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

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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.
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DanC910 days ago
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.
russ_hensel1 month ago

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.

aebe1 year ago

Too easy ! Thank You ! .

Goodwin71 year ago
Awesome project! Also, try using a battery desulfator :D
This also works with a 1 fard capacitor. Also can use 1 fard capaciator for welding the battery tabs.
nofunclub3 years ago
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.....

GaryRPacker3 years ago
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.
gsnoorky3 years ago
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!
merks3 years ago
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.
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
lundbergaj3 years ago
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.
chrisShrews5 years ago
can this be done with kids power wheels 12v batteries. if so thank u , if not is there a way
this trick only works on nicads. Trying it on other types probably won't work
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.
(removed by author or community request)
Kind of hard to argue with success though isn't it?
this trick is used to get rid of the crystal dendrite not to recharge the battery
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!!
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
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
fwierzbicki3 years ago
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
bigdman14 years ago
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!
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?
Ignore th 2 center ones. The ones labeled positive and negative are the only ones that matter.
I guess my battery was too old. It was worth giving it a try. Thanks
Magnusscott6 years ago
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!!
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 -
idobie3 years ago
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.
Peter Lynn, the kite guy???
Darwinfish3 years ago
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."
stevehin3 years ago
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.
I am replying to myself. The battery was a lithium. Is there any way to zap them?
AdeV stevehin3 years ago
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 AdeV3 years ago
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.
AdeV3 years ago
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!
Fun video!! very good thanks,
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.
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.
I've got the same. I'm going to try this next week if I can find my battery pack.
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