Introduction: Revive Nicad Batteries by Zapping With a Welder

Picture of Revive Nicad Batteries by Zapping With a Welder
Nicad batteries often die in such a way that they won't take a charge and have zero voltage. This usually means they're shorted out by crystal dendrite growth.

Here's a method of bringing them back to life by zapping those shorted crystal dendrites away with too much current and/or voltage. We'll use a welder as a power source. You could also use a car battery, a DC powersupply, or almost anything with some voltage. Charged-up capacitors are popular for this because you can get a very fast pulse out of them and still limit the power. it's a lot safer that way. Speaking of which,

If you get killed by a poisonous explosion it means you did something wrong.
Electrocution is a real possibility also.
Ask your parents how to not electrocute yourself with a welder.

If your tool has a non-battery problem, here's how to fix that.

Watch the video and see how zapping is done.
Excellent stills and video shot by Fungusamungus
Excellent Video editing by Noahw

Step 1: Gather Your Materials

Picture of Gather Your Materials

You'll need:

Dead Nicad batteries
Nicad battery charger
Voltage source - we'll use a welder
insulated gloves
safety goggles

Step 2: Check Your Battery

Picture of Check Your Battery

Charge your battery up for a few hours or overnight to make sure it's charged.
If you suspect your charger isn't working you can trickle-charge it from a different voltage source.
To make sure you don't overcharge it put some little lightbulbs from christmas lights in series so the current is below 1 amp. I use 1/2 amp usually.

When you're sure your battery has had a fair chance to charge, check the voltage with your multimeter. Since you're reading this, the voltage is probably a lot lower than the label says it should be.

To see how much current your battery can put out, run the drill. Grab the chuck and stall it to get a feel for how much power it has.
That way you can compare the "before" to the "after" and see which is better.
Science depends on rigorous methods like these.

Step 3: Check Your Welder

Picture of Check Your Welder

Use your multimeter to make sure your welder is supplying DC and whether the gun or the clamp is positive and negative. Welders are sometimes AC and sometimes the polarity is backwards.

Turn the knobs to see what voltage range the welder puts out when no current is flowing.
This one puts out about thirty volts at the max setting.

Step 4: Zap the Hell Out of the Frickin' Battery!!

Picture of Zap the Hell Out of the Frickin' Battery!!

The title says it all.
Tap the positive end of your welder to the "plus" terminal of your battery
while holding the negative end to the battery's "minus" terminal.

You should see some sparks and nothing should get welded to anything.
No welding please. If you get killed by a poisonous explosion it means you did something wrong.
It should feel like something good is happening.

Step 5: Try Out the Battery and See If It Worked

Picture of Try Out the Battery and See If It Worked

Try out your battery. It ought to be much better almost immediately.

Step 6: Zapping Individual Cells

Picture of Zapping Individual Cells

Pete Lynn dropped this battery pack in salt water. It shorted out the cells and it has been fully dead for a year or so. We peeled it apart to get at the individual cells. We scraped the salty cardboard off them and zapped them with a car battery. After that it worked fine.
It's easier to zap an individual cell than the whole pack at once.
Sometimes you can't revive a cell. You can cut or unsolder it from the others and replace it with a good one.


KevinB276 (author)2017-09-04

I was skeptical about this when I first saw it, but shortly afterward my wife reported that our Bissell Perfect Sweeper wasn't taking a charge anymore after using it several years. So I figured out how to open it up and took out the 7.2V NiCd battery pack.

I have an old laptop power brick that puts out 19.5V at 6.5A, which sounded like a good zapper. So I jumpered it to the battery pack for a couple of minutes of Zap time, then tried charging it on the regular charger. Sure enough it took a charge and now runs fine. We'll keep an eye on it to see long it stays good.

Thanks for the inspiration!

ac-dc (author)2016-03-17

This only gets the battery pack working for a while then the dendrites grow more and short it out again. By then the real capacity of the cell is pretty low. Your charger may say it 's done but that only means the charger has stopped, NOT that the cell now has the full charge capacity that it used to.

