Restore-Revive-Zap Old Drill Battery

Years ago i watched a video online about a guy who took an old dead drill battery and brought it back to life using a welder.  He said that the reason that the batteries die has something to do with the aligning of the positive and negative poles.  I didn't completely understand it but it seemed to work.

The reason that reviving an old power tool battery is so popular is because of the cost of them.  If you want to buy a new drill that comes with a battery the cost is around $150.  But if you need to buy a new drill battery, that cost $80 on it's own.
fix a dead drill battery, power tool, ni-cad, nicad, lithium ion, dewalt, craftsman, 12v, 14v

At the time i had an old 12volt DeWalt drill with 2 ni-cad batteries.  The batteries were starting to die and could barely hold a charge.  The batteries were practically worthless since they only lasted a minute or two.  But i didn't want to spend $80 on a new battery, it seemed like such a waste.  There are companies where you can send them your old drill battery, they will take it apart and replace the internal pack with new batteries.  The inside of a ni-cad battery pack is actually made up of what looks like several 'C' rechargeable batteries.  Here's a picture that someone else took.
inside of a dewalt drill battery, battery pack, power tool, xr battery

But even this cost around $40 plus shipping.  Still not worth it to me.

So until then i used an old cord drill, it was a pain but it had tons of power.  Then two years ago Karrie bought me a kit of new power tools.  It came with a drill, saws-all, circular saw and light, which all ran off two 18volt batteries.  They have been great the past couple years.  And since then the old DeWalt 12v drill has sat on a shelf.

But recently i bought a new 90amp flux welder from Harbor Freight.  It is just the cheap 90 amp model, i used it to weld up my car mufflers and exhaust a few months back.

chicago electric welder, harbor freight, 90amp

While cleaning up some of the old junk in the basement i saw the old drill and dead batteries.  I took them out and tried putting the batteries on the charger.  By now they weren't just dead, the quickly flashing light said they were defective, they wouldn't even attempt to charge.  So i thought that this would be a perfect time to try out the battery restoring technique using a welder.

The whole process couldn't be simpler.  You basically just turn on the welder, connect the Ground clip to the negative end and then repeatedly touch the positive end with the welding wand.  This creates a small spark from the high voltage coming out of the welder.  Somehow in the process the higher voltage re-aligns the + and - poles of the internal batteries and brings the entire battery pack back to life.

I made a video of the process of me trying to restore the two DeWalt drill batteries.  It might be quicker and easier to watch the video rather then having me try to describe the process.

Fix a Dead Drill Battery - Won't Charge

But for more detail i try and explain what i was doing and why.

The first step was to check the batteries with the volt meter.  Like i said these two batteries had been sitting on a shelf for two years, so it's no wonder that they read 0.00 volts.  But i was able to determine which were the positive and negative poles.  If i had the + and - connected to the volt meter correctly it would read 0.00 volts, if i had it backwards it would read -0.00.  This would be important when i started sparking it with the welder.
checking a battery, power tool battery, 12v, 14v, dead battery

Next i went to the garage and got out the welder.  I set the battery on a table and got ready.  Now normally when you weld the wire feed will roll out wire as you go.  This wire melts and becomes the "weld" to combine your two pieces of metal.  I did not want this to happen so i disengaged the wire feed tensioner, so that no wire would come out.
release wire feed tension on welder

I put on my welders mask for safety, just in case the battery decide to blow up.  Not sure that would even happen, but it couldn't hurt.  Here's the battery about to be sparked, with the two ends of the welder that i would be using.
spark shock fix battery with welder, how to

Then i touched the ground clamp to the negative terminal of the battery and started "sparking" the positive end with the welder wand.  A few small sparks shot up but it wasn't bad.  I did this about 5 or 6 times, until the small wire at the end of the wand melted off.  Then i used a wire brush to clean off the positive end of the battery which was now blackened and had small pieces of wire weld on it.
corroded end of battery after welding, fix with welder

Back down in the basement i checked the battery with the volt meter and it read 0.12 volts.   I was happy that it wasn't at 0.00, but still not sure what that small voltage meant.  
battery voltage after fix with welder, restore, revive, power

Before even putting it on the charger i snapped it into the drill and it actually worked.  Not very much but i was amazed that it had power without even charging it.  So i put it on the battery charger and left it for a few hours.  Another good sign was that it didn't start flashing 'defective battery'.  It appeared that it was charging correctly.  In the meantime i took the other battery to the garage and repeated the process.

A few hours later i came back downstairs to check and the light on the charger was solid, meaning that the battery was charged.  So i removed it and checked it with the volt meter again, 13.69 volts.  I was amazed.  
voltage of new dewalt battery, craftsman, check

I plugged it into the drill and it worked great.  I wouldn't say 100% good as new, probably more like 65% of it's full original power.  But i was still amazed that it took an old defective battery and got it working again.

I tested the drill and battery out and it seemed fine...for a minute or two.   But pretty quickly it apparent that it wasn't some miracle cure.  Yes it did restore the battery, but only a bit.  The charge quickly went away after just a few holes drilled.

So in conclusion, this does work.  If you have a battery that is not quite as good as it used to be i would highly recommend trying this, it might be able to save it and get it back to 100%.  If you have a completely dead/defective battery i would still recommend doing this.  But know that it probably won't bring it back good as new.

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