easy to solder without getting a lot of heat. i assume smaller magnets would get one small part of it to temperature faster, so it would flow easier.
Some of them i got soldered, with less loss of magnetism, but when i did the Hard pull test (try and tear out the solder point) i discovered it had not achieved full flow and full intermingling of the metals, so on the hard pull test, the solder came loose.
---[]

I kept the ones that had the best of both worlds, least ammount of magnet loss, and still a great solder attachement.

then i used the idea of combining, i wanted a very strong soldered attachement, and a Very strong magnet attachement, and minimal chances of shorting.
so i soldered to 1, and Stuck (using magnatism) Stacked to the second one, that had not been heated, then wrapped the pair in heat shrink.
---[][]
also i made sure that i cleaned the contact points, between the magnets, to insure good magnet to magnet contact prior to wrapping it up , sorta ground them together, to insure large contact area.

also i discovered late, that polarity was very usefull in keeping the contacts from ever touching, you dont want them to rush across the table to connect to thier polar opposites.

the ones i made might be concidered a bit overboard , as it has about a 5 pound pull, but i wanted something that would be as good as a proper clamp or spring holder thing, and the thin battery connect points dont hold as well as a larger hunk of metal could, depending on the battery.


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## VidPro (Aug 16, 2009)

oops deleted


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## LuxLuthor (Aug 16, 2009)

tino_ale said:


> Have tried this before. No matter how fast I was for soldering, the magnet would loose part of it's strenght. The remaining strenght was sufficient though for the purpose of charging leads.
> 
> I am unsure about the resistivity of magnets, they may not be Ok for high current charging/discharging (like A123 system batts for example).



My set had 3 mΩ shown here.


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## Drewfus2101 (Aug 17, 2009)

I did a search online, and eventually found some school science experiment website that sold packs of 12" wires with a magnet soldered on each end. I bought a set and they seem to work good for all sorts of things. 

I have not checked the resistance yet though. I'll have to check that this week.


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## clintb (Aug 17, 2009)

Drewfus2101 said:


> I did a search online, and eventually found some school science experiment website that sold packs of 12" wires with a magnet soldered on each end. I bought a set and they seem to work good for all sorts of things.
> 
> I have not checked the resistance yet though. I'll have to check that this week.


Please to be sharing the website, sir.


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## TakeTheActive (Aug 17, 2009)

*Re: packs of 12" wires with a magnet soldered on each end*



clintb said:


> Please to be sharing the website, sir.



+1


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## tino_ale (Aug 18, 2009)

LuxLuthor said:


> My set had 3 mΩ shown here.


Good to know but I am still wondering about the resistance of the resulting contact with a battery contact. The magnets I soldered didn't remain strong enough to provide a very firm connection. Unsoldered magnets like these are crazy strong so I would only question the weakened soldered magnet.


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## LuxLuthor (Aug 18, 2009)

tino_ale said:


> Good to know but I am still wondering about the resistance of the resulting contact with a battery contact. The magnets I soldered didn't remain strong enough to provide a very firm connection. Unsoldered magnets like these are crazy strong so I would only question the weakened soldered magnet.



As those using them can affirm. Mine aren't weakened.


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## hank (Apr 11, 2012)

This may help, Cornell describes a way of protecting magnets while they're being soldered: 
http://myip.cctec.cornell.edu/index.cfm/ts.details?tk=K4AB2317153854938841&from=search

"Cornell researchers have developed a method to temporarily increase the demagnetization temperature of permanent magnets during high temperature assembly events such as soldering. The magnet's demagnetization temperature is increased by lowering the demagnetization force inside of the magnet. This is accomplished by placing ferromagnetic/steel components around the magnet during periods of elevated temperatures. The magnetic field generated by the components decrease the demagnetization force within the PM which in turn results in an increase in demagnetization temperature.

The components are removed after soldering and can be reused. By using this method, magnets can be permanently attached to an assembly via soldered without demagnetizing."


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## eh4 (Apr 11, 2012)

good info Hank, thanks.


