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Shop Tips #1: How to breathe new life into dead cordless tool batteries

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Blog entry by DonnyBahama posted 1109 days ago 3835 reads 3 times favorited 14 comments Add to Favorites Watch
no previous part Part 1 of Shop Tips series Part 2: A couple of "best practices" while cutting pieces for a project »

I have two Ryobi 18V kits (drill, circular saw, sawzall, dustbuster, flashlight). I got the 2nd kit (which came with 2 batteries & a charger) for the same price as 2 batteries – so now I have spares of all my cordless tools!

Recently, one of the batteries stopped taking a charge. There’s a somewhat famous video out on the interwebs in which a welder is used to zap a dead cordless tool battery back to life. I don’t own a welder but I read elsewhere that any relatively high current DC power source could be used effectively. So I plugged in my 12V (car) battery charger and set it to its highest setting (in this case, 6 amps). Holding the negative clamp against the (-) terminal on the battery, I then very briefly tapped the positive clamp against the (+) terminal on the battery. I then popped it into one of my flashlights. It was supposed to get brighter, but it didn’t. I tried again. Same result. I tried a third time, this time holding the positive clamp to the battery’s (+) terminal for a half a second or so. When I tested it in the flash light, it was clearly brighter. I pulled it out and increased the zap duration to about a second. Even brighter. I then stuck the battery into the charger and left it over night. The next morning, it had a full charge – and a strong one. That battery is now as strong or stronger than any of the other three.

Apparently, the science at work here has to do with the build-up of some sort of crystals inside the individual battery cells. Over the life of the battery, these crystals eventually form a bridge from the positive terminal (of an individual cell) to its negative terminal. This renders the cell incapable of taking a charge. The individual battery cells are 1.2V, so in the case of an 18V battery,there are 15 individual cells. Losing one cell leaves you with 16.8V. Losing 2 or 3, you’re down to 15V or less. Once you lose enough individual cells, the remaining good cells don’t have a path for properly charging. (And in some cases, the charger can sense a problem and refuse to charge.) What the high current DC zap does is liquefy those crystals, restoring the individual cells and making the whole battery good again.

IMPORTANT NOTES:
1. This is for NiCD batteries ONLY – DO NOT try this with LiON batteries. Some people say it works with NiMH, others say it doesn’t (or advise against doing it.) If you have a dead NiMH battery, do some googling and use your own judgment.
2. Reportedly, this can make your battery EXPLODE, so wearing protective clothing (and eye protection) is strongly advised. (Personally, I’m inclined to believe that if something is going to blow up, there’s likely to be some heat that will build up as a warning sign. My battery didn’t show any sign of heating up and everything went smoothly. Your mileage may vary.)
3. I am providing this for informational purposes ONLY. DO NOT actually do this. There. If you try this and your battery blows up, I TOLD YOU NOT TO, so don’t blame me.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451



14 comments so far

View DonnyBahama's profile

DonnyBahama

215 posts in 1127 days


#1 posted 1109 days ago

I noticed this afternoon that another of my batteries is failing. This time, I’ll shoot some video and post it.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451

View Kevin_WestCO's profile

Kevin_WestCO

60 posts in 1143 days


#2 posted 1109 days ago

Do you know how they have been using welder to do the same thing? I have a couple 18v Dewalts that are failing…

Thanks for your post!

