Bring Dead Ni-Cad Batteries Back to Life




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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?

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...

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!

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

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

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

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!

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?

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360 Discussions


6 years ago on Introduction

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.

3 replies

Reply 7 months ago

Thank you. You are exactly the guy I wait for to comment on something like this before I go anywhere near it. Advice taken. Thank you again.. (oh, I really hope noone is tempted to try this with laptop batteries anyway. its kind of like putting spray paint cans in the oven to se how much paint is left in them. In the end, it doesnt really matter....I know its been 6 years but time isnt the same on the internet is it?


Reply 3 years ago

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?


Reply 2 years ago

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.


10 months ago

Wow, this is exactly what I was looking for, thank. I have one question..since this technique is not for charging the battery, is polarity important? The reason I ask, is that I've used hundreds of disposable cameras for various purposes, they're a wonderfully simple, effective and easily accessible little high voltage source. The problem is that they are getting hard to find because most places like Walgreens etc photo departments no longer develop them. What I use now is the capacitor and charging circuit from an electric fly swatter. They're only $3 at harbor freight.
Would that work? If so, I may go bigger, just for fun and use my salt water's a

Capt Caveman

1 year ago

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?


3 years ago

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.

1 reply

Reply 2 years ago

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.

Less Opinion

2 years ago

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.


Lee WilkersonKevinD6

Reply 4 years ago

My NiCd charger says it will also recharge NiMH batteries.

ΧωρίςΌLee Wilkerson

Reply 4 years ago

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.

Lee WilkersonΧωρίςΌ

Reply 3 years ago

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.


Reply 4 years ago

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.


10 years ago on Step 7

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

4 replies

Reply 9 years ago on Introduction

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....


Reply 3 years ago

Thank you for answering this question!


Reply 9 years ago on Step 7

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


Reply 9 years ago on Introduction

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