[NJARC] safely weld/solder Lithium battery cells?

Wed Jul 27 11:51:42 EDT 2016

This is an ongoing problem with battery powered tools in general.  They work great when first bought but when you need them later on the battery has passed on.  I believe that Lithium batteries are indeed dangerous and are probably the reason for the mysterious downing of passenger aircraft in the last few years.  We have all seen the YouTube videos of laptop computers catching fire on conference tables.
I have soldered a heavy zip cord to a battery powered drill terminals and used a 12 volt lead-acid gel cell for power.  Perhaps you could do something similar?  Lead-acid batteries do well under constant trickle charge so they should be there for you when you need to use the tool again.  The only down side is the umbilical between the tool and the auxiliary battery.Jim

      From: Pete Grave via NJARC <njarc at mailman.qth.net>
 To: dino66 at optonline.net; oldradio at comcast.net; mattr04 at hotmail.com 
Cc: njarc at mailman.qth.net
 Sent: Wednesday, July 27, 2016 10:00 AM
 Subject: Re: [NJARC] safely weld/solder Lithium battery cells?

Matt; I am with Bob & John you made a mistake don't make two buy a new one. Only suggestion I have and I think its a bad one is rebuild use a dielectric glue. I checked ebay and no rebuilds offered on 28v whats that tell you?. I have a beautiful Snap on battery impact has served me well orig cost $500.00 batteries are done I can buy a new one cheaper than batteries. Good luck with it Pete 

-----Original Message-----
From: Robert Bennett <dino66 at optonline.net>
To: oldradio <oldradio at comcast.net>; 'Matt Reynolds' <mattr04 at hotmail.com>
Cc: 'NJARC' <njarc at mailman.qth.net>
Sent: Wed, Jul 27, 2016 10:40 am
Subject: Re: [NJARC] safely weld/solder Lithium battery cells?

Just remember
Reply = Poster
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_________________________________________________________
Matt -
 I checked some "youtube" vids on this subject. Not liking what
I'm seeing. I agree with John and would take the lick and spend the 100
bucks. What's a hospital trip worth?

Bob Bennett

Hi Matt,

spend the $100 and dispose of the old one.

73, John

I took a gamble at a flea market two weeks ago and bought a contractor grade
Milwaukee 1/2" battery hammer drill. It was in the case with two 28V (yes,
28, not 18) Lithium Ion Batteries and a charger, for 30 bucks. The seller
said the batteries were good, but didn't last long. 

Turns out, they are so dead they've gone dormant and won't charge. I'm going
to bench test the drill with a bench power supply to see if the drill at
least works. If it does, I will work on making it cordless again. 

Unfortunately, I've found that these batteries are about 100 bucks each (!)
and it turns out (per Batteries Plus\Batteries & Bulbs) it's illegal to
commercially rebuild Lithium Ion Battery packs in NJ. 

I've been investigating what my options are, and I'm considering rebuilding
the packs myself, but from what I've read, Lithium cells are very heat
sensitive and it's very dangerous to rebuild them via soldering. Evidently
they are generally spot welded together by the tabs at the factories. 

I have at home what I was told is a "thermocouple wire welder" which I
believe uses an arc (presumably like discharging large caps) to weld metal
together. Is this a "safe" way to weld lithium cells? Can you discharge caps
into lithium cells to weld without harming them? 

I would be fine with converting the cells to Ni-Cd, but I'm sure the
protection circuitry of the pack won't permit that. The charger that came
with the drill can charge 18v Ni-Cd or 28V lithium, but I'm sure the pack
circuitry is different. I might be better served hunting down one of those
18v packs and rebuilding one of those instead. 

I just thought I'd shoot this out on the reflector in case anybody else has
had experience with this. The packs have 7 3.7V "moli cells". 

Regards, 
Matt 

_
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