# Reviving dead NiCd Batteries



## PurpLev (May 30, 2008)

Just came upon this site, and thought others here might find it useful, I have yet to try this technique, but have several dead batteries that might benefit from such treatment (if it works) so I may try it out soon enough

http://www.instructables.com/id/Revive-Nicad-Batteries-by-Zapping-with-a-Welder/


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## lew (Feb 13, 2008)

That's a pretty cool idea. I would probably use a battery charger or capacitor- don't have a Mig welder.

Lew


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## tenontim (Feb 24, 2008)

This looks like a good way to have your name added to the Darwin Award nominees. I have a couple of dead batteries. I think I'll tell my brother in law about this procedure and let him try it. :]


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## PurpLev (May 30, 2008)

*Lew* - I don't have a welder either, I think the idea is to use something with more current than the battery you are trying to revive, so I'll probably juse connect some 9v batteries in series, or something similar to that idea to try and bring my 18V batteries back to life.

*Tim* - post back after you let your brother in law try it out, and let use know how it worked out for you.


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## SteveKorz (Mar 25, 2008)

...Interesting…

I'm certainly letting the brother in law do it…. that's the safest option for me… lol.


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## LoneRider (May 6, 2008)

Personally, I would not risk it, what if the battery was actually shorted between the two terminals? anyway:

From RepairFAQ.com

"Yup-a quick fix it. When cells short due to dendrites, the piece of material that is actually shorting the cell is very thin. So, by forcing a huge impulse of current into the cell, one can vaporize the dendrite-sort of blowing a fuse.

This works, and can revive an otherwise shorted cell. However, it is a stopgap measure at best. First, the fact that one dendrite has formed means that another is not too far behind. Second, the material that was vaporized has now permeated the separator material, forming a resistor that shorts the plates. The cell may no longer be shorted, but will still have a poor charge retention.

Besides, unless done properly, this can be dangerous as large currents are necessary"


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## Chipncut (Aug 18, 2006)

I don't think I would take a chance, because of a possible explosion.

A dead battery could make you dead.


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## PurpLev (May 30, 2008)

True - there is the possibility of electrocution, and electric driven explosion… so these things if attempted should be done carefully and with the utmost level of safety.

I just found this bit of information to be interesting. I do however plan to try this out as soon as I can setup a safe environment to run this in.


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## Chipncut (Aug 18, 2006)

I had a weird thing happen to me once. I had 2, 9V batteries in my pocket, & the buttons on them made

contact, & almost burned me they got so hot.


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## PurpLev (May 30, 2008)

*Dick* -that reminds me, I (stupidly) had some ignite-on-anything-matches in my pockets years back, and someone rubbed against me…. and well… It was very hot… and I didn't have a pocket no more… (note to self - do not carry ignite-on-anything-matches loose in your pocket)

just gotta be careful, like we should be with 100% of our woodworking equipment anyways. nothing new here. just more of the old stuff.


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## coloradoclimber (Apr 7, 2007)

*PurpLev*, I can beat that. When I was young we lived out in the country. As kids and teenagers we all had firearms and hunting and shooting was part of daily life. So one day my brothers and I were out shooting 22 rimfires. When shooting a 22 I usually dump a box of rounds in my back pocket for easy access, dont have to open and mess with a box every time I need to reload. Then at the end of the day I clean out my back pocket and put all the unused rounds back in the box, normally all good.

You know with a 22 rimfire the primer is around the rim, not in the center like in a larger cartridge. So one day after shooting I clean out my back pocket, jump back in the truck and head for home, along the way we stop at the local playground and I start chasing my little brothers around. Now back in the old days we had those TALL metal slides, with no safety sides or any of that. So I chase my brother up the slide and jump on and down I go (you can probably see where this is leading), sure enough, I had left a round in my back pocket. The metal rim of the cartridge got pressed by my butt down against the slide and with the friction of sliding with the rim rubbing against the slide, bang, the round went off. Fortunately nothing was really hurt but my pride, a little bit of a scorch and a rude surprise.


