Reviving a dead NiCad battery

UPDATED! : I’ve added a photo to the battery terminals, see below.

Recently my trusty Black & Decker Quatro drill/driver/saw/sander started misbehaving.  It’s been great for years and gotten us through a lot of DIY and IKEA modification.  But now it could barely manage to cut a 15cm length of 1cm chipboard.pict0027

Time for a bit of investigation.

I wondered if this was due to the charger not actually charging, it seemed ok, the LEDs lit up but on closer inspection there was a suspiciously low voltage at the charging pins and a distinct smell of “magic-smoke“.  So after a quick trip to the Ferreteria to buy some star drivers (why do they use these annoying types of screws) I could see that there was a very hot and rather charred looking transistor.  Looks like the charger was dead.  I thought about replacing the transistor, but unfortunately the part wasn’t marked and after a lot of Googling I couldn’t find any schematics.  It’s quite an old model and not available any more and plus there’s no knowing what else might have died, so I bit the bullet and bought a new fast charger.

Turns out that the battery pack had died too, it probably died first and took the charger with it in some sort of suicide pact.  A quick search of some online DIY forums shows that this is a common “feature”…  The new charger has a diagnostic “blinky light” that alerts you to a dead pack.


14.4v Black & Decker Firestorm NiCad pack.

The pack is a 14.4v NiCad (12 cells of 1.2v) which should have a terminal voltage of around 14.4v (not surprisingly).  Mine had dropped to just a little over 6v.  Bad. at nearly 60 Euros for a new pack… Very bad. Especially as I had just shelled out on a new charger.

I remembered from my childhood RC car days that NiCads have this problem called crystal dendrite growth.  What happens is that inside the battery crystals form, the crystal conduct electricity so when enough of them have formed they basically short out the battery.  What we used to do in those days was whack the battery across a car battery for a second or two and that’d sort it out.  It burns away the crystals and brings the battery back to life.  Also gets quite hot too! I remember that it works quite well,  not quite as good as a brand new battery but better than you might think.

That’s easy when the battery pack is 7.2 volts and you have a 12v car battery with effectively infinite current to zap with.  Not so easy when you’re living in an apartment with no car and the pack voltage is 14.4volts.

I tried with an 18v 2A spare laptop PSU but it made no difference so it was time for something a bit more adventurous.

Some people have had a lot of luck using disposable camera flash electronics to zap their NiCads.  Here’s an instructable. Others have used welders…

Just so happens I had a disposable camera that I had saved for a project just like this.  It’s a Kodak, not sure what model it is as they don’t print much on the outside. They’re easy to open, especially as I’m not bothered with re-using it, at least not as a camera.

Kodak disposable camera.

Kodak disposable camera.

After ripping it apart the I had the circuit out and made a note of the polarity of the AAA battery (positive end is the spring on the circuit board).  After a quick test to make sure it still worked, using a wooden chopstick to press the buttons, I de-soldered the flash bulb and soldered in a couple of extension wires across the main capacitor terminals.

Flash circuit extracted from camera.

Flash circuit extracted from camera. Flash bulb disconnected. Extension cables soldered across capacitor.

Now I was ready to go.

Note:  This could be quite dangerous.  The capacitor is charged up to around 300V (measured) and when triggered the circuit boosts the voltage again to around 1000V (not that I measured it).  So be careful if you intend to try this. Do not short this across your body, it will hurt and might be life threatening.

Charge up the circuit, listen for the whine, then when the light comes on I disconnect the battery and short the extension wires across the terminals of the B&D NiCad pack, positive to positive, negative to negative.
It makes a loud crack and a small spark!


Battery terminals. Temp sensor connection is not used in my new charger.

The voltage at the main capacitor is around 300V.  There’s no need to actually trigger the flash as such, and I think that it’s probably best not to as that would mean the output voltage would be much higher as it dumps the capacitor voltage into a coil to raise the voltage to around 1000V.

After two tries my battery voltage had risen to nearly 7 volts. So I plonked the battery on the new charger for 10 minutes and the pack voltage had risen to 12 volts.

One more zap and another ten minutes on the charger and the pack voltage had risen to 15V  Hurray!  After an hour on the charger the pack was fully charged and back to normal.  The light even went green when the pack was fully charged!

