Introduction: Bring Dead Ni-Cad Batteries Back to Life

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.

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!

Step 2: What You Will Need for Battery Zapping...

Picture of What You Will Need for Battery Zapping...
I recommend using capacitors as they give a powerful pulse discharge.
Other power source like car batteries and welders are not a good option. Because as they give out a continuous discharge, the wire can be accidentally get welded to the battery terminal and cause them to over heat and possibly explode... You can use car batteries or welder, just be careful what you are doing.

The capacitor type you should use is somewhere about 100,000uF 60v. Unfortunately, that capacitor with an extreme ratings are just way too expensive...

So in this case to avoid paying a chunk of change for a big capacitor, I use disposable flash camera's capacitor instead for this project. Why? Because they are suitable for pulse discharging, and best of all, they are FREE! But they are more dangerous...

So, what you will need for this project are...
  • A disposable flash camera
  • Dead Ni-Cad batteries
  • Wires
  • Battery holder for the dead Ni-Cads (You can use size AAA, AA, C, or D, depending what battery you want to zap. I am going to use an AA battery holder for this instructable.)
  • Small switch (I used a slide switch)
  • High power switch (I used a push-button switch)

You can get free disposable flash cameras from photo developing places like Wal-Mart and such.

And for the tools, you will need:

  • Soldering iron (You might be able to get away with out doing any soldering by twisting wires in place.)
  • Wire cutters
  • Wire strippers
  • Flat head screwdriver
  • Pliers

Right, hopefully, you got everything, so lets get to work!

Step 3: Slaughter the Camera!

Picture of Slaughter the Camera!

Give a general description of the StepNow this is going to be a fairly dangerous part, open up the camera and get the circuit out safely without getting shocked by the capacitor...

(The capacitor in the camera is a large black cylinder thing, it is used for making flashes for the camera.)

First, pry open the camera's case apart with a flat-head screwdriver or just use your hands if you like, but you are more likely to get shocked by the capacitor.
After you taken the camera's case off, discharge the capacitor with a insulated screw driver, and you may get a big loud spark, and after that, the capacitor is discharged... (Use a screwdriver you hate so much, because a fully charged capacitor will leave a scar on the metal part of the screwdriver!)

Great! You had done the dangerous step on this instructable! (Some people say this is the fun part of the instructable because you get a loud spark from the capacitor.)

Step 4: Remove and Add Switch

Picture of Remove and Add Switch

After the camera's circuit is removed from the frame, we need to remove the surface-mounded charge switch and add an external switch. Doing so, you will have easier control of the circuit and less likely to get

Remove the top bit of the charge switch. It will have some tape on the top, so it shouldn't be too hard to remove.

Then solder two pieces of wire on both exposed metal tabs. And solder a 'new' charge switch onto the other ends of the wires.

Step 5: Add the Battery Holder an the Switch

Picture of Add the Battery Holder an the Switch

Then we need to solder the battery holder and the high power switch together with the black capacitor.

Solder the black wire of the battery holder to the lead of the capacitor that is the closest to the grey stripe.

Solder a piece of wire to the other lead of the capacitor.

Then solder the push-button switch to the red wire of the battery holder and the other wire.

Also, the battery holder you just added, that is where you put the dead Ni-Cad battery to zap them.

Step 6: Insulate the High Voltage

Picture of Insulate the High Voltage

Okay, you are almost done! All you need to do is somehow insulate all the high voltage parts...

You could put it in a nice project box... But I don't have a project box available, so I just put tape on all of the bare metal parts and taped the bottom of the camera's circuit.

And you are done!

Step 7: Zap the Hell Out of the Battery!

Picture of Zap the Hell Out of the Battery!

To zap a dead Ni-Cad battery back to life, put the Ni-Cad battery into the 'zapping' battery holder and a good alkaline battery into the battery holder on the camera's circuit.