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## PurpLev (May 30, 2008)

*coloradoclimber* - don't even get me started… or I'll have to go into details about how boiling sulfar chemistry experiment goes bad and explodes into melting substance…. still have the scars to remind me of that…lol (yeah, it's a funny memory now, but back then I don't recall thinking of it in a very amusing manner).


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## ChicoWoodnut (Dec 15, 2007)

This sounds like a perfect candidate for "Mythbusters". Maybe they could make a whole segment on it and take it to extreme. We could send them all of our dead batteries for experiments.


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## coloradoclimber (Apr 7, 2007)

Boiling sulfur chemistry with scars !!! YOU WIN 

I did have a can of starter fluid blow up on me, knock me flat and send me to the emergency room, but no scars, I'm still as pretty as ever


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## NY_Rocking_Chairs (Jul 20, 2008)

When I was a kid my father was welding on his dirt bike, he had the bike lying on a cloth ground cover, you guessed it, soon the ground cloth was on fire, with the gas tank still on the bike. Luckily I was able to get his attention and he got the fire extinguisher and put it out before any kind of bad thing happened.

From then on we removed the gas tank before welding and also remounted the fire extinguisher so I could reach it…


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## Steelmum (Jul 21, 2007)

I posted this on the "Mythbusters" site. I want to see what they think. I'll let you know.


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## PurpLev (May 30, 2008)

that is great *Steelmum* - I wasn't aware of that place until *ChicoWoodnut* mentioned it earlier. Can't wait to see what they come up with and say about it… keep us posted if you get any replies please.


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## Grumpy (Nov 9, 2007)

Looks like a dangerous practice to me. I will pass it by son who is an electrical engineer.


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## brianinpa (Mar 16, 2008)

I'll wait until I see it on tv before I try it. I saw the affects a battery can have on an aircraft after the battery had a thermal meltdown. Not much was useable for both the battery or the aircraft.


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## Steelmum (Jul 21, 2007)

This is what I have gotten so far at the Mythbusters site. It seems to be a slow to answer group. It is a forum group, supposedly the Producers check out the stories offered.

I have only gotten 2 replies, one tells me how to recharge button cell batteries. This guy seems to make more sense, he wrote:

Sometime when ni-cad batteries are discharged all the way, the individual cells can become shorted. When this happens, that particular cell will no longer charge and the overall voltage of the battery pack is reduced by 1.25 volts per shorted cell. It is common knowledge that forcing a very high current through the shorted cell can "blast" clear the short and the cell can be made useful again.

The technique that I always used was to first identify the shorted cell with a voltmeter. Next, charge a very large capacitor (30,000uF or larger) to about 15 volts and then discharge the capacitor through the shorted cell. This technique usually clears the short and is relatively safe to do.

What they are doing in this video is forcing a very large current from an arc welder through the entire battery pack to clear one or more shorted cells. Although this should work, it is much more dangerous than using a capacitor that has a limited stored energy and could cause the battery pack to explode.

One word of warning! This only works with Ni-Cad batteries. Do NOT try either method on a lithium battery as it could cause a large explosion and fire.

Now you guys can do whatever you want. If I get a very dead tool it sounds like an excuse to buy a NEW and More Better one. I ain't doing this.


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## PurpLev (May 30, 2008)

Thanx *Mum*

it does all make sense… and I think they were also talking about zapping individual cells in that video if my memory serves me right (or in one of the latest images/pages)


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## Greedo (Apr 18, 2010)

reviving this thread to let know i tried this today on my brother in law's dead 12v NiCad batteries for his 2 Bosch drills.
before that, one battery still took a little charge, but could only screw a few screws before stopping. the two other batteries took no charge at all and didn't make the drills react at all.
i zapped them about ten times with an arc welder, wich partly loaded the batteries and they all functioned again.
charged them and the two batteries that were dead charged for over 30 minutes where the charger used to stop within 20 seconds before, only the one battery that still functioned didn't charge alot longer than usual.

it seems the batteries have gone from zero to maybe 50% of their initial capacity, and my brother in law can use his drills again!


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## boboswin (May 23, 2007)

I'm going to try it with a car battery.


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