Soldering directly to batteries

Maschinen Krueger · Post by **Maschinen Krueger** » Mon Dec 07, 2009 1:36 pm

I want to make a custom 3V battery pack using two 357 coin cells and a 2.5mm/5mm DC plug. Think of the pack as a plug in fuel pod.

Can I solder the wires directly to the +/- with out damage to the cells? I know you can tack weld metal strips to cells, but what about the sustained heat of soldering? Or would 5min epoxy work better?

Thanks in advance.

Just getting into this LED stuff for models.

Kylwell · Post by **Kylwell** » Mon Dec 07, 2009 3:17 pm

I've done it in the past w/o an issue. I'd guess to minimize the heat as much as possible. Did it with 12v RC car batteries.

en'til Zog · Post by **en'til Zog** » Mon Dec 07, 2009 4:17 pm

I wouldn't. Soldering to a battery pack usually means soldering to tabs sticking out of the pack, not to the cells IN the pack.

Why not just use a 3 volt coin cell, and a coin cell holder? Or a 3.6 volt cell to better match most BLUE and WHITE LEDs?

Chacal · Post by **Chacal** » Mon Dec 07, 2009 5:02 pm

Batteries (and cells) are usually difficult to solder—the solder doesn't 'stick' properly (that's why the 'tabs' are usually spot-welded to the battery/cell).

I would use large-diameter heat shrink tubing to hold the two cells and the wires together, then I'd 'lock them in' with epoxy putty.

tetsujin · Post by **tetsujin** » Mon Dec 07, 2009 5:31 pm

en'til Zog wrote:I wouldn't. Soldering to a battery pack usually means soldering to tabs sticking out of the pack, not to the cells IN the pack.

Why not just use a 3 Volt coin cell, and a coin cell holder?

I don't know if my space requirements are typical of most - but I haven't seen a lot of good off-the-rack solutions for a small, good-capacity power cell and a matching battery holder... For instance, I have some CR1220 battery holders - but a CR1220 doesn't store a lot of power (it's a thin battery) and the battery holder adds so much bulk that the advantages of the CR1220 are mostly lost. The battery itself is 12mm wide and 2mm thick, but add a battery holder and it goes up to 15mm wide and 5mm thick...

The smallest coin cell holders I've seen are those made to be mounted to a circuit board - but a circuit board would itself be about 1.5mm thick (for the ones I can readily buy or make, I mean) - so that also doesn't really get me anywhere...

It's basically gotten to the point where I rarely plan to have my power source inside the model any more. It just doesn't seem to be worth it.

Kylwell · Post by **Kylwell** » Mon Dec 07, 2009 5:48 pm

Oh, and BK, if you need it I've got a AAA 3 cell battery holder if you need it.

Maschinen Krueger · Post by **Maschinen Krueger** » Mon Dec 07, 2009 6:13 pm

Thanks guys. I'll be experimenting.

macfrank · Post by **macfrank** » Mon Dec 07, 2009 6:51 pm

Chacal wrote: I would use large-diameter heat shrink tubing to hold the two cells and the wires together, then I'd 'lock them in' with epoxy putty.

I've done it, and it works well. (just a dab of epoxy in the heat shrink "pucker" where the wires come out and another dab on the other end - I had both wires coming out of the same hole.

Just make sure that it's easy to remove the "power cell" from your model once the batteries die.