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Ni-Cad battery replacement

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NutmegCT

NutmegCT

Great Pumpkin
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I often find non-working battery-powered tools and devices etc. at the local recycling center. After cleaning, the device usually only needs one or two replacement batteries for the dead ones in the power unit.

Most of the batteries are Ni-Cad "C" size.

How the heck do you unsolder/solder the batteries from the metal strips that connect one to the other?

Example:

View attachment 25886

The connectors sure appear to be soldered on, but my two soldering irons don't even budge them.

Has anyone ever successfully replaced these batteries in a device? any tips?

Thanks.
Tom
 
You do not solder/unsolder.
Those strips are spot-welded on, rapidly, no heat transferred.
However:
If you order new cells, order them "tabbed", cut or pry the strip off the bad cell, tin and overlap, sweat solder together.
Never solder directly to the cell.
I did this type of work for 20 years.

If you need to get packs rebuilt, look at Cordless Renovations in Iowa.
 
Thanks! never knew that about the spot welding.
Tom
 
If you look closely (like, with a magnifying loupe) you should see between two and four dimples on the tab at the cell. Those are the spotwelds.
Dave
 
Yup-yup. I've had counter-weasels in a battery chainstore tell me I "couldn't solder" AA-size ni-cads in series to replace cordless 'phone batteries (after having DONE it for DECADES). They never saw the tabbed ones. In a pinch, I use #220 wet-or-dry to scuff the untabbed ends and a REALLY hot soldering gun, tin the wire and be QUICK to dab solder on the battery for the connection. Also replaced the Ni-Cad batteries in Nikon MD-3 motor drives with 'em and they outlasted Nikon's $300 complete units. I think I spent about fifteen bucks on the "special order" through a local hobby shop for the tabbed three-quarter height AA's.
 
The issue is, if you know what yer doing, you can use a very hot iron and get away with it. But, not recommended, and I'd never tell someone who hasn't done it to try it.
You can really kill them fast with heat, and the result, if you damage them, may be readily apparent when charging.
 
I've had a battery store spot weld new batteries into my Dewalt packs. The service was actually cheaper than me buying the batteries and doing it myself. The downside was their work didn't last very long. The battery died before some of my year old stock batteries went South. About 8 months ago, I bought some matched cells from Ebay to try DIY. I went with 3.8 amp/hour cells instead of the Dewalt stock 2.1 amp/hour ones. I found that the pre welded tabs were useless because they were mounted on the same plane to eachother. That's fine if you have one battery, but putting 12 in series in a tight case just won't work. I had to pry and grind the tabs off and solder copper strips that I cut from a sheet. I have another six packs that need new cells, but I haven't needed to replace them yet. The 2 that I did work so well, I never find myself without a charged battery. Buying 24 sub-C batteries wound up costing $45 per 14.4v pack.
 
Greg - are you saying you *are* able to solder on to those batteries? If so, how do you do it? Others say it can't be done, at least without wailing and gnashing of teeth.

Thanks.
Tom
 
As Dave says, it ~can~ be done BUT(!) if it ain't done right, things can go south in a hurry when you recharge 'em... it's not a "recommended" practice, I admit.
 
The main thing I was saying is the batteries that come with tabs probably won't have the tabs aligned the way you need them. Soldering wires onto the tabs may make things too thick to get the battery case back together. So far I've had no ill effects from soldering copper strips directly to the cells. I'm not disagreeing with anyone else's comments though.
 
Most of those "C cells" are actually "sub C cells" I have ordered them on fleabay several times to replace various built in batteries and the regular C cells normally wont fit.
If you order them it is easiest to look for batteries with tabs welded on.
 
GregW said:
The main thing I was saying is the batteries that come with tabs probably won't have the tabs aligned the way you need them. Soldering wires onto the tabs may make things too thick to get the battery case back together. So far I've had no ill effects from soldering copper strips directly to the cells. I'm not disagreeing with anyone else's comments though.
Click to expand...
Carefully he responded.
20 years, that's been my business. Bend the tabs over the cell, or a 45 degree (or any other angle), press fold flat. Tin appropriate side, swireat solder, holding top piece down with something like the tip of an xacto.
I have never had an issue fitting them back into where they came out.
 
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