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## pinetree89 (Apr 12, 2012)

Perhaps an easier method would be to solder something ferrous to the wire like a small washer or some such, then the magnet will be attracted to the washer AND the cell top. No magnet soldering required.


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## arnstein (Apr 14, 2012)

You are a smart guy pinetree.


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## jasonck08 (Apr 15, 2012)

Neodymium magnets will loose most of their magnetism if exposed to temperatures above 85C for any length of time.

Secondly, I once tried soldering to a very powerful magnet and had liquid solder splash onto my arm. After that experience I've come to the conclusion that soldering to magnets is very dangerous business!


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## dimak (Apr 15, 2012)

pinetree89 said:


> Perhaps an easier method would be to solder something ferrous to the wire like a small washer or some such, then the magnet will be attracted to the washer AND the cell top. No magnet soldering required.



:thumbsup: Simply brilliant! Amazingly simple!


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## jasonck08 (Apr 15, 2012)

pinetree89 said:


> Perhaps an easier method would be to solder something ferrous to the wire like a small washer or some such, then the magnet will be attracted to the washer AND the cell top. No magnet soldering required.



I use alligator clips but have thought of using washers too.


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## TakeTheActive (Apr 22, 2012)

*Better to Use Terminals...*



pinetree89 said:


> *Perhaps an easier method would be to solder something ferrous to the wire like a small washer* or some such, then the magnet will be attracted to the washer AND the cell top. No magnet soldering required.


A washer is so '_crude_'. 

I use: *AMP Ring Terminals Size 22-16* (except the box of 1250 that I bought at a Computer Fair a couple of decades ago are insulated and non-insulated was the first GOOGLE LINK which included a picture  ).


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## Quest4fire (Apr 25, 2012)

*Re: Better to Use Terminals...*

If one were to search diligently, LuxLuthor caves in to shameless begging and pleading on the part of fellow CPF'ers in a previous thread and shares his tips and tricks for successful magnet soldering (Thanks again Lux!), no doubt aquired through much experimentation. Follow his methods and it's a breeze!

lovecpf


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## hank (Jun 25, 2012)

*Magnets in cans with leads soldered*

Here they are for sale cheap. Great site for science education material.
http://www.mindsetsonline.co.uk/product_info.php?cPath=1_429&products_id=119

"Magnetic pins useful for making electrical connections - e.g. for joining circuit boards to batteries. Also a useful component for such projects as low-voltage lighting, information display, etc. Supplied individually."

Note "Supplied individually" -- so buy four, or eight -- they're sturdy little metal cups, smaller than a pencil eraser, with wire lead soldered on the closed flat side and one pole of the magnet exposed on the open flat side. Might be the magnet is crimped or glued into the can, or else it's just strongly holding itself in there.

You can shrinkwrap all but the face you want in contact with the battery -- put two "positive pole exposed" contacts on one pair of charger wires. Put the other pair together on a different device. That way the exposed metal surfaces will stick to opposite ends of a battery fine but will repel each other, so you'll have less likelihood of a short circuit if you happen to have a charger that's not protected against that.


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## GregP507 (Sep 19, 2016)

https://www.youtube.com/watch?v=WtUe8E5LQPw


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## Lynx_Arc (Sep 19, 2016)

I've got some magnets on order that have a hole in them with a beveled area (countersink). I plan on trying to find some brass machine screws that fit in the hole and use them at a way to use clip leads with magnets. They make several sizes of these magnets and I will see what size flat head screws are needed for them. If the magnet itself doesn't have a lot of resistance the screw doesn't have to be flush with the face of the magnet so it should be easy to find a screw to work.


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## kjenglish (Sep 19, 2016)

Old thread, but I had some conductive glue that I would imagine would work for this if soldering was unsuccessful.


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## Overclocker (Sep 19, 2016)

i just tried spot-welding a pre-soldered nickel tab onto a small magnet. while electrically sound it's not very strong mechanically (the magnet's coating tends to delaminate)

but i think this has potential. i'll try applying some strong epoxy first, then spot welding, then waiting for the epoxy to cure

take note i'm using a small battery-tab spot welder. very little heat. definitely less than 40 C


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## Overclocker (Sep 20, 2016)

..................................


