Repairing NiCd Battery


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Old 09-24-06, 04:43 AM
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Repairing NiCd Battery

I'm repairing a 14.4 volt NiCd battery for my Craftsman drill and am starting this thread to get some input, and share my thoughts.

I read all the posts to the thread named "Bad battery or bad charger", and the post in there from imagineer (12/8/05) prompted me to try this repair -- plus the fact that Sears doesn't sell a 14.4 battery for my drill, and my online search resulted in finding one at lowest price of about $45.

Anyway, I took the battery apart by removing 4 screws. There are 12 small batteries inside (some net research taught me that these are tabbed (meaning there is already a piece of metal connected to each end) SC (as versus C type) type batteries). They are each marked with 1500 mAh.

I tested each cell with a DC voltmeter (touched each end of battery with volmeter probes) and found 8 have 0 volts, and 4 have about 1 volt. So I figure I need 8 new ones.

I searched the net and found I can get a pack of 10 SC size 2100mAh batteries with tabs from batteryspace.com for $21.95 plus shipping. The other place I found was megabatteries.com where I could buy eight 1500mAh SC batteries with tabs for $16.72 plus shipping. If anyone knows where I can get a better price please let me know.

One other question re the above: it doesn't matter if I mix 2100mAh batteries and 1500mAh batteries, does it?

The first thing I'm going to do though is take apart my other 14.4 volt battery (the drill came with two batteries) and see how many dead cells it has. Hopefully I'll get lucky and find it needs 4 or fewer replacement batteries, then I won't need to buy any (I use this drill as a backup for my Craftsman 15.6 volt battery).

Some other things I've learned about NiCd batteries that might be helpful:
-- I fully discharged a 14.4 volt battery then put it in the freezer overnight after reading on the net that this might help. Then I charged it for a day. This DID NOT WORK. Battery was still basically dead.
-- I fully discharged (clamped drill trigger fully on for about an hour) a weak 15.6 volt battery (first time I had fully discharged it) then recharged it. THIS WORKED. Battery seems to have been rejuvenated. I now plan to fully discharge my NiCd batteries about one a year.
 
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Old 09-24-06, 07:08 AM
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Maybe I can answer a couple of your questions. You do not want to mix batteries with different capacities. If you mix 1500mAh with 2100 mAh, you will have problems with proper charging. Either the 1500's will get overcharged, or the 2100's will not get properly charged. Also, it really isn't good practice to add new cells to an old pack. Yes, it works and will get the pack where it can be used, but often the other cells have lost most of their capacity. It's like tearing down a 200K mile car engine, and just replacing the one bad piston.

Also, when discharging, you don't want to completely discharge the batteries. You should stop discharging when the voltage reaches .8 to .9 volts per cell. For a 14.4 pack, this would be between 9.6 and 10.8 volts when discharged.

There is a lot of useful information at rcbatteryclinic.com. The site deals mainly with applications for radio control devices, but the basics are the same for power tools also. It's good reading for anyone with rechargeable batteries, no matter what they're used in.

Nashcat
 
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Old 09-24-06, 09:54 AM
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The problem that defeated me in this type project was attaching the stainless steel strap to the next battery as I did not have a spot welder and soldering was not successful so figure how you will make the attachments before you buy batteries.
 
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Old 09-24-06, 10:24 AM
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Had the same problem with my Ryobi 18v drill. The batteries were fine. It was just when you torqued the drill, the heat built up too much and burned the connecting strips on the batteries. I took mine apart and, of course couldn't solder the stainless, so I soldered #12 stranded across the broken ones. They have held for a year or so. But Ryobi's are only $40 for a pair, so repairing them cost more than my time was worth. Another thing to consider.
 
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Old 09-25-06, 03:38 AM
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I posted this thread to stimulate some discussion and am pleased to be getting it.

nashcat: I didn't know that mixing 1500 mAh and 2100 mAh batteries is not be a good idea; but I do now. Also, I get the picture re your car piston analogy. This makes me less inclined to replace individual batteries in the pack, and more inclined to replace them all. Re your comment about NOT fully discharging the battery before recharging, I understand what you're saying, but I did get a 15.6 volt to rejuvenate by doing this. Also, I've read elsewhere on the net that this is a good idea. So, I'll probably do this whenever a battery quits performing adequately. Re rcbatteryclinic.com, thanks for the info. I read most of Red's stuff. Based on one of his suggestions, I'm going to start using a timer to charge one of my batteries 1 hour a day to keep it fully charged, and to extend it's life. My practice has been to put them on the charger for a day or so, then remove. But, the older batteries wouldn't hold the charge, so when I went to use them they'd be too weak. The timer idea should solve this.

phord: Good point. I was going to test soldering to the tabs before buying. I'm wondering whether my solder will stick to the stainless steel tabs. I think I have some stainless steel solder, so maybe that will work. Incidentally, I know better than to solder directly to the battery ends.

At this point, as far as repairing/replacing my 14.4 volt battery my best two choices seem to be: 1) buy 12 new type SC batteries with tabs and solder them in at cost of about $30, or buy whole new battery at cost of about $45.
 
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Old 09-25-06, 06:24 AM
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I just looked and for 89.00 at home depot you can get a 18 volt drill , two battries a charger and a flashlight with a two year warranty thats what I would do , same money as two new craftsman battries but you still have a old drill motor and charger
 
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Old 09-25-06, 08:47 AM
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Which is what I did last my my drill crapped out; think I got a drill, flashlight, two batteries and the charger for either $59 or $69 from Sears which was way cheaper than replacing the battery. Kind of sad.
 
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Old 09-29-06, 05:39 AM
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Thumbs up

Just wanted to update this thread to say how I ended up on this.

Home Depot has a sale locally for a Ryobi 18v kit called "The Starter Kit Plus" for $99. It includes drill, 2 18v batteries, circular saw, light, sander, and tool bag. I couldn't resist.

Now I'm wondering what to do with a used Craftsman 14.4 drill that works fine. Hate to just throw it away. I'll give it to anyone here who wants it, and will pay the postage.
 
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Old 10-11-06, 11:41 AM
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Connect a long, heavy lamp cord to the battery terminals inside the drill.. Attach a red and a black clamp, or a cigar lighter plug to the other end.. Toss it in the car or truck, or connect it to a car battery in the shop.. Kinda defeats the cordless feature, but hey, being a 14.4 volt drill, it'll work..
 
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Old 10-11-06, 04:57 PM
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AxlMyk: Neat idea. I'd have never thought of that.
 
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Old 10-14-06, 06:05 PM
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You're welcome.. At least the drill voltage is right for doing that..
I know that NiCads can develop whiskers that short the battery out, and that SOMETIMES they can be repaired by connecting them to a huge, (40-50k-mfd), charged capacitor.. Note I said sometimes...
My question, does the capacitor + go to the battery +?
In case anyone tries this, it should only be done in a closed box as the battery may explode..
 
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Old 10-15-06, 02:01 PM
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Originally Posted by bigfred
Just wanted to update this thread to say how I ended up on this.

Home Depot has a sale locally for a Ryobi 18v kit called "The Starter Kit Plus" for $99. It includes drill, 2 18v batteries, circular saw, light, sander, and tool bag. I couldn't resist.
I bought basically the same kit many years ago, except mine came with a wet/dry dustbuster type vac instead of a sander.
Still works great, though the saw is really only good on a fully charged battery. The drill has enough tourque on a full charge to break the heads off most screws (or send the screw completely through the work).

I used the same idea when my cordless phone's battery died. I just built my own battery pack, which lasts at LEAST 2 to 3 times longer than the stock one ever did.

I'd sure like to try one of the new Dewalt 36v drills..
 
 

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