Attach Wires to NMH Batteries Without Soldering

Welding.

A Batteries Plus store will do it for a small charge -- or sometimes free if you buy enough stuff. The store near Southcenter fixed the broken weld in my B&D battery pack.

Solder your wires to contact pads. Coat the positive and negative terminals with some sort of protective anti-galvanic grease. Use electrical tape to adhere pads by wrapping the battery lengthwise. Make a C shaped lengthwise cover made of sheet metal for the battery. Then use a couple of tie wraps to squeeze the C shaped cover tightly onto the contacts.

Whats wrong with soldereing? Seriously roughen the metal with coarse sand paper then a blob of flux. Then a soldering iron greater than 50W and locally heat enough to get a spot of solder wetted over the roughened area, don't dally and heat the whole cell. Then at your leisure and ordinary iron locally melt a bit of your solder blob and meld with some new solder and the wire. If its for >5 or 10A use then probably not advisable

practise on an old cell first , perhaps

es

r a

Do what Mr. Cook suggests, it is what I frequently do.

Do what Mr. Cook suggests, it is what I frequently do.

+++

I must have done it a few dozen times , admittedly NiCads, but no in service problems emerged over time scale of a few years anyway.

"N_Cook" wrote in news:kavh8v$mma$ snipped-for-privacy@dont-email.me:

Me too. The worry is: that you might melt some plastic internal seperator or similar. NiMH batteries can be stored at -20 deg C so you can put the cells in the freezer beforehand to give yourself a bit more safety margin, but if you are any good at soldering that really isn't required. Whatever you do, don't piss about with a low wattage iron or a fine tip. This is a perfect job for a 100W Weller soldering gun or a catalytic butane gas iron.

I usually roughen up the contact with a fiberglass brush pencil. Its absolutely essential to break through any Nickel plating that may be there.

This is safe enough for NiCd/NiMH but *NOT* reccomended for LiPO cells as you risk turning them into an incendary devicee. [;)]

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I second this. I've done this several times with "non-replaceable" cells in shavers, etc. and have had no failures related to quick-soldering, only the usual slow degradation over time of the cell chemistry.

Tin the wire, emery-paper the terminals, clean, drop of flux, quick solder.

Soldering directly to cells is a bad idea. It's like driving above the speed limit. You won't have any problem finding people who'll swear that they do it all the time. They never get caught... until they do. Go down to traffic court and you'll see the other side of the coin.

I've soldered a lot of NiCd's back in the day. It mostly worked. Except for the few that exploded under charge. And the few that had high self-discharge rates.

And if you're fixing a laptop battery pack, there really isn't room for that solder joint.

You need to find the sweet spot of time and temperature. I found that spot with a DIY battery tab welder. Haven't had any battery problems since.

If you insist on soldering batteries, wear safety glasses. Clamp them down so they won't hit you in the face when they explode. Also helps to have them in a fixed position. You don't have time to fiddle with the cells and the wire and the solder and the iron with only two hands. The separator melts before you get it all lined up.

Did I mention that soldering directly to cells is a bad idea.

Also, use fairly small wire for the attachment and put a tiny blob of solder on the wire to be attached... Then a quick touch with the iron will melt both blobs together. The secret is minimum heat and time, but it is easy to do...... and be sure to use the emery paper on the batt terminals first....

** The industry standard method is a special form of spot welding using two, close spaced electrodes.

You can get NiMH cells with welded, metal tags already attached - and solder these.

Otherwise use ordinary soldering - like thousands do.

For battery packs subjected to high discharge rates, soldering produces reliable, low resistance connections and spot welding does not.

.... Phil

But they're still welded -- which you condemn for high-drain apps:

"For battery packs subjected to high discharge rates, soldering produces reliable, low resistance connections and spot welding does not."

Sometimes it helps to tin the cell using a more aggressive flux than the usual stuff that comes in the solder. Then you can use regular solder to attach the wire.

Isaac

Hi Andy,

I decided to do what the majority of respondents recommended.

I have a 200/260W Weller solder gun and when I gave it some thought, when someone spot welds a tab onto the battery, it creates a momentary hot spot on the battery. The Weller gun can't to worse than a spot weld as long as the time is short and proper preparation is made.

By golly, I had no trouble at all and the results turned out great!

Thanks to everyone and Merry Christmas, John

Oh, yes it can. A spot weld takes a fraction of a second, and the heat appears over a small area.

I hope so. I've seen connections of this sort fail * with the solder blob simply falling off the battery.

• as do spot welds, of course

(...)

Agreed. Over the years, I would solder to cells. Most worked for a little while, but soon crapped out. I did MUCH better with a cazapitor discharge spot welder. or you can build you own:

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A bit more than a fraction of second. See video at: starting at 0:50. I would guess(tm) about 1/2 second for the spot weld. I would also guess(tm) that the heat affected zone on the battery is much larger with the high wattage Weller because of the longer dwell time and larger thermal contact area. When I was soldering batteries, the cell was noticably warm after soldering. When doing the same with a CD welder, it was stone cold.

I test my battery packs with a West Mountain Radio CBA-II. If there's a problem, it will be obvious on the graphs.

Not if you sandpaper the base metal. When I solder to a battery, the solder will wet to the edge of the sandpaper zone, but not into the non-sandpapered area. That implies that there's some manner of coating on the battery case that should be removed with an abrasive before soldering.

The real problems are in high current applications, where the weld turns into a fuse. Power tools are a good example. I did a lousy job of replacing NiMH cells in a Makita 18V driver. After about 4 hrs of use, the pack went to open. An autopsy showed that my welds had fused open. I went to 4 spots instead of 2 spots per terminal, and it was fine.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Well, that sounds like it could be one of those "tales from the cube" stories on the back page of EDN. Tell us more, if you can!

I have a few small tidbits from the sun angle computer from the TIROS ground station.

Jon

Both satellites used dual, identical computers, with one backing up the other. The software was periodically modified or updated, and I was assigned to write the step-by-step instructions for a change.

Although my work was checked by other people, they made the same mistake I did. I assumed that, because one of the satellites did not perform a checksum on that section of program memory, neither did the other one. But it did.

The result was that, shortly after the update, the checksum was performed, wasn't correct, and the computer shut down. For reasons I never understood, the backup computer also shut down. (This was an intentional part of the design.)

I quickly figured out what was going on, and my boss complimented me (which he shouldn't have -- he should have chewed me out). No one was fired, or even reprimanded. I suspect this sort of mistake was not uncommon.

The satellite was "fixed" by sending commands to reload and restart the computers.

You never tested your code in a real setup?