Author Topic: Don't use magnets with li-ion cells! Dead-short danger!  (Read 34130 times)

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Offline Karl

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #30 on: September 29, 2006, 10:28:14 AM »
Well, I don't mean to stir things up here but...but...I do use magnets--the gold plated type--but, use Superglue to attach them so, I not only have the high strength of the magnet attaching itself to the battery but also, Superglue.  I will admit I haven't dropped one of my lights so powered by this setup so, I can't attest to the shock stability but.....
One problem I just resolved with this setup--the extra length didn't help when charging--wouldn't fit. No problem!!  I just take a pair of small pliers and torque 'em off!!   No problem.  Wadaya think??


Karl

Offline ganp

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #31 on: October 23, 2006, 11:55:01 PM »
I've just turned a body especially to take AW's 18500 protected cells (with magnets)...
I'm planning to use a thin delrin washer glued to the top of the cell to prevent the magnet moving sideways.

Oops - watch those vents :icon_scratch:... maybe on the back of the LE.

Colin.
« Last Edit: October 24, 2006, 07:11:33 AM by ganp »

Offline xiorcal

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #32 on: January 31, 2007, 11:39:36 PM »
How would an O-ring go on a magnet?

Offline Geologist

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #33 on: March 04, 2007, 10:39:33 AM »
How would an O-ring go on a magnet?

The washer refered to by ganp would be rigid.  Attached to the battery, it would provide a nice recessed spot in the middle for the magnet.  That way, the magnet would not shift around but stay in the middle of the washer.
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Offline Brightnorm

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #34 on: April 22, 2007, 08:03:53 PM »
...I'm planning to use a thin delrin washer glued to the top of the cell to prevent the magnet moving sideways.
Leef is experimenting with magnets locked within delrin washers. Lighthound may eventually carry them.

Brightnorm

Offline vortechs

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #35 on: April 25, 2007, 06:11:15 AM »
Lighthound is now carrying Leef's "safety magnets".  See http://www.lighthound.com/index.asp?PageAction=VIEWPROD&ProdID=2677

Offline Brightnorm

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #36 on: April 25, 2007, 08:32:24 AM »
Great, thanks.

Brightnorm

Offline LuxLuthor

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #37 on: May 14, 2007, 04:00:09 AM »
Lighthound is now carrying Leef's "safety magnets".  See http://www.lighthound.com/index.asp?PageAction=VIEWPROD&ProdID=2677

I get these free from AW whenever I buy batteries, and must have 50 magnets unused.  Would be easy to find a plastic washer and some epoxy.  I just used Arctic Silver epoxy to attach my one magnet I used in L2.  Works great
« Last Edit: May 14, 2007, 04:02:52 AM by LuxLuthor »

Offline borealis

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #38 on: May 23, 2007, 03:07:21 AM »
Hi.

I would agree that it's never a good idea to use a magnet on the li-ions or really near any power circuit.

I tried the 2 part epoxy. It works, however it does not last long under the potential heat.

Tested the solder blob, which has always worked for me. My only concern is certain FL LED moduals that have a rather smooth + pole (on the led modual, not the battery). No matter how clean or rough you make it some times the solder won't hold for long.

 I came up with a simple solution for my C2. I got battery pole spring (those tapered ones) and a snap in plastic washer drilled the proper size for the sping and with a few needle noze pliers tweeks snaped the washer with spring into the led modual's flat + pole.

It's the safest i've seen as yet.

Good Luck.
« Last Edit: May 23, 2007, 03:08:54 AM by borealis »

Offline Edwood

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #39 on: May 28, 2007, 03:31:50 AM »
Charging cells on the 123 Nano charger for my Orb Raw Ti is going to a pain without spacer magnets.  Otherwise I'd have to permanently mod  my Nano charger, which would make it useless for charging RCR123's.

-Ed

Offline Atomic Chicken

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #40 on: May 28, 2007, 11:15:37 AM »
Greetings!

when charging cells with magnets, impact danger is not there. unless you are slamming charger around :D but don't discount magnet sliding during placement in charger. if plastic wrapper is damaged, could ground to body.

but due to additonal resistance, could cause cell to charge differently then bare. this would be more so when charging in series. don't recommend charging li-ion cells in series.  unless a pack has been specifically engineered to do so.

this charging clamp works for all cells, flat top or not



Charles... great minds MUST think alike, as I use the EXACT same setup when charging my Li-ion cells using my Triton!

Best wishes,
Bawko
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Offline borealis

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #41 on: May 29, 2007, 12:37:40 PM »
Atomic Chicken.

I like your charger / charging mount design  and the  use of copper (oh heavenly copper) speaker wire.


Thanks
« Last Edit: May 29, 2007, 12:43:26 PM by borealis »

Offline CY

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #42 on: May 29, 2007, 04:50:32 PM »
thanks, Bawko..

note in pic how 14guage copper monster speaker wire is soldered for low resistance.
it's also soldered on plug-in end.

brass fittings are lamp hardware, available at most hardware stores. monster wire is available by the foot at rat shak.

clamp easily holds a 12 AA modamag or FM 6x AA adapter.

termination points are critical when charging li-ion cells. there's a +/- .5v
after factoring meter tolerance, if using cheap meter. it's better to terminate at 4.1V setting if you have a choice.

Offline half-watt

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #43 on: August 05, 2007, 11:19:42 AM »
Don't use magnets with li-ion cells! Dead-short danger!

the problem as i understand it:

i've heard of this problem happening if one drops or shakes the flashlight.  the magnet migrates to the edge of the cell, even sometimes moving over the cell's plastic wrapper, and makes contact with the tube/barrel while maintaining contact with the postive terminal of the battery.



my personal solution:

i use a thin fiber (non-conductive) flat washer which i had laying around.   the tiny magnets i use just fit snugly inside of the washer and are approximately twice as thick as the washer.   should i shake or drop the flashlight, or if lateral magnet migration should occur over the course of use, these small diameter washers make contact with the tube/barrel and keep the magnet from shorting out the cell.

been using them for months with no problems (YET!???).  in theory, and in practice (thus far), this has proven to be a workable solution for me.

if anyone chooses to adopt this approach, try to find a non-conductive washer that fits SNUGLY around the magnet.  too tight - ream it out.  just a tad too loose - a wee bit o' Scotch tape to build up the ID (inside diameter) of the washer might be just the ticket.

i've thought of ways to insulate the outer edge of the magnet (e.g., thin strip of electrical tape precisely as wide as the magnet is tall), but felt that this WASHER approach was more of a "half-watt"-proof (aka "idiot-proof") solution.   

please, if anyone feels this to be a bad, or even a mildly deficient solution, kindly Post back and educate me.

Many thanks,
half-watt

Offline arewethereyetdad

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Re: Don't use magnets with li-ion cells! Dead-short danger!
« Reply #44 on: August 05, 2007, 12:24:42 PM »
half-watt, that seems very clever of you.  Sounds to me like it works.   Nice job.  :thumbup: