Reconditioning tired Ryobi 18v Ni-Cd battery

[mickyd]

The topic of reconditioning Ni-Cd batteries by 'zapping' them isn't new. It was discussed in this thread. I have 3 Ryobi's that are shot and at $30 a pop new, I decided to first try the 'zap' method vs. buying new.

My newest battery was just over a year old and when fully charged, wouldn't last but a few screws / saw cuts. There was virtually no torque left to it. I could stop the drill chuck by holding onto it with my hand.

One EE in the group, who's name will be withheld in the event of catastrophic failure, suggested that rather than 'zapping' the battery pack as a whole, open the pack up and 'zap' each cell individually. The reason has to do with how batteries connected in series (positive to negative to positive to negative etc. through all cells) accept a charge.

Here's the process used. It was a breeze with initial positive results. Abusive testing tomorrow.

Opened up the case. Six screws. "RED X" = not a screw hole.
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Press down on the terminal while pulling up on the cover to remove it.
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Remove locking clips
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Pull battery pack out of housing. This exposes the fifteen individual 1.2v cells.
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Remove insulating cardboard layers on top and bottom to expose + / - battery terminals. Note: There is a double sided adhesive tape on the surface of the batteries that can be left on.
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Continued in next post

[mickyd]

Looking at the individual cells, flat end is negative, protruding end is positive.
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Number each of the cells so that you can keep track of which ones you've done then connect an alligator clip lead to the metal conductor that connects the battery to it's neighbor. Black will go to the flat end of the battery, red to the opposite protruding end.
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Set up the meter so that you can monitor your progress.
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Hook up another set of leads to a 12v power supply (connect to you car battery with it still in your car if you want) red to positive, black to negative, and clip the positive lead to the one on the battery pack. DON'T HOOK UP THE BLACK LEAD FROM THE POWER SUPPLY TO THE BATTERY PACK. Instead, hold it in your hand and just touch it up against the black lead alligator clip connected to the battery pack as if striking a match and break contact immediately while observing the volt meter. When the lead contacts, it will create a spark and you'll notice the voltage will rise instanteneously then immediately start to drop off once contact is broken. I would strike it again and release when I saw the voltage reach ~1.4v. Again, the voltage drops as soon as you break contact.
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Repeat this same procedure for each of the remaining 14 cells making sure to connect the black lead to the flat (-) end of the cell and red to the protruding (+) end of the cell.

After this, I reassembled the pack and slapped it on the charger. It took a total of 3 hours for the green light on the charger to come on. Normally, with a new battery, it takes only an hour. I installed the battery pack in the drill and tried it out. Good news is that I could NOT stop the chuck from spinning with the hand like I could previously. It definitely had the torque of a new battery. Tomorrow, I'll run it through the paces and see how long it lasts while closely monitoring it's voltage.

[horologist]

Mike,

I've heard of this procedure but never tried it or was even sure it wasn't some sort of urban legend. Thanks to your careful investigation we will shortly know the truth. I am looking forward to seeing your results.

Troy

[JPG]

Mike,

I've heard of this procedure but never tried it or was even sure it wasn't some sort of urban legend. Thanks to your careful investigation we will shortly know the truth. I am looking forward to seeing your results.

Troy

This can have some success, but can be unsuccessful if the cell(s) are too far gone(total short). The zapping can sometimes leave them leaky(resudual internal short). Works best if it serves as a method of culling out the errant cells so as to have only good cells in the battery(requires ripping out the bad uns and soldering good uns in their place). I anxiously await Mike's torture test results.

FWIW he has some better odds since all the cells were totally depleted when he started. If the 'depletion' was due to small whiskers, the zapping should be mostly successful(except for the cell(s) originally causing the initial short life 'issue'.(those are the ones I be 'anxious' about!)

[friscomike]

Howdy,

This technique can work. I performed the same technique on a pair of 12V B&D drill batteries that were completely dead and would not hold a charge. I revived them and they have worked well for over a year after the sparking. I used a battery charger previously used for my jon boat's battery.

Have fun,
mike

[mickyd]

The initial verdict is in!! The reconditioning method used above WASN'T effective BUT.....that just means plan B is needed, just don't know what plan B is right now.

When I put the reconditioned battery pack in the circular saw and tried making a cut, the battery pack discharges from 20V to about 16V after making one 2" inch long by 1-3/4" deep crosscut in some poplar.

Next step will be to disassemble the battery pack and look at each cell individually.

[JPG]

The initial verdict is in!! The reconditioning method used above WASN'T effective BUT.....that just means plan B is needed, just don't know what plan B is right now.

When I put the reconditioned battery pack in the circular saw and tried making a cut, the battery pack discharges from 20V to about 16V after making one 2" inch long by 1-3/4" deep crosscut in some poplar.

Next step will be to disassemble the battery pack and look at each cell individually.

3 bad cells! Maybe more(longer discharge will tell that tale).

[robinson46176]

I haven't seen it mentioned here but the original instructions for this that I saw said to put the battery through a full recharge cycle before zapping it. Was that done here? I have no idea exactly what that is supposed to accomplish. It may be valid or it may be like standing on one foot while zapping.

[horologist]

Mike,

Good work. If you have a few bad cells as JPG says then I wonder if the remainder of the cells are going to be much better. Would it be better to replace all of the cells? Are these things readily available in small quantities? I know there are people who advertise reconditioned lap top batteries for about half the price of new so it is possible.

Troy

[dusty]

I began this process yesterday. I find that I have three or four cells that measure 0 volts. Assuming that those cells are shorted, this process may not work. That is yet to be seen.