Picture of Bring Dead Ni-Cad Batteries Back To Life
Are you tired of having your Ni-Cad batteries that refused to charge and simply die?

So what do you do with them when they die?
Just throw them in the trash - which harms the environment?
Or just take them to a recycling facility for them to be recycled?

Well, here is the best solution, bring your dead batteries back to life that can save you a chunk of change - By zapping them!
Here is one great instructable, Revive Nicad Batteries by Zapping with a Welder. Of course, you will need a welder, and not many people has one... So I came up with this idea that almost anyone can build!

UPDATED: This instructable has been featured in hackaday!

This instructable involves hacking a device that operates on 300 volts and can be dangerous if not handled correctly. So, I am NOT responsible whatever happens to you using this information.
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Step 1: So, Why do Ni-Cad batteries die?

Picture of So, Why do Ni-Cad batteries die?
Why do Ni-Cad batteries die?

They don't exactly 'die', it is the sulfur crystals that is causing the problem.
The crystals are formed and begin growing caused by:
  • Overcharging the cell
  • Leaving the cell in the discharge state for a long time
  • Memory effect
  • Being exposed in high temperature

After the crystals has begin growing inside the cell, it eventually touch both ends of the cell terminals. This shorts out the cell and preventing it to be recharged again...

But, the good thing is the sulfur crystals can be easily destroyed, by putting a hefty surge current through the cell... This vaporize the crystals and the battery should be good as new again!
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jennyxls1 month ago
Hi Plasmana. Loved the instructable. Thank you so much.I have bought too many cordless tools because they are cheaper than new power packs. Having hacked the packs apart, they all have the same cells - now also separated. How can I test individual cells (1.2V) a) to ensure they will be rechargeable (or are they always rechargeable); b) how do I discharge them - I'm thinking a circuit with a low volt bulb until it goes out, then check with a multimeter or battery tester. I don't want to do all this zapping and then discover one cell is entirely dead and have to remove it and start over. I'm 64 and every second counts!
I have an assortment of wall chargers (one for each too!!). How do I test that these are working? Some have LEDs, some of which light and others not so much. They have varying DC voltage at the input plug and the same at the tabs inside the base. Why do some have two large tab and others have an extra two tiny ones?
Lastly, can I charge NiMh packs on a NiCd charger of the same voltage?
Your latest favourite and follower, jenni.
KevinD64 months ago

Can anyone confirm whether you can recharge NI MH rechargeables on a Ni Cad recharger


taterz10 months ago

I like the idea of a capacitor to bring back life to NiCad batteries. How well does this work in cordless power tools. I have a Craftsman 19.5v drill and power saw. Using this method, would zapping the battery pack have any worthwhile effect as opposed to, say, a battery charger or welder? I like the capacitor method because of the high voltage hit. It seems it would do more that just getting a battery to accept a charge.

vlre11 months ago

Tried you method yesterday on 8 years old B@D drill battery, NiCad 1.2Ah. Found 6 dead cells. Zapped them individually and the battery altogether. Today the battery works fine, holds charge. Don;t know for how long, but it DOES. B4 it was not even taking any charge. So, thanks a lot. And, guys, be careful, I zapped myself by mistake. Kinda hurts...:-(

