Battery Question

[atrowe]

I've got an old 18 volt cordless drill and the battery won't hold a charge for longer than 5 minutes or so. I went to Lowes the other day and they wanted $70 for a replacement. It's an old drill, and I have a better one anyway, so I don't really want to spend $70 bucks on a replacement battery. I took apart the battery and there are a bunch of cells inside. I was wondering if I could take out the old cells and put 12 rechargeable AA cells inside. I'd probably use NiCd cells because that's what were originally in the battery. Also, I understand that NiCd cells have the advantage of being able to discharge their entire energy supply very quickly, which NiMH cannot. My question is, would this work? Would I need to worry about burning out the drill's motor or the batteries themselves during charging? Also, would I need to wire the cells in series or parallel? Or am I just wasting my time and I should throw the drill away?

 

[dkozloski]

Check your old cells one by one with a VOM and cull out the dead and shorted ones. The cells will have straps welded to their ends for interconnection. These can be pulled loose with pliers. Go to your local RC hobby store. They will have more-suitable, solder in replacements. Be careful while handling the disassembled battery pack as ni-cads, when shorted out, can build heat and burn you or explode.

 

[Evadman]

standard AA batteries will not have a high enough output to get the torque you need.

What 18v drill?

I can get a 12v firestorm from Home Depot and ship it to ya for $39.

 

[aka1nas]

The main diff between NiCD and NiMH is that the NiCD requires full discharge before recharging or it will get a memory effect. NiMH does not have this requirement. If the battery charges off a proprietary NiCD charger, then I would stick to NiCDs(I believe that the 2 battery systems do charge slightly differently with one requiring a constant voltage and the other leveling off as the battery charges).

 

[zephyrprime]

Your battery pack probably uses sub-c size batteries. Batteries of this size are readily available online at specialty battery retailers so try your luck out. I believe that Batteries plus also sells them but they are rather expensive there.

Nimh batteries are superior to nicads in every way. They have higher discharge power, not less, than nicad. They're even cheaper to make I believe (but manufacturers charge more anyway

If your charger is a slow charger, then you could *probably* use nimh batteries rather than nicad. If your charger is fast or smart, then nimh's would be incompatible.

 

[atrowe]

I checked out BatteriesPlus' website and they've got a bunch of sub C type batteries ranging from 700 to 2000 MaH. 1.2 volts each. This looks like the type the drill uses. I've got a bunch of AA NiMH batteries rated at 1700 MaH. The drill also has a slow charger (8 hours, I think), so I don't see why it wouldn't work. I'm gonna tinker around tonight and see what happens.

Evadman: I don't know what brand drill it is. I'm at work now and the drill is at home. It's a pretty cheap one. Not a name brand. That's why I don't want to spend 70 bucks on a new battery. Someone gave it to me as a gift a few years ago. I've got a 14.4v FireStorm drill at home and I like it better anyway.

 

[Evadman]

Most Dewalt cordless drills now use NIMH batteries. You should be able to pickup the batteries from another source, and use a dewalt charger.