If you are in an emergency and need the tool to work badly then it's worth a shot but if not, you gained very little making the effort to zap the battery and would be as well off putting the effort into finding a good price on a replacement pack or an entire new tool if you're in the mood for an upgrade.

fran.markham.9 (author)2015-04-02

I just tried zapping two Rigid 18volt batteries that had no voltage and would not charge. One stopped working last summer and the other one died over the winter. They are both working now and have fully charged. Thanks for the tip.....

ac-dc (author)fran.markham.92016-03-17

I think you mean they have stopped charging, not that they are fully charged. They won't be remotely close to their rated capacity once they have degraded to this point.

DanC9 (author)2015-03-20

Works without welder. In a USA standard 110v AC outlet (white wire = neutral and black wire = hot), you can touch neutral wire to negative DC terminal and hot wire to positive DC terminal. Give a quick pop and the battery is like new.

SethS1 (author)DanC92015-10-14

Though technically this is a valid method for this purpose, since you only need a quick tap on the battery leads, keep in mind that all you're doing to get DC from the AC outlet is using ground and hot instead of negative and hot, so from the 60Hz +/- cycle you're basically getting 60Hz +/0 instead of true DC.

ac-dc (author)SethS12016-03-17

What? No. Ground potential is supposed to be as near neutral as possible so you're still getting AC not DC using earth and hot. It's just a bad idea all around and potentially dangerous too, which makes no sense at all when there are so so many other safer options.

Kids, DON'T DO THIS !!

Pilot_diver (author)2015-08-31

would this work for lithium ion 18 volt Ridgid battery. I have both nicad and lithium 18 volt batteries for my rigid tools and I got the regular battery working and am trying to get the lithium ion working. I've been reading a little about possibly changing the 18 650 batteries. any suggestions or help would be greatly appreciated.

ttblaker (author)Pilot_diver2015-10-26

yeah don't zap Lithium ions ever - you can check out you tube videos of guys exploding Li-ion cells by pumping household AC into them from a distance to convince yourself!

bowen93's suggestion is good. usually these batteries fail because the first cell of five (or double/parallel-wired twin cell) gets discharged to zero or even negative voltage. This happens usually after very long periods of storage and is due to that first cell(s) being used to power the battery protection circuit gets run down way below its minimum failure voltage of about 2.7 volts.

While it is convenient to design this way (with 3.7 volts nominal at that first cell being perfect to power a standard 3.3 volt micro controller-like circuit), this is a major design flaw found in most of the first generation packs and only a few manufacturers have moved away from this design I believe.

So open up your pack and see if only a few cells are killed and replace those. I usually cannibalize other afflicted packs for their good cells but you can use salvaged laptop 18650 cells in a pinch. They aren't rated for the same high current but will work fine for less heavy duty tools like drills especially if you don't run them too hard or long, without taking breaks to let them recover from the strain.

Make sure to test all the cells as sometimes random cells will die too, for reasons I can't explain. Remember that for a 10 cell battery, which is really 5 twin/parallel cells wired in series, the cells die in pairs typically.

good luck , and be safe working on those -- esp be very careful, whatever you do , to not short out the raw cells w solder wire or metal work surface or tools etc - as they produce massive instant current and bad burns and/or battery core meltdown can result!

bowen93 (author)Pilot_diver2015-10-13

i agree with Pa1963 dont try it with lithium ion, you can however change the individual cells with li-ion or even get that cell working again, i have managed to get a few cells working again by plugging them into my small li-ion charger i bought from ebay, as it supports protected and unprotected cells, only use this due to my turnigy didnt allow me to put a small boost into the protection to start it back up so the battery would charge again, but if you do that to prevent it from happening again try fitting a small balance charging circuit to the battery case

Pa1963 (author)Pilot_diver2015-09-01

DEFINITELY NOT for lithium ions. They will most likely explode.