I’ve been using the drill quite a bit since, putting up curtain rails, and have recharged that pack a couple of times. It definitely seems to be back to normal.  The capacity seems to be up to the same level as before the problem.

Not bad for free and certainly better than 60 Euros for a new pack!

Additional photos

Battery pack opened up.

Battery pack opened up.

Old charger (Now dead) with temperature monitoring

Old charger (Now dead) with temperature monitoring

New charger.

New charger.

Bottom of drill.

Bottom of drill.

63 thoughts on “Reviving a dead NiCad battery

  1. What terminals on the battery did you hook the cap up to? I have 3 terminals plus one plate on mine (like yours) but dont know what they’re all for.

    • Hi Steve,
      The plate is for the temperature sensor in the charger, I’m not sure what the third terminal does. It’s not even used in the new charger I have. But, I don’t remember exactly which is which and I don’t want to tell you the wrong ones. So I’ll check and post a photo on the original post.

  2. Are you sure of the diagram?
    Lookning at my battery the 2 left prongs get inserted into something on the drill, the one on the right (as you look at the photo) does not seem to connect to anything in the drill or the charger. I assume that the 2 on the left are +ve/-ve but I am not sure which.

      • I justgot a voltmeter. The middle prong is the -ve (definitelly as current only flows when this one is touched and it shows +ve values when the -ve wire is connected to it). Since the current flows from both the other prongs, I assume that the one on the left (as you look at the picture marked Temp) is the +ve since the other one, in a wider space, does not seem to connect to anything on the charger or the drill. I guess it must be the earth- what do you think?

  3. Hi Martin.
    The voltage across V+ and TEMP is Zero and the resistance between them is less than 0.5 Ohms so it would seem reasonable to assume that they are in fact the same thing and are interchangeable. I opened the pack case to have a look, but without pulling the cells apart it’s hard to see exactly what is happening inside.

    My old charger, the original chunky one (now dead) used the TEMP terminal plus the small exposed metal plate to monitor the temperature of the pack. Whereas my new charger only connects to the V+ and GND terminals. I opened the new charger up to have a look and there’s an unpopulated connector space on the circuit board labeled “Temp”, I guess they decided not to implement that feature in this version. So that’s why I’ve labeled the battery terminals the way I did.

    My drill, like yours uses the terminals marked TEMP and GND to connect to the battery.

    So I think that you can safely use either V+ or TEMP as V+.

    FYI. I’ve added a photo of my old and new chargers for you to see.

    • I guess that would be about right. My charger, a UK version, is very simple and has no monitoring on it, nor a charge indicator. I was not certain what GND meant ( I am not much of an electrician) so I was not sure if that was the -ve terminal. I guess we meant the same thing.
      Thanks for the replies.

  4. Tried your suggestion and blew up my garage! Just kidding… You saved me about $60 for 2 replacement batteries. I have a car battery charger that has a 50 amp “Boost” setting to start a car if the battery is dead. I used this setting and gave each battery 2 five second shots. They immediately went grom 0.02 VDC to 12.46 VDC. I put them on the charger and it charged them in about an hour. I just pumped 35 gallons of water with the drill and a little drill pump. Drill still had plenty of power to drive a screw into wood 30+ times before I just said F— it and put the drill away. Thanks, Bro. And to think, I almost paid $6-7 bucks for this same info from another web site.

    • Hi Ron.
      You had me there for a second with your blown up garage…

      When I was seaching for information all I could find was those annoying sites that want you to pay before they tell you the “magic solution”. And the Black and Decker site is useless when it comes to any technical information.

      So it was that that prompted me to make this blog post.

      Glad it worked for you.

  5. RE “GND”

    GND is the abbreviation for “Ground”, electrical designation used in north america. Brit-speak equivalent would be “earth”. The grounded terminal is normally the negative one, or in AC circuits it has the neutral polarity.

    • Hi Julian.
      Funny, I’m a Brit myself and have always used GND when referring to electronics, keeping Earth for more serious Electrical things. You are right though…

  6. I just tried it with my dead firestorm 14,4 NiCd (which refused to charge by directly turning on the green led on the charger. Lucky me has a 24V truck (ex army Landrover) so I applied 24V a few seconds to run it hot. I inserted then the battery pack in the charger and it charges again. Let’s pray it will hold it’s charge.