JaredN1 year ago
Would it be possible to do this one at a time to the individual cells of a battery connected in series? As in what you would find in a drill battery pack. Mine has 24 cells in it and I don't want to detach the metal tabs on each of the batteries.
zubain1 year ago
There are no sulfur crystals in a nickel cadmium battery. These are needles of cadmium that grow from the negative electrode, puncture the separator, and touch the positive electrode, thus creating a short. What this procedure does is to force a high current through the dendrite (needle of cadmium) and melt it so as to remove the short. Further, just for academic information, there are two kinds of shorts: a soft short and a regular short. A soft short is one where the dendrite does not make very good contact with the positive electrode. It is similar to connecting a high-value resistor accross the cell. A cell with a soft short will be able to get charged, but will get self-discharged when it is kept idle. A regular short is where the dendrite makes a good contact with the positive electrode. A cell with a regular short will not be able to get charged since it will shunt the charging current through the short and will deprive the electrodes of this current for getting charged. You can also check the effectiveness of this procedure by observing the self-discharge of the battery. If the battery is able to hold most of the charge for a reasonable period (a few days or a week) then the procedure is effective and you would have incurred substantial savings! This procedure is not applicable for cells that have failed due to dry-out. Dry-out happens when the cells have been continuously over-charged and have lost the moisture from the electrolyte, making it non-conductive. This can happen due to many reasons such as a bad seal in the cell, bad cells in the battery leading to over-charge, extended over-charge due to long time charging on a manual charger or due to a defective automatic charger.
Sorry for the very long comment. As a battery technologist, I thought that I could provide more insight into how and why this procedure works, its effectiveness and its limitations.
crazypj1 year ago
Really like the idea of using a capacitor plus all the circuitry from disposable camera, much safer than 'taping' wires onto battery
Could also place battery into 'explosion proof' cylinder or somesuch metal box with plenty of expansion room?
polkapolka1 year ago
Is polarity an issue?

If so, how do you find polarity on the capacitor, and how do you allign the polarity of the capacitor with the polarity of the battery to be zapped?

Thanks, PP
I use jumper cables and a car battery. Works everytime.
Melibokus2 years ago
Hello, thats fine. My problems are 3 NiCd 18V accus. From a screwdriver. How shall I refurbish these. Otherwise they are poison rubbish.
luig3 years ago
hey could this be used on bigger batteries eg. NiCd rc batteries 7.2 volts.
timmartha5 years ago
Back in 1992 when i first recived my ham radio ticket My instructor told my class that you can strike a rechargeable battery with a car battery charger 15 times and it would bring most of them back to life. I have sucsesfully done this many times. All have come back to life. I hope this helps.
I took your advice and used a car battery charger - it worked a treat!
Plasmana (author)  timmartha5 years ago
You mean short out the battery 15 times with a car battery?
Yes. Put the pos from the car bat to the rechargeable battery pos, (using jumper cables) then strike the neg 15 times. Do not hold it to the battery just strike it. If you hold it to long it can explode.
Plasmana (author)  timmartha5 years ago
Ahh okay, I have been told that is it very dangerous to even strike an ni-cad battery with an car battey, I guess they are wrong :P
I think he meant car battery charger, not the battery itself. This works I used it to bring back an old dead cordless drill.
What happens over time is the polarity in the batterys revers and this will realign them. After you strick them put them in a charger for the length of time it would take to charge them. Glad that i could help.
Plasmana (author)  timmartha5 years ago
Thanks for your advice, I will try that when i get more dead batteries :-)
do you know if that would work with electric scooter batteries?
As far as i know it will only work on any 1.5 or 1.2 volt batteries. It may work up to 6v small ones but not sure.
ok, thanks
phil galati6 years ago
I have known about this since the 70's when I used to fly radio control plains. It does work. Your process is much nicer and I will try it. Thanks for the great idea Phil Galati
I didn't know you could fly an entire plain remotely.
lol, I thought the same thing!
Plasmana (author)  phil galati6 years ago
Thanks for your nice comment! :-)
chadeau4 years ago
Still looking for an answer to whether or no this works with NiMh batteries...promt response appreciated !!!
There is an answer of sorts by Unit042 above to zack247's question Jan 6
dmcdonell3 years ago
Anybody with success restoring Ni-cad batteries live in the Buffalo, NY area? I would pay to restore a Craftsman power tool battery, let me know,
codongolev3 years ago
if I can track down a disposable camera (I think we have a few from when we cleaned out my grandmother's house), I'm totally doing this to my roomba's battery. it'll save me 25 bucks. (I believe, based on others' stories, that the first battery on the positive side is usually the bad one [they're in series]. however, I'll probably zap all of them just in case.)
alright, folks. here's what just went down. I was thinking about this instructable, and I really wanted to do it. however, the only disposable cameras in the house were ones that my mom was keeping for some reason, and I'm sure it wasn't for me to take them apart. so I thought about it a while, and I remembered playing around with this AC adapter (that's a pretty old instructable, by the way, so keep in mind if you decide to read it that at the time I was still around middle school/high school freshman age). I thought, "that produces high voltage!" so I tried it. my setup was three nine volts in series to create 27 volts, which was then fed backwards (as per the instructable) through the transformer, then over to the battery. by the way, you can't just connect the nine volts then shock the batteries. to create the high voltage pulse, you have to attach the battery to the transformer, then repeatedly connect and disconnect the batteries so you get a spark. otherwise there will be no flow and you'll be wasting your time.