SethS1 (author)2015-10-14

I just used a similar method to this on a small scale to revive a couple dead NiMH AA Batteries. I don't have a welder but I used a 24V DC wall adapter used to recharge the NiCd cells in a handheld vacuum in my college dorm, and it only took a couple zaps to get the 1.2V cells to take a charge again. I was also able to use that adapter to get some 7.2V packs working, but for that I basically just kept them wired together in parallel with my multimeter until it read 8V, at which point my battery charger stopped refusing to finish up filling them.

kokdimia7 (author)2015-04-20

Hi, just wanted to thank you Tim and all others so much - I took a 12v car battery charger and put it on the 12V cordless battery and zapped it up to 75 Amps cycled it a couple of time. Then I selected 12V at 2 amps and let it sit for a bit and now the battery runs better than the one that didn't have any problems and maintains a full charge. thanks so much again!

russ_hensel (author)2015-02-05

Just a note to let you know I have added this to the collection: Cordless-Drill-Battery-Maintenance !


Take a look at a bunch of different/similar approaches to this project.

aebe (author)2014-01-25

Too easy ! Thank You ! .

Goodwin7 (author)2013-12-13

Awesome project! Also, try using a battery desulfator :D

dsandds2003 (author)2013-04-12

This also works with a 1 fard capacitor. Also can use 1 fard capaciator for welding the battery tabs.

nofunclub (author)2012-03-01

my father inlaw has 2 electric bicycles , both with dead nicad batterypacs

I will try this trick to save him 600 euros for new batterypacs.....


GaryRPacker (author)2012-02-07

Folks, the only thing I can add is that some batteries have small circuits internally (e.g. Laptop/Ham Radio/ VHF-UHF) and if you exceed that circuits voltage or current you may Zap the whole battery pack into orbit. Just be careful. As an example, My DELL laptop battery has a series of LED's that indicate the amount of rmaining charge so I'm very certain it has a built in circuit, in this case, disassem bly and individual cell restoration would be recommended.

gsnoorky (author)2012-01-04

This site has saved me money, already!: My Milwaukee "Power-Plus" 18V drill came with two batteries and a charger. One batt may prove too far gone--it did go from 0V to about 3.2V, however.--the other batt is "saved" and turns the dirll chuck solidly--as in "days of yore!"

Big; boxy HW stores want $70+ or $80+ for these "Power-Plus batteries.

I'm also working on a Sears Companion 12V battery....

Thanks for all the intelligent inputs!

merks (author)2011-12-13

I have Bosch cordless drill equipped with 12V NiCd battery packs. One pack is OK, but another one don't have any power. When I put that pack on charging, charger signals very soon that battery is full, but when I put on drill, power is zero.
I wonder can I do this zapping with 24V DC from truck battery (two 12V serial connected battery) whch is each about 150Ah.

Many thanks.

solaralternatives (author)2011-12-04

As a 'semi-retired' (read UNEMPLOYED) electronic tech, I cannot stress enough. DO NOT DO THIS! Shocking' a battery in this manner will most likely make it explode! Try using a lower voltage/current, say a 12v solar panel. KipKay uses 2 batteries of similar volatage wired in series for the 'shock' voltage for 12-18v nimh or nicd powerpacks. Youtube has some vids showing how to easily accomplish this

lundbergaj (author)2011-11-28

I'd add one or two refinements to your methods.

If you have a batter pack that is easily openable (the Ryobi 1+ packs open nicely with 6 screws), you can do an even better job of revivng them by shocking individual (or pairs) of calls rather than the whole battery pack. This works well if you have a pack that charged has say 16.8 or so volts rather than 18, it means just 1 of the cells is at 0. You can revive the cell without jolting the rest of the pack.

Also, for a current source, I used my car battery charger (on the 6 volt setting). Since using double the normal voltage works well for shocking the cells, I used the 6 volt setting and did 2 cells at the time. Typically the 2 cells which had read 0 volts would then read about 2.8 volts (but this shock charge would be falling quite quickly). Once I got through shocking the whole batter pack and reassembling it, the 18v pack was reading around 7 or so volts, but the standard charger would still recognize it as a good pack, and be able to charge it up to the full 18v.