    Great tip. Didn’t know that trick to revitalize old NiCd’s.

  7. Yep a 24v Landrover battery should have more than enough punch to zap a few crystals. Don’t let it get too hot and be careful of spot welding the battery contacts to the battery! I found that out the hard way recharging NiCad packs in my radio control days as a kid.

  8. Just resurrected an 18v Ryobi Ni-cad battery that I’ve had for about 8 years, and it had become dead to the world and wouldn’t even take a charge. I used an old car battery charger that had a trickle mode and a 30amp/50amp quick charge/jump start mode. I used the higher setting, connected the charger to the correct polarity leads on the Ryobi battery, and zapped it three times for about a second each time. Fixed my battery immediately. It took a charge, and then I used it to sink about 150 drywall screws and the thing still seems to have plenty of juice left.

    Of course I was overly cautious when I did this, and had the battery and charger around the corner, and used an extension cord to actually complete the zapping process. Everyone who tries this ought to take extra precautions just in case your battery reacts differently than mine did.

    I suppose the real test will be time, and how long this “fix” lasts – but for now I am very impressed. Thanks to all for the info!

  9. I am confused. So, if I take the camera flash, I hook the + lead on flash to + on battery, and – on flash to – on battery? Then, I hit the flash to zap it (like I was taking a picture)? Thanks.

    • Yes that’s basically it, the spark vapourises the crystals that have formed in the battery.

      You do so at your own risk though so be careful!


      • OK. Thanks. Just one other thing, when rereading your instructions, I should not trigger the flash. Just short the capacitor terminals to the battery?

      • Yes, that’s what I did.
        I don’t think you need to trigger the flash, just short the charged capacitor across your battery terminals.

  10. I used a power supply from a knackered laptop (18V) and I couldn’t believe the Lazarus effect . Brilliant ! catmacey you are a star my man !!!!

  11. A bit more info . I applied 18.8v to a 14.4v b&d firestorm for 10 seconds . It retained over 16v for a minute or so (normal retained voltage with the manufacturers charger being about 0.5 v) after being disconnected . When it dropped below 14v I stuck it on to the b&d charger and it started charging normally . The most awesome tip ever but I don’t think that you need to strip down a disposable camera , Just over-volt it for a few seconds .

  12. Thank you soo much. I have 4 14.4v batteries and before I read this page none of them worked. The only thing I did different was used a jumper pack for junping off cars. It worked great. I already have 2 of them charged. I can’t find them in any store around here, and when they were sold in stores, they costed 35 dollars. So again I say thank you

  13. hi,

    I am going to come across as really stupid here, but I can’t get this to work. I have an 18v battery with the older of the chargers here, but my car battery charger doesn’t seem to charge the battery.
    The charger works, as the other battery charges fine in it. however, when I put the second battery on it goes straight to green.

    Could you just tell me which terminals I connect to the car charger and how long to leave it?

    Thanks for helping a noob…

    • Hi Joe.
      I’m guessing that your car charger is 12v. Your battery pack is 18v so I don’t think that your car battery charger is going to work unless it has a high current fast-charge/jump-start feature. It’s about providing enough energy to break down the crystals, either as low voltage at a very high current such as the jump-start feature that seems to work well for some people. Or as a high voltage, lower current source like my camera flash. One possible solution would be to use jump leads to connect two car batteries in series to give you 24v at a very high current. That might work. But as always, be careful.

  14. Great advise ! Both of my B&D firestorm batteries went dead at the same time, so I couldn’t tell whether it was the charger or even the drill that was defective. I measured the output voltage -no load- of the charger: it was above 20V, so that seemed ok. The batteries were at 2V or so, but the charger (your “old model”) showed the green led (“fully charged”) right away.
    I used a car battery charger as suggested by Ron, zapped for 10 seconds or so, the battery voltage went up and the charger’s red light went on ! On the other battery I had to repeat it a few times, but now it charging well again. Thanks for sharing your experience !

  15. as you look the battery with the orange clip away from you v+ is the left pin on the battery and v- the middle one. the square connection is also v- and it’s attached with the middle pin inside the battery pack.

    • Hi Tom,
      Sorry but I don’t have the 18v battery so I don’t know if it is the same as the one I have. If you have one, a voltmeter would be the most reliable method of checking.

