Rebuilding NICAD Battery Packs

On Sat, 11 Dec 2004 20:29:10 -0500, "ATP"
......and in reply I say!:
remove ns from my header address to reply via email
(1) You might look at NiMH cells as replacements. I know this is not in answer to your question, but you get a HEAP more energy per charge.....= longer running.

But buy only a few until you have tested them, and NEVER buy Titanium brand.
I bought 16 from bloody Ebay, and well over half got very hot and leaked when charged -by the charger supplied by the battery vendor-, and also on my other smart charger that had successfully charged many a NiMH until then. I returned them (postage starting to eat into "savings") and they came back "tested"...with the crystalline crap still showing on them!
Never again. Maybe my loss, but I have had one good, and two bad, encounters with dealers on Ebay. Enough.
I never even had a reply on the lack of the 4 x AA NiMH cells I was supposed to get with the charger.
I found a few other complaints about these Titanium brand. They claim a .1% failure rate or something. Well in that case, suck it up guys, and keep sending me new ones until I get decent bloody cells!
Oh yeah, and the rating system. This mob that sold to me had a 98.7% favourable rating. So maybe I am just the unluckiest SOB on the Net.
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On Sun, 12 Dec 2004 12:08:40 +0800, the renowned Old Nick

There's circumstantial evidence that counterfeit Sony NiMH cells are being sold on eBay. They have markedly lower capacity than the real Sony cells.
Best regards, Spehro Pefhany
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and again, maybe third time lucky!
reposted, original seems lost in the aether, apologies if double posted
Larry Jaques wrote:

I've never _re_built packs, but I have soldered them together.
The best way I know is to use a hot hammerhead iron - that's a soldering iron with a bit with two working ends, so you heat both cells at once.
The bit is about 1 inch long and 1/2 inch diameter, and looks like this:
| iron | || | ___||___ | _/ \_ | |_ bit _| | \________/ |
I have turned a few from copper, it's not hard - unfortunately I don't have any now, and I can't get back to the shop before mid-Jan (long holidays!).
You really need at least a 40 watt iron, although it can be done with a smaller one. Wait for it to get hot
People who make up a lot of packs tend to put the cells in the fridge before soldering, use 60/40 tin/lead solder rather than the leadfree type (naughty, but then the cells are full of cadmium ...), and make up a frame so the cells slide easily into the right position. You heat up the ends of two cells at once, make sure they are wet with solder, remove the iron and quickly slide one cell to meet the other.
Then cover with heatshrink for mechanical strength.
Never had a problem once I figured out how to do it - and you could of course practice with the hootered cells first.
It might be worth while googling "hammerhead soldering cell" , some good links there.
Below is a post I wrote in answer to a similar question, not an immediate answer but should have some relevant tips.
However, Tim's point about reversal during discharge sounds relevant. I've always been a good boy and never tried mixing cells tho'. Perhaps you could try to find the set of cells whose capacities match best.
--
Peter Fairbrother


Hawkey wrote:
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On Sun, 12 Dec 2004 06:49:31 +0000, Peter Fairbrother
......and in reply I say!:
remove ns from my header address to reply via email

We have seen all 3 posts, or I have.
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On Sun, 12 Dec 2004 06:49:31 +0000, Peter Fairbrother

Triple-posted.
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On Sat, 11 Dec 2004 08:24:54 -0800, Larry Jaques

Soldering works fine if you use a hot iron (at least 20w) and complete the joint in no more than two or three seconds. Use 60-40 lead/tin solder and an active flux - Bakers soldering fluid or similar killed acid type flux so that you get immediate solder wetting.
Use the solder connection for electrical continuity only.For mechanical retention use epoxy resin assisted as appropriate by duct tape or shrink wrap.
Jim
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Larry Jaques wrote:

I see anumber of suggestions about soldering cells together directly. IMO, this is a very bad idea. I've never ssen a comercial pack done this way. If successful at all, any vibration or mechanical stress would almost certainly either cause the connection to fail or damage the top of the cell.
If you are going to try soldering, use bit of copper braid, preferably pre-tinned such as a bit of the shield braid off a piece of coax. Cut off a length about equal to a cell diameter, tin the very ends and bend in the middle to form a broad V. Tin the cell ends in a small area. Work quickly with a hot iron. solder one end of the braid to the positive end of one cell. Slip a plastic insulating disc over the braid to prevent shorts. Solder the other end of the braid to the other cell's negative then fold to make a compact joint.
And, yes, I do plan to build me a capacitor discharge spot welder but I won't give out the circuit 'til I've designed, built and tried it.
Ted
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On Mon, 13 Dec 2004 00:08:07 GMT, Ted Edwards

Good point there, Ted.

Used desoldering wick works well for that. BTDT, fixed the Bose 501 woofer carbon leads that way twice in the last decade and a half.

OK, I'll give you until (how does next Wednesday sound?) to do that. ;)
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