The turn on the charge switch and wait for the neon/LED to glow. When it starts glowing, push the push-button switch and you may hear a loud 'POP'. That is OK for it to pop, it shows the battery has been zap an it is alive! But to be sure the sulfur crystals are really vaporized, zap the Ni-Cad battery one more time...

After zapping the Ni-Cad battery, charge it in its charger to really get it working again.

This works for me very well, I hope it works for you!

If you have any questions, or need help, or found an error, or anything, make a comment!
I like comments! :-)

Also, could you spare your few seconds on voting this instructable? Please?


Capt Caveman (author)2018-01-17

As this has been up for such a long time, I was wondering if there was any updated info for this as I really dont wanna kill a ni-cad if I really don't have to. I'm also wondering if this would work with a battery pack, you know the type that comes with cordless drivers, drills and such like?

zubain (author)2013-09-17

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.

fip (author)zubain2016-01-21

Hi Zubain, Do you think we can do this instructable with laptop batteries? Also (probably more difficult) Do you think we could do this with internal batteries, like iPhone batteries?

FoxxieFox (author)fip2017-02-12

absolutely not!! They do not take any sort of over charging at all and will not tolerate being charged if they're run completely flat. they will explode violently if overcharged too much.

and if they dont overheat and explode they will have 10-fold less life. so instead of 10 years maybe you'd get a half a year to a year out of them at best.

if you want to try to revive LI ION or LIPO batteries. use slow charge rate and constant current 25mA maximum over a long period of time. and set voltage limit to 4.0v and no higher of voltage.

PaulaW37 (author)2016-06-12

Use my police stun gun. and zap the hell outta these dead rc ez starter battery packs.there 15 year old cells and still charge 1999 year purchased nicd.

FoxxieFox (author)PaulaW372017-02-12

Use a diode rated for ultra high voltage to make sure the battery gets the right polarity. and so the battery doesnt feed back into the stun gun.

crazyg made it! (author)2016-12-30

lots of fun . seems to work quite well . good when charger says its full. zap it and it charges up some more.

Less Opinion (author)2016-12-27

I have a bad habit of letting battery's set around unattended and very often when I place individual batteries into a charging unit it will reject them due to the fact that they are super dead.

Here is the hint! I have a glass top electric stove in my kitchen.

1. Turn a burner on high heat for about a minute.

2. Reduce heat to medium.

3. Roll the battery back and forth across the burner, Do Not let the battery set in one position over the burner, keep rolling the battery back and forth over the burner until it is very warm to the touch,

Not Burn Your Self Hot! Just very warm. This will excite the electrons in the battery enough that the charger will recognize positive from negative and most of the time they will charge and operate normally.

4. The best practice is to Always keep them charged however if your like me, we forget.


KevinD6 (author)2014-11-17

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


Lee Wilkerson (author)KevinD62015-10-12

My NiCd charger says it will also recharge NiMH batteries.

Yes, this is the safest method. If the charger's manufacturer says so you can charge both with any type of charger. Typically though each one is for its own kind of batteries. However, I have rebuild a few old NiCd power packs using NiMh batteries, charged them with a smart NiCd charger made by B&D and so far did NOT have any adverse effects whatsoever. Performance wise the NiMh outperform NiCd in the capacity category and last considerably longer. NiCd on the other hand seem to be able to provide a bit more initial torque than NiMh but I have not been able to reliably substantiate this claim. All in all, I believe from personal experience that NiMh are a much better replacement for NiCd overall.

True sir, most smart chargers can charge either type. Also, I have observed from my own experience that NiMh batteries start with a higher fully charged output voltage (I know that NiCd batteries only charge up to 1.25 volts per cell) and last far longer than their NiCd equivalents.

grelfod (author)KevinD62015-08-10

NO you can NOT

Totally different system

ΧωρίςΌ (author)grelfod2015-10-18

They are a different system but they are not "totally" different. If one has a "smart" charger, especially if it was manufactured after 2005, charging either type of batteries with a NiCd charger should be no problem. In general however, I wouldn't recommend charging NiCd batteries with a NiMh charger.

MrLWJ (author)2009-11-01

could this  be used to give laptop batts a second life?
those suckers are pricey.

beehard44 (author)MrLWJ2010-02-27

i woudnt risk it!
li-ion or li-po batteries are very dangerous! but you can rebuild them!
just open it up then order the same type of "cells" that look like batteies, then just replace!
it is somewhere on the net....

fip (author)beehard442016-01-21

Thank you for answering this question!

maxpower49 (author)beehard442010-04-13

what if the laptop battries are AA sized and you know they are Ni-Cad

matstermind (author)MrLWJ2010-04-04

late reply, but you could try freezing the batteries for 12-14 hours then cool down recharge then discharge several times. it worked for me with one battery, but not with the second, look around the internet for more information

fip (author)2016-01-21

Wow!! Thank you so much!! By the way, I have two questions for everyone. 1. Can this be altered for a laptop battery? And 2. I saw an instructable on harnessing energy from the ground and air, using a capacitor. Do you think that it can be used to bring batteries back to life? Thanks in advance!

azmatanwar (author)2011-07-25

Can we use this trick on 12 V car battery??? regards.

3of5 (author)azmatanwar2015-11-22

I realize I'm 4 years to late to be giving you an answer, but here is something incase you need to ask it again:

Yonatan24 (author)azmatanwar2015-07-28

Also a little late but, I'm not sure because car batteries are lead acid

LazyH (author)azmatanwar2015-04-06

probably a little late but in case you or anyone else is interested in removing sulfur from a car battery you have to realize that it's the quick pulses that desulfate the plates on a car battery, and doing so repeatedly often while charging, so a few longer and weaker pulses from a capacitor won't make much of a difference to the sulfur on a car battery. There are a few instructables on car battery savers as well though and a quick Google search will give back a ton of results.

zain_de (author)2015-06-18

i had a 160uf 330v capacitor from my old camera. i had dead Nimh battery and i made a direct circuit with capacitor and good alkaline cell with dead cell and i think i burnt my capacitor..... it smells bad. Please help me...

paul1212 (author)zain_de2015-07-01

jennyxls (author)2015-01-30

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.

taterz (author)2014-05-07

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.

vlre (author)2014-05-01

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...:-(

JaredN (author)2013-09-28

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.

crazypj (author)2013-09-15

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?

polkapolka (author)2013-07-24

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

biochemtronics (author)2013-07-08

I use jumper cables and a car battery. Works everytime.

Melibokus (author)2012-12-15

Hello, thats fine. My problems are 3 NiCd 18V accus. From a screwdriver. How shall I refurbish these. Otherwise they are poison rubbish.

luig (author)2012-02-13

hey could this be used on bigger batteries eg. NiCd rc batteries 7.2 volts.

timmartha (author)2009-07-02

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)timmartha2009-10-04

You mean short out the battery 15 times with a car battery?

timmartha (author)Plasmana2009-10-04

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)timmartha2009-10-05

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

bricabracwizard (author)Plasmana2012-01-07

I think he meant car battery charger, not the battery itself. This works I used it to bring back an old dead cordless drill.

timmartha (author)Plasmana2009-10-05

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)timmartha2009-10-06

Thanks for your advice, I will try that when i get more dead batteries :-)

matstermind (author)Plasmana2010-04-04

do you know if that would work with electric scooter batteries?

timmartha (author)matstermind2010-04-06

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.

matstermind (author)timmartha2010-04-06

ok, thanks

phil galati (author)2008-11-29

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

wdelgenio (author)phil galati2009-02-09

I didn't know you could fly an entire plain remotely.

lol, I thought the same thing!

Plasmana (author)phil galati2009-02-11

Thanks for your nice comment! :-)

About This Instructable




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