  16. THANK YOU!!

    I tried a similar thing this morning with amazing results. My last 14.4V Craftsman drill battery had died and I searched for a way to revive it since they cost so much to replace. I found your site and started reading the comments about using a car battery charger instead. I used mine on the 50 Amp start mode for a few seconds and that was all it took! The battery is charging up now and already powers the drill fine. You just saved me a lot of money!


  17. Another success story to add praise and thanks to Catmacey for posting this invaluable blog!

    My B@D Firestorm 14.4v batteries were both reading 5V and deemed fully charged according to the green light on the charger. Yet they could not even turn the drill head.
    I simply set up a 12V car battery to some leads and touched them to the drill battery terminals for 2 x 5 seconds. I noticed a tiny spark the first time I touched the terminals, but not the second. No heating was evident throughout this quick process.
    I immediately rechecked the voltage across the terminals – 14.0V ! I put the battery in my drill and it kicked into life and stayed operating until I was tired of waiting for it to die!
    I put it in the charger and as I write this post – it is merrily charging away (red indicator up on charger).

    Many thanks.

  18. And for me too! Two dead Firestorm 14.4v batteries (charge light green, but no charge, did not measure voltage). Put it for 5 sec on a 12v battery charger (6 amp). I saw the charge indicator go back from fully charged to almost empty over the course of those few seconds. Works like a charm again and is charging right now.

    Thanks a lot for the tip.


  19. Great stuff and great comments too!
    But, I am a little confused about the underlying technique here. It seems like the camera flash system will deliver a short but high voltage zap. The car charger will deliver a much lower voltage over a longer period. Seems like very different treatments. Does one work better or effect battery life more than the other? I have heard that zapping Nicads is bad for them (But hey, they are already dead so how bad can it be?) Then what about doing individual cells rather than whole pack? I have 2 dead Ryobi 12v packs so have very little to loose aside from blowing up my garage… oh wait already did that with the home made iron smelter- an awesome project and got some great tool steel before the oxygen lance broke loose and torched the neighbor’s roof. I have since regained most of my vision and the neighbors are just now again talking to me (via the lawyers of course)…

    No seriously, which method is better for the batteries?


    • Hi Malcolm, thanks for the great comment!
      Honestly I don’t know which would be best for the batteries. For my pack the camera flash did the trick.

  20. Just used the car charger method and have to say a HUGE thank you! I have 4 Firestorm batteries that have quit on me in the last year and was going to replace them, now they all work like they are new. I bought a new one and after charging the others I found that I cannot tell the difference in time or power. Again thanks a bunch!

  21. Hi Catmacey. I was about to try to source a bunch of the correct sized cells and get the soldering station set up when I found this thread…….

    I have a AC in to DC out power supply for pushing out some serious Amps to my LiPo field charger. I can set the voltage etc before switching on the DC output. If I want to use that to burn off the crystals on a 14.4V pack what would you suggest a good start voltage and time to keep the connectors “connected”? This advice is without prejudice and I won’t hold you liable for my house burning down, as I’ll probably test it in next door’s empty house while they’re on holiday.

    I take it it’s +ve to +ve and -ve to -ve. (You’d never guess I have an HND in electronic engineering from that statement would you?). It’s like knowing which drawer your socks are in and then shouting downstairs to the better half to find out where they are.

    • Hi Paul,
      I’m sorry to say that I don’t know for sure.

      The help I can offer is that when I used to do this back in the old days with 7.2V nicad r/c packs It’d be with a car battery, so that’s nominally 12V with a very high current capability. So if it was me I’d try around 20V for a second or three but that’s really just guessing…

      And yes, connect +ve to +ve sort of like pushing the electrons back in where they came from…

      Good idea about using the neighbours house… :o)

      • Thinking about it, I can connect my 2 x 12V golf buggy batteries in series and put 24V across the pack, if the power supply approach doesn’t work. I’ll get back to you with the results, or footage of the fire brigade trying to save my garage.

  22. OK, so I finally got round to performing my physics miracle with 2 x 12V golf cart / motorbike batteries in series, and it has worked a charm. Garage still standing, battery life extended by about 500% vs its slightly broken state, which is about 7 holes with a 10mm auger bit through 4×2 structural beams, vs the 1.5 holes it did just before I “fixed it”.