thought I'd share this, as it was very helpful to me (ran my roomba today for about an hour or so, so I'd say it worked especially seeing as before it couldn't even make the startup noise).
Nice 'ible, I've been doing this for years to bring NiCad batteries back to life (and no, it doesn't work on other chemistries, like NiMH). Usually I just turn on my 12V power supply, which charges up the output caps, turn off the power supply, then quickly zap the battery with the stored charge in the output caps. 12V is plenty when backed up by nice big caps (like on the output of most power supplies).

Don't think your batteries are going to be "good as new" afterwards though. Yes, you can get some more life out of the battery, but I've found they never have the same capacity afterwards (apparently it does some irreversible damage) and it only works a few times on a battery before it's gone for good. For this reason, I don't like to do it on a battery from a multi-cell pack -- then you just wind up with a weak battery in series with stronger ones, which is doomed to be overworked by the stronger cells and will die very soon anyhow.
azmatanwar3 years ago
Can we use this trick on 12 V car battery??? regards.
MandingaRes3 years ago
Excelente!! Gracias por compartirlo.
aduy3 years ago
i just made this instructable about soldering onto batteries
and i saw this it looks very interesting. will this work with multi-cell batteries, like those from cordless drills, rc cars, and nicad laptop batteries?
sasrf4 years ago
an idea !! would it be possible for electricals in a domestic fluorescent tube lamp to be modified to supply the high voltage ?? it's just an idea, I am not an engineer, maybe someone can comment !!

Thank you .....
sasrf 04/03/11
craneum sasrf3 years ago
or how about a laptop or pc power supply? Most laptop ps are 12-20 volts and a Pc ps supplies 5v and 12v.
Only thing I'm wondering is amps... seems like thats the key to the whole thing. Perhaps for single 1.2v cells it would be fine but for a larger bank of cells you may need something that supplies 30+ amps when it delivers the voltage? You know they always say its not the volts that kill ya, its the AMPS.
Shaji473 years ago
It is a nice tip..... but an disposable camera is not available in our village. How to make that high voltage circuit? lol, hlep me please....
techno guy3 years ago
So the negative of the cap goes to the negative of the battery and same with positive?
m1sterb0b4 years ago
Now, I've done some researc hof Ni-Cad batteries and some on NiMH batteries and I still have yet to figure something out. a NiCd battery is a dry cell battery. Which means that the only "chemicals" involved here are Nickel and Cadmium. When the cell is fully charged the cathode is composed of Nickelic Hydroxide, it will either get +3 or +4 (lose 3 or 4 electrons) and become either NiOOH (+3) or Ni(OH) (+4) and When one connects a load to the cell the anode is oxidized and the cathode is reduced. Electrons leave the anode where the cadmium is oxidized and forms Cd(OH) , plus 2 free electrons. These two electrons go to the cathode where they reduce the Nickelic Hydroxide to form nickelOUS hydroxide or Ni(OH) (where the nickel has a charge of +2). In all the stuff I've studied show that theres no way for sulfur (S) to exist in a NiCd battery. The only chemicals I've noticed are nickel (Ni), cadmium (Cd), oxygen (O) and hydrogen (H). If I'm missing something if someone could shed some light on it for me, I'd appreciate it. but as far as I know, and have seen, no sulfur exists in a NiCd battery! (to cite a source, one place i copied and pasted info from was:
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