Rebuilding A Cordless Drill Battery Pack

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2[H]4U
Joined
Jun 12, 2001
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3,885
I have a craftsman (Sears Crapsman :rolleyes: ) cordless drill and the battery's (It came with two) are of pretty much no use anymore because of the Nickel Cadium Memory Effect (Stupid Drill bought it in 2005 so I would think it would be new enough to use another battery type)

First of all how do I open the thing? It uses what looks like a Torx screw with a piece in the middle

here are pictures I took of the screws and battery pack

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IMG_0845.jpg


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Its a 12Volt drill and I can solder ok (Not the best at it)
and once I get it open what do I do?

1. Figure out what type of battery to get
2. Figure out how they are wired (Series Or Parallel)
3. Figure out how to charge the new rebuilt pack
4. Is it worth it?
I really like the drill i have been using it as a wired drill for now (Hooked it up to the 12 Volt line on a PC Power Supply)
 
Depending on the price of a replacement battery compared to a DIY solution (which definitely is possible), it may be worth it :)

If you can't get new batteries for this drill anymore, then I would definitely give it a try. It's relatively easy. You know the voltage the drill expects already, NiCd load drop-off curves are known (though since it's a drill, anything close enough to 12V should be okay), so it'd be more or less a matter of cramming as much capacity into the available space.

As for the charge circuit, NiMH charge circuits are relatively easy to construct, depending on your demands (timer-based or intelligent).

Good luck! :)
 
Almost all of those NiCd battery packs use "Sub C" batteries, though I've seen AA and 5/4SC used.

Haul the thing apart and measure the dimensions of the batteries inside. But, to give you an idea of what you'll be paying to rebuild the thing, ten 1.2V, 1300mAh SubC's from Digikey cost $33. NiMH's will run you $57. Of course these are Digikey prices, you might be able to score a better deal off eBay or some miscellaneous "battery warehouse" style website.
 
Heheh......

I love all the metal dust/shavings around that torx screw.....havin fun I see... :D

That's called a 'torx security' screw.You can get a proper bit for it at a tool store for a couple bucks.
 
I hate to discourage a potentially combustible or explosive hack, but with lithium ion batteries available now, why not get a newer drill and batteries? Is cost an issue? Cordless tools aren't designed to last for more than a few years. Newer tech makes the older ones obsolete. My ridgid lithium ion drill has an LED light, as do many other drills now, and it's something I'd be frusterated to be without now. Most new drills are 18v as well, so you get more torque.

Woah, 3-6 hours charging time? I just noticed that on the bottom of the drill. My ridgid batteries charge in 30 mins.
 
Keep in mind, NiMH batteries are generally not made to support the output load that a NiCad will. You'll either want to look into another NiCad pack or possibly a high load Lithium pack.
 
Oh, another thing I noticed... "charge time 3-6 hours". Then I looked up the charger... BAH. Stupid piece of plastic that probably weighs 5 grams, and has a single red LED on the thing.

Memory effect didn't kill the battery, overcharging did. These stupid little chargers just drive the saturated voltage output of a wall wart directly into the NiCd's without any charge control - the same stupid method used by rechargeable vacuums, rechargeable razors and other cheap crap. Even if you rebuild this battery, the charger will probably just kill it again.

If you get another drill, make sure its charger has a charge status LED. Not just the single red LED that appears when you drop the battery in the charger, but a bicolor "charging, charged" LED or a pair of LEDs. At least in this case it has a proper charge controller.

Alternatively, you could rebuild your drill and build yourself a MAX713 or microcontroller-based NiCd charger. This way you get a faster charge and your battery lasts longer too. However, new batteries + new charger will likely be more expensive than a whole new drill...
 
i suggest ryobi tools in the future. maybe a little more expensive but they are great
 
Ryobi is disposable crap. Craftsman aren't bad for 18-19.2. DeWalt still are the best. But the question was about rebuilding a battery pack.

1) The security torx screws are not a common size, it's like a T7 or something IIRC.
2) The batteries are sub-Cs, usually around $2 each (check here or here)
3) A 12 volt pack will have 8 cells, so it will run you around $16, or $20 with shipping
4) The internal connections are welded (not soldered) Cu-Ni (copper nickel) tabs. They can not be removed without destroying the existing cells, which is nasty business with NiCad, and they can not be re-assembled *properly* without a battery tab welder. I.E. not worth it. Some people say they can solder the tabs back on, but there's risk that the battery performance and life will be seriously degraded by the time you get the cell hot enough to wick solder.
5) The batteries are packed using a thin mica film to keep the hot parts of the plastic. I've never understood why they use it, but if you don't find a piece of thin cardboard or eqiv. to replace it with the cells will wiggle around.

Okay, okay; the moral of the story is I've rebuilt two Craftsman 19.2 packs (one with stock nicads and one with LiPo), and it's just not worth it. The old style 19.2v drills are $80 these days, which includes two batteries and a 'smart' charger (AND the drill...). Recycle the old pack, buy a new drill.

JSD
 
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