    Great thread, and you saved me £50 ($80) for a new battery.

    I left the 24V battery connected until the NiCad cells were on the brink of being too hot to pick up, but didn’t time it. I may repeat this one more time and see if I can get any extra capacity back.

    Thanks again.

  23. And one more thanks!!!
    My 14.4 B&D battery was showing 6V and the charger wouldn’t charge it (would go straight to green charged light). All I had above 14V was an old 50V AC welder. Put it on the lowest rating (40amp) connected the earth and sparked the +v terminal (a couple of milliseconds I guess)
    Battery was straight back to ~14V and charges fine. I’m laughing!!

    • i did this off a 24v trickle charger (I suspect my recharger’s packed up anyway) and my two batteries went from 6 V and 10 V respectively, up to 20 V. I charged them for about 20 minutes each (by which point they’re getting hot), and will run them tomorrow and see what usage I get out of them, but so far so good

  24. The b&d that have isn’t a firestorm but the battery is 14.4 and has been loosing its ability to stay charged. Might your method work on it?

    • Hi Sam. It’s hard to say for certain as your battery could be built differently. But if it’s a NiCad pack then yes most likely it should work.

  25. Aside from being helpful and impressive, this was inspirational. Just stumbled upon(pun intended) your awesome site while researching ni-cd battery issues, specifically 14.4 power drill batteries. Your tip/method worked like a charm – my revived battery is kickin out 15V even after multiple recharges. Thanks!

    I’m curious, is the formation of the crystals in the battery due to overcharging? Or just inevitable with time?

    Also, FYI star (or Torx) drive/screw heads can handle more torque than hex/phillips without damage to the fastener or the tool, and the head of the fastener can be much smaller for the same required torque. I think we’ll be seeing more Torx being used in the near future.

    • Excellent news about the battery. I’m glad to have helped.
      I don’t think the crystal growth is due to overcharging. I believe it’s inherent to NiCad battery chemistry. Have a look for NiCad Crystal dendrite growth on Google for a better explanation that I could write.
      Thanks for the TORX info. I hate those things…

  26. unbelievable! my batteries were deader than a doornail and now they seem to have come back to life! Amazing tip! I used my car charger in start mode. only 12 v charger, but 225A. couple seconds and presto! different terminals on my batteries though. my charger only has two terminals wired, the same as on the bottom of your drill picture so I used black on gnd and red on temp(v+) as in picture. batteries worked instantly! charging them now on old charger, hoping for the best, but already got my sawzall humming!

  27. Pingback: Black & Decker battery charger fix | OwlBlack

  28. Pingback: Convert a Black&Decker cordless drill to a corded one | OwlBlack

  29. Hi, is this trick will work also for lithium ion battery? I have b&d LBXR20 20v max. Which was dead for 6months. Thanks.

    • Hi Garcilito.
      I’m no expert but no, I don’t think it will work on Li-ion cells.
      They’re a very different type of battery.

  30. Well, who would have believed this, hooked my 2 dead batteries upto my car charger, first one worked after a couple of minutes, second one took a few attempts, but only normal trickle charge and no boost. Brilliant, new drill £125 or battery £30, nearly threw it away so thanks for this.

  31. Hi, made up a lead and hooked up my 18V battery to car while running at 14.4 v for about two minutes, disconnected and quickly put on to B&D charger while voltage still showed about 10.5 and now charge light stays bright green and battery is charging OK. Many thanks saved me $59.00 NZ for a new battery.

  32. Hi,
    Just a note to say a big “Thank You!!”
    Had the same problem with the 14.4v batteries on my B&D Firestorm cordless. I had bought a new battery in 2012, and used it very occasionally, while leaving it on the charger when not in use. Tried to use it a few weeks ago, and nothing! Wouldn’t charge, voltage around 6v. Was about to buy a new one, thinking perhaps a 6 year life cycle was probably the best one could hope for with these batteries. Then I came across your article!
    I used a car battery charger, set at 10amps, and zapped it for 10 secs. Repeated for another 10 secs. Voltage went from 5.6v to 14.4v. Then left the battery in the charger overnight. Following morning, the voltage was 16.21v. Used it in the drill for a few minutes, and the voltage was still over 16v. Absolutely amazing.

    Again, thanks a lot.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s