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## Lynx_Arc (Sep 20, 2016)

Overclocker said:


> i just tried spot-welding a pre-soldered nickel tab onto a small magnet. while electrically sound it's not very strong mechanically (the magnet's coating tends to delaminate)
> 
> but i think this has potential. i'll try applying some strong epoxy first, then spot welding, then waiting for the epoxy to cure
> 
> take note i'm using a small battery-tab spot welder. very little heat. definitely less than 40 C


If you had a strong enough magnet you could wrap the tab around the magnet and weld it to itself and let the magnet hold the tab against the cell.


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## fivemega (Sep 20, 2016)

*If you don't have skill for soldering, use similar magnets to this and small screw/nut to connect wire.*

http://www.ebay.com/itm/Wholesale-S...hash=item2100ece632:m:mESsFrT2eN60servoxCukyw


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## Lynx_Arc (Sep 20, 2016)

fivemega said:


> *If you don't have skill for soldering, use similar magnets to this and small screw/nut to connect wire.*
> 
> http://www.ebay.com/itm/Wholesale-S...hash=item2100ece632:m:mESsFrT2eN60servoxCukyw


Great minds think alike.... they make round ones too (post 30).

http://www.ebay.com/itm/171188340293?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


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## eh4 (Sep 21, 2016)

Lynx_Arc said:


> If you had a strong enough magnet you could wrap the tab around the magnet and weld it to itself and let the magnet hold the tab against the cell.



If the magnet pressed a thin, flat conductor against the battery terminal, you'd be set. No worry about how good or bad of a conductor the magnet was (the magnet's plating was).
I'm seeing a small rare earth magnet epoxied inside of a small copper cup, the cup soldered to a wire.


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## Gauss163 (Sep 27, 2016)

Worth emphasis: magnetic connectors may increase the risk of shorts. Namely, since *the entire can of the cell is negative*, if the wrapper is damaged and the magnet shifts it can cause a short by providing a current path between the red arrowheads below.


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## Poppy (Sep 27, 2016)

Olight has a charger that uses magnetic leads.

http://www.olightstore.com/batterie...l-magnetic-usb-charger?tracking=57e558f188f26

I cut a few alligator clipped jumper wires in two, and soldered magnets to the wire ends. Most of the magnets demagnetized, so I just use an additional magnet.

Those of you who used conductive adhesive I'd be interested in how well it worked for you.


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## Gauss163 (Sep 27, 2016)

Poppy said:


> Olight has a charger that uses magnetic leads.
> 
> http://www.olightstore.com/batterie...l-magnetic-usb-charger?tracking=57e558f188f26 [...]



Glancing at their photos, it appears that Olight's magnets are prone to the same type of shorts should the wrapper get damaged. They appear to have a circular ridge to help anchor the magnet around the button top, but that won't help on many cell designs, and the ridge will actually make it easier to achieve a short (in some cases).


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## novarider (Dec 19, 2016)

Gauss163 said:


> Worth emphasis: magnetic connectors may increase the risk of shorts. Namely, since *the entire can of the cell is negative*, if the wrapper is damaged and the magnet shifts it can cause a short by providing a current path between the red arrowheads below.



So I'm clear if the magnet touches ANY part of the black it will short out? Including the little rim around the silver even if the wrapper is not damaged? Like if the magnet slides just a little to the side will it short out?


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## Gauss163 (Dec 19, 2016)

novarider said:


> So I'm clear if the magnet touches ANY part of the black it will short out? Including the little rim around the silver even if the wrapper is not damaged? Like if the magnet slides just a little to the side will it short out?



No, the black is an insulating ring. What you need to worry about is connecting some point of the metal button top (positive) to some point of the side of the can (negative).


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## Lynx_Arc (Dec 19, 2016)

novarider said:


> So I'm clear if the magnet touches ANY part of the black it will short out? Including the little rim around the silver even if the wrapper is not damaged? Like if the magnet slides just a little to the side will it short out?



If you want to be sure take a voltmeter and put one lead on the top and the other area and if there is a chance of power flowing you will measure voltage.


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