Part1 - How to revive / rejuvenate / fix a bad rechargeable NiCd battery for cordless drill

** THIS WILL ONLY WORK FOR NICD BATTERIES - DO NOT DO IT TO NIMH OR LION **
This video will show you how to fix a bad or old NiCd battery for your cordless power tools. You need to have a power source that is double the voltage of your current battery. So if your battery is 18V, then you need a power source at 36V. You can use other cordless batteries and connect it in series.

The procedure is this:
1) let your bad battery drain to no voltage
2) connect the (-) lead of the 36V to the (-) lead of the 18V battery
3) quickly tap the (+) lead of the 36V to the (+) lead of the 18V battery, and repeat this quick tapping for 6-7 seconds, then STOP tapping it
4) you can use a multimeter to check the old battery and you should see a voltage of what that battery is rated for
5) now let the old battery sit for 15 minutes so the cells inside can cool down
6) put the old battery in the proper charger and let it charge fully
7) the battery should be as good as new
8) if it's not, you can repeat the above procedure couple more times

Category:

Howto & Style

Tags:

• fix
• revive
• rejuvenate
• recharge
• nicd
• failed
• dead
• cordless
• drill
• tool
• ryobi
• makita
• dewalt
• rigid
• black
• decker
• sears
• rechargeable
• charge
• power

[stevenwrose]

Great video! Clever use of the good batteries. I found this after the fact, but will use it on other batteries. I had a Makita 9100 (probably 15 years old) that was down to 5v (normally 10, 8 cells). Prying off the lid revealed that some cells were shorted. I shorted the terminals of the battery with quick pulses, as you mention, and there was enough amperage in the remaining good cells to blow out the internal shorts in the four dead cells! Thanks for the video. Aloha, Steve

[dial2fast]

@stevenwrose Mahalo!!

[photoman2004]

Awesome idea! How well/long have those batteries held up after the fix?

[dial2fast]

@photoman2004 The ones I fixed are still working as of today. However I don't use/charge on a weekly basis.

[roguefate666]

I was able to get one of my 14.4 Ryobi NiCd batteries up and running. I was able to get a decent charge into the second one use this "surge" technique. Right now I have it on the charger to see if it will hold a charge. Hopefully it will but at least I've got one of my guys online again have use of my cordless drill again. Yay!! Thanks for the information.

[dial2fast]

@roguefate666 Thanks for the update. Good you got at least one going.

[stevenwrose]

@chuckyg0409 It is the current from the external source that is blowing out the shorts (probably tiny filaments) in the bad cells, enabling them to take a charge again. Your charger may measure 50V open circuit (a meter places a very tiny load on the charger), but the amount of current it puts out is limited (as it must be to charge the batteries properly). The source used in this video can deliver amperes instantly. Check Understanding Electricity at steverose period com. Aloha, Steve

[dial2fast]

@geardriven I am not familiar with the DeWalt battery.Usually the tool will only have 2 contacts. From there you can try to do a quick charge on the battery and immediately use your meter to measure those 2 contacts to see if you get any voltage to tell which is positive or negative.

[geardriven]

@geardriven OOPS! The battery does have Ni-Cd on it! Didn't see it the first time.

[geardriven]

I have a DeWalt 14.4v battery that will not accept a charge. I'd like to try this but how do I tell which prong is POS? Also, nowhere on the battery does it state what it is. Whether NiCad or otherwise. Anybody know?

Great video BTW!