My car battery charger is a 10 amp charger, with 6 and 12 volt settings. If you had just a 12 volt setting, I'd suggest shocking series of 4 cells or more. I also liked the fact that my charger, when it draws too much power, switches off to cool down. I typically found the shocking 2 cells at 6 volts til it switched off (usually after about 2 seconds) was enough to re-energize the cells. If they didn't test at 2.8 volts (i.e. sometimes 1 cell wasn't recovered and I'd get a 1.3-1.4v reading) I'd shock them again, or just try shokcing the 0 volt cell again.

I might be wrong about how much voltage is needed to shock a nicad cell back to life. 3v per cell might be more than is good, but I got good results with that.

So, to repeat:

1) If you can easily open the battery pack, do so, and recover cells rather than shock the whole pack.


2) A car battery charger works really well for shocking the cells.

chrisShrews (author)2009-08-23

can this be done with kids power wheels 12v batteries. if so thank u , if not is there a way

adam 101 (author)chrisShrews2011-11-10

this trick only works on nicads. Trying it on other types probably won't work

KellySD (author)chrisShrews2009-09-20

Hey There, I believe this can be done with any battery that has lost power after a charge. They seem dead.... They are not. Try using a short peice of wire to touch the positive terminal to the negative terminal causing a spark. 2 sparks may do the trick. If not it sounds like you need to get a power source that is double your battery voltage and "ZAP" the battery back to life! Positive to positive and negative to negative. Brief touches of both contacts at the same time shock crystals that build up in the batteries internal lead and acid. SO you will wear "smart clothes and eye protection". Good Luck.

kz1 (author)2011-11-06

Kind of hard to argue with success though isn't it?

tverstraete1 (author)2011-10-20

Glad I found this!! I used my battery charger/booster set on the 50amp boost setting. Ran it over the terminals for the 18v ryobi's that have not charged in nearly two years and I now have them charging to nearly full capacity!!!

I also have some newer One+ 18v batteries that were starting to go bad (not hold a charge) and I did one of those (just being cautious) and it is working so much better now.

Thank you!!

Southernman189 (author)2011-09-25

OK I did it! I used a car battery. Just lifted the hood, put POS to POS on dewalt battery and car battery with alligator clips and coated wire. TOUCHED the NEG to the NEG of both batteries (expected to see a spark of some kind..didn't happen) then put the Dewalt batteries on the charger for an Hour..IT WORKSSSSSSS! Thank you for this site. I am passing the word of it to all my friends and even a few
Thank you all again for the tips! Don

MechanicallyDeclined (author)2011-03-16

IT WORKS!!!! I have an 18 volt Dewalt Drill. Both batteries were dead! I saved them for future trade in as a core exchange, for rebuilt ones. I bought cheap ($85) China replacements. Checked polarity with a volt meter on good one, marked positive side with a pencil, alligator clipped the terminal, and used a car battery charger on "Boost"! Positive to positive, negative to negative. THANKS FOR THIS GREAT INSTRUCTABLE! I could've saved$$$, if I had tried this before buying the replacements!

Thanks friend you might have saved me alot of money with the instructions you just gave. I'll try that Battery charger thing tomorrow. I first must find out if the front prong is Positive or negative on the 18 volt DeWalt battery.. we'll see how it works. Don

fwierzbicki (author)2011-08-18

great process but to be a little more accurate when using a mig welder just lift the wire feed clamp so your using static wire in the torch,good post tho dudes--b safe

bigdman1 (author)2011-01-21

I had some Ridgid 18V batteries that sat in my garage for over a year because I got out of the building trade and didn't use them anymore. When I went to charge them for use again, they would not take a charge period. The charger flashed the lights indicating battery packs were faulty. I gave up on them, and due to the price of new ones, I was ready to sell off my whole set of Ridgid tools. I ran across some info on someone doing what this site suggested, came here and got the skinny on the method. I tried it using my car battery charger on the jump start mode which put out 14 Volts. I figured that was probably a bit low, but did it anyways. It worked beautifully, I know have 2 batteries that have been charged and re-charged 2 times. This method works people!
Thanks to the author of this info!

derek_eide (author)bigdman12011-07-23

I have the same batteries but I can't figure out which contacts on the battery are what. The far left contact on the battery is labeled positive and the far right contact is labeled negative but there are two center contacts that aren't labeled. Do you know which is which?