View DonnyBahama's profile

DonnyBahama

215 posts in 1127 days


#3 posted 1109 days ago

It’s exactly the same method, but the voltage and current are both quite a bit higher, so you don’t want to hold the positive terminal on there more than a fraction of a second – just a quick tap & pull it back. If you’re no sure which is positive and which is negative on your welder, just measure it with a voltmeter. If it measures -VDC, then you’ve got them reversed.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1711 days


#4 posted 1109 days ago

Just a note …... if you loose one cell the battery is dead
they are connected in serie and not paralel …. its the same as the old chrismaslight chains
unscrew one of them and the hole chain is black

Dennis

View DonnyBahama's profile

DonnyBahama

215 posts in 1127 days


#5 posted 1109 days ago

Thanks for the input, Dennis. Of course they are connected in series- otherwise all those 1.2V wouldn’t add. As I understand it, though, those individual cells that “go bad” will still conduct (keeping the chain intact) – they just won’t take a charge.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451

View Kevin_WestCO's profile

Kevin_WestCO

60 posts in 1143 days


#6 posted 1108 days ago

I’m going to try that. I’ve had one in the tool box that has been weak for a while. Hopefully it works.

Since they are in a series one individual cell can go bad without causing any problems to the battery other then voltage loss. As long as there is still continuity between the cells, all but one could fail and still take a charge. Weak and short in duration but they will still charge.

View gfadvm's profile

gfadvm

10533 posts in 1286 days


#7 posted 1108 days ago

Donnie – I dont think I want to be in the same county as you when you zap that battery with a 220 volt arc welder! Theres a big difference between a 6 amp battery charger and an arc welder. Be careful man as I enjoy your posts and dont want to lose you.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Peter Oxley's profile

Peter Oxley

1426 posts in 2470 days


#8 posted 1108 days ago

I know a guy who swears by throwing them in the freezer overnight … I haven’t gotten up the courage to try that one.

-- http://www.peteroxley.com -- http://north40studios.etsy.com --

View DonnyBahama's profile

DonnyBahama

215 posts in 1127 days


#9 posted 1108 days ago

gfadvm- from what I've read, the output of a welder is 24VDC 600 kajillion amps, so while the voltage isn’t that much different (only double), the current sure is. I don’t own a welder and probably wouldn’t try this with a welder if I did (who am I kidding? I’d be all over it!) but I’ve seen the video and read many positive reports from people who’ve done it.

@Peter Oxley- I’ve tried that with standard NiCD (i.e. AAs, etc.) cells and it didn’t revie them. Since our tool batteries are typically made up of lots of AA/AAA cells, I highly doubt it’s an effective measure for reviving a dead battery. I suppose it might work as preventative maintenance (maybe the cold inhibits the growth of those crystals), I don’t know.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451

View gfadvm's profile

gfadvm

10533 posts in 1286 days


#10 posted 1108 days ago

Let me know when you try the welder. I’ll be in the tornado cellar!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View oldcans's profile

oldcans

20 posts in 1610 days


#11 posted 1107 days ago

I tried it but I didn’t remember the part about a brief tap. I hooked up an 18 volt Dewalt for several minutes to a 12 volt 12 amp charge then charged it overnight on the regular charger. I think it did some good since it does turn the drill I tested it with at half speed (I tried a battery that would not charge at all). There is a person on the local craigslist that advertises reconditioning for about half the price of new. It makes me wonder if he performs the same trick.

-- Dan, quartersawn oak = oak with stretch marks

View DonnyBahama's profile

DonnyBahama

215 posts in 1127 days


#12 posted 1107 days ago

12 amps for several minutes?! Lucky it didn’t explode! Makes me a lot less worried about using a welder, for sure!

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society - http://lumberjocks.com/topics/29451

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1711 days


#13 posted 1107 days ago

don´t take too easy with safty on this with battery´s
have seen a carbattery explode when getting power from another car to start the car with (both 12 V )

Dennis

View David Grimes's profile

David Grimes

2072 posts in 1236 days


#14 posted 1107 days ago

It’s called spiking a battery, with the ultimate goal of removing dendrite crystals by “spiking” the battery with an electric current.

Most recommendations are to use a trickle charger for a few (2-3 light) taps on the positive side followed by one no more than three (3) seconds duration connection.

Then test the battery for full charge (with meter or charger).

Repeat until fully charged.

I would try this, but all seven of my Craftsman C3 batteries are fine. DeWalt and Ryobi, where are you when I need you?

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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