Soldering onto NiMH batteries?

Battery tabs are spot welded because soldering will overheat the seal, and possibly damage the battery.

Do a web search on "solder NiCd" or "solder Nicad", and you'll get lots of opinions on how viable an approach it is and how to do it.

You can get batteries from DigiKey with tabs spot-welded on, then you can solder the tabs together for your application. You'll dump a lot less heat into the battery in the process, particularly if you use a good hot iron that lets you make a good joint quickly.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

How did you open the battery pack without damaging it?

"DeanB"

** With decent soldering iron and some care - yes. ** Solid or stranded or tin plated - take your pick.

** What is found inside normal flux-cored solder is fine.

** No - not unless you take an inordinate amount of time to make the joint.

Warnings against soldering direct NiCd or NiMH cells are not founded on fact.

Manufacturers use steel tabs & spot welding as it is a much quicker method in mass production - but makes an inferior joint ( more resistance) than one made with short, solid copper wires and solder.

..... Phil

I had to snap off a cross-piece to get the battery out, but that does not seem to be an important piece of the construction. I can run the thing off a recharger ok without the cross pieces.

I have opened up surplus NiMH batteries and removed the cells to rearrange them as a battery supply for a different device. I was able to solder them and my new battery pack worked. I didn't have any explosions when soldering but the pack started to leak after about 12 months of use with regular recharging. I threw the battery pack away when it started leaking. I don't know for sure if the resoldering of the cells caused the leaking. The original cells might have been a problem without the tampering. They were sold as surplus.

I consider the effort and cost to be worth it. Less than two dollars of surplus batteries made a working, rechargable pack that would have cost me nearly sixty dollars!

insula

Here is a tip. If you are soldering onto battery terminals, first melt a big blob of solder onto the end using a very hot iron. Then, remelt the solder and stick the wire into it. Works quite nicely, and doesn't overheat the battery too much.

This works well for sets with tabs welded onto them too. Connecting between welded sets is much easier with 'the blob' technique.

Spot welding is obviously better, but I don't have a spot welder...

I agree about RC pack pricing, way too much for what you get.

Another tip is that you can get shrink-wrap tubes to fit the battery pack into, which make them very nice looking, and holds them together well, so there isn't as much stress on the solder joints.

Regards, Bob Monsen

DeanB wrote in news:e2252413-5233-4454-bce5- snipped-for-privacy@e39g2000hsf.googlegroups.com:

I'm a beginner, so sorry if this is a really basic question, but, what is the advantage of soldering them in, rather than using a battery holder?

Thanks!

- Kris

The physical mounting may not lend itself to any available holder, and the mechanical vibrations may disallow it, too (like in a model car or airplane).

Additionally, I don't think you could achieve the low battery-to-battery connection resistance that is required for high current applications without using either soldering or welding techniques.

Bob

--
== NOTE: I automatically delete all Google Group posts due to uncontrolled 
SPAM ==

"BobW" wrote in news: snipped-for-privacy@giganews.com:

Oh, OK, thanks!

- Kris

The cells I used were of a flatenned box-shape [90=B0 corners], (about

1cm=D72.5cm=D76cm) I think they might be called prism cells but they are not of a true geometric prism configuration. I don't know why they might be called prism cells or prismatic, or, if indeed it is even accurate nomenclature that I am using.

I soldered the cells together using the cell/battery manufacturer's very short pre-existing solder tabs. I made a new holder out of flat and angled pieces of plastic from the original surplus battery case, which previously held the cells.

I used a multi-purpose thick plastic paint to hold the plastic pieces together and to insulate electric connections as well as fasten the metal cells to my newly constructed plastic battery case.

I purchased about a 14 oz. container of the paint for around ten dollars at Home Depot. It comes in three colors: red, blue and black. I like the product and prefer the black color. I have used it most often to insulate wires where taping was impractical.

insula

snipped-for-privacy@webtv.net (C. Nick Kruzer) wrote in news:1824-4862E7F4-273 @storefull-3253.bay.webtv.net:

I never heard of that paint - sounds like a useful thing to have around, so that's a good tidbit to know ;)

- Kris

Yeah, It's handy. Although it is multi-purpose it is marketed as a "tool-dip". If you dip the bare metal handles of a pair of pliers, upon drying it gives the tool a nice, insulated, hand-grip surface.

When the paint almost ran out at the bottom of the container it became to thick to use. I think I thinned it with a combination of naphtha (lighter fluid), acetone and toluol. Very, very flammable! Be careful if you do this. Follow thinning instructions on label, I might have not followed instructions and improvised using materials I had on hand.

WARNING! Acetone is a polar liquid and can develop a static charge when pouring from one metal container into another metal container. A small static discharge can easily ignite acetone which burns like gasoline when ignited. To safely transfer acetone, securely connect the two metal containers together with wire before pouring. The metal handles are a good place to do this. Strong clamps or sturdy clips on the ends of the wire is smart.

Many tradegies have occurred when pouring acetone from one metal container into another.

To understand how static charges can develop from a polar liquid being poured, search terms: Lord Kelvin's Electrostatic Water Machine.

insula

Here is an interesting and simple experiment that demonstrates the generation of an electrostatic charge from the pouring of a polar liquid. If you are going to do this make sure to use water and not a flammable liquid.

insula