bigdman1 (author)derek_eide2011-07-23

Ignore th 2 center ones. The ones labeled positive and negative are the only ones that matter.

derek_eide (author)bigdman12011-08-04

I guess my battery was too old. It was worth giving it a try. Thanks

Magnusscott (author)2008-12-18

Can you do this with say Lithium Ion Laptop batteries? And if so can you do an instructable on this? I think it would be a big hit!!! Thanks for this idea!!

nalderson (author)Magnusscott2011-07-04

Nope. You cannot do this reconditioning with LiIon batteries of any sort, sorry. (hearsay)
"These degenerative effects are non-correctible on the lithium-based system and only partially reversible on the lead acid." Source -

idobie (author)2011-06-26

Hoping you can help me.
Craftsman,19.2 volt batteries,3 months old, stopped taking a charge. 2 at the same time and charger was not getting warm.

Before buying a new charger, I tried my batteries on a friends' Craftsman portable charger that plugs into your cars' cigarette lighter and they charged perfectly.

Bought a new charger at Sears but no luck. No lights at all, no charge. Back to Sears and clerk tried a new battery in my charger, worked perfectly. Clerk says my batteries are bad but they continue to charge on the car charger every time.

Any advice would be much appreciated.
Thank you.

P.S Have absolutely no skills at electrical repairs.

Greasetattoo (author)2011-05-22

Peter Lynn, the kite guy???

Darwinfish (author)2011-05-21

Thanks for sharing. :D I'll have to remember this.

Also, I love this bit: "If you get killed by a poisonous explosion it means you did something wrong."

stevehin (author)2011-04-09

I ahve a motorola i560 cell phone, it has 4 contacts, 2ground and 2 positive I am guessing, I tried zapping it with a car battery, it is now dead, it was marked with a 4, so I thought that meant 4 volt battery, maybe it wasn't even nicad.

stevehin (author)stevehin2011-04-09

I am replying to myself. The battery was a lithium. Is there any way to zap them?

AdeV (author)stevehin2011-05-12

Nope' fraid not :( And by trying, you've almost certainly zapped the charger circuit which means it's so much landfill now.

Lithium batteries don't "go off" the way nicads do; what happens is the cells get out of sync with each other (so one's nearly flat, while another is nearly fully charged); the circuitry detects the nearly dead one & stops the battery from outputting; but when you stick it on the charger it sees the nearly full one get fully charged & stops the charging process; result - battery that acts like a dud nicad. The only way to fix it is to disassemble, individually recharge each cell to capacity (don't overcharge, it wrecks them), re-assemble, dispose of the spare screw(s), and (in theory) as good as new. In practice, it's easier to bin it & buy a replacement.

stevehin (author)AdeV2011-05-12

thanks for the input. I have taken 3 nicads apart and sapped each cell. Two of the batteries are good again, the third is history. So evidently, some are beyond repair.

AdeV (author)2011-05-12

Cool - I just resurrected a "dead" Bosch 9.6v drill battery :) Must admit, I used a car battery (12v) because I couldn't find my multimeter to test out the welding set.

After a couple of hours on the charger, the drill is now returning more torque than it has for years. Nice one!

EARTHFORSOLAR (author)2011-03-07

Fun video!! very good thanks,

mnagrovemama (author)2010-09-01

I've got a couple of Black & Decker VersaPak batteries (long, tubular, contact only on one end). They are nickel cadmium and say "VP100 Type 2, 3.6 V DC" on them. How can I "zap" these? They are really hard to find anymore so I would really like to be able to "revive" these.

dsandds2003 (author)mnagrovemama2011-02-13

You can also ZAP these with a car battery charger as well. Or i have found them on e-bay as well as Fleet Farm.
I have ZAPED a couple of the bad batteries like this... However i did it a little different. I reversed the the polarity and just touched the terminals 4 to 5 times then placed them in the charger and they haved worked LIKE NEW for about 6 mo. now.

usafa92 (author)mnagrovemama2010-09-03

I've got the same. I'm going to try this next week if I can find my battery pack.

About This Instructable




Bio: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output ... More »
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