Soldering battery packs

[Elliott Hopkins]

I'm trying to knock up three 6x1 sets for Newbury on Sunday. But I'm making a real fist of it (it's my first time). I've whacked the soldering iron up to full power, but I'm paranoid I'm going to cook one of the new cells.

I need to apply an impulse of heat instead of slowly heating the cell up don't I? The bars at the positive terminals go on fine, but the bigger -ve terminals are a real asspain.

Can anyone direct me to a good tutorial on battery pack construction?

Thankyou.

Elliott.

[jimmy]

What sort of iron are you using ? wattage is wholly unimportant, its size that counts With my iron, I have to do one cell at a time then give it 30 seconds or so to warm up again - then it is fine.

Scratch up the surfaces you want to tin first, maybe use some flux on there too.

[DCM]

lightly sanding the +ve and -ve of the cell, get a little soldering flux (plumbers flux will do if desperate), use a tip that is rather beefy, allow the iron to warm up, place bar on cell, clamp, apply heat, when you hear the flux sound like frying baking, apply solder.

If you don't have a big fat tip, get someone to do it for you. I would offer, but it is a tad far for you to come for me to solder them up.

[Spencer Mulcahy]

Make sure that your iron tip is clean sand or file the end defore each cell I have found this helpful when soldering V2 motors hope this helps.

[neiloliver]

I pre-tin the back of the battery bar that will be in contact with the cell and then apply flux to the cell positive or negative of the cell. I then drop the bar onto the cell and heat the bar from the top so it re-flows the solder underneath and solders to the cell surface. I also 'inject' some solder at 45 degrees whilst i am doing this.

I big hot iron is the trick. Cells HATE being soldered like this and i have to hit my head against the wall each time i do it because we WELD millions per year at work and i have written technical manuals saying NEVER SOLDER TO CELLS. The problem is that the heat does three nasty things:

(1) when soldering the negative, it can melt the seperator material between the anode and cathode
(2) when soldering the positive, it can effect the properties of the rubber slug that forms part of the vent mechanism which can lead to the cell not venting at the correct pressure
(3) also on the positive, it can melt the insulation ring that sits around the top cover and keeps the positive button insulated from the negative can.

but if you want to win races you have to entertain the devil... (or something like that)....

Seriously, a copper, braid welded joint between two cells would be just as good as some fancy gold plated battery bar.. but none of us have £10,000 cap discharge, water cooled cell welders in our homes so we are stuck with soldering....

N

[Elliott Hopkins]

It's an average sized pen tip type iron, but I'm getting it up to 420°C. It's got a variable temperature dial. It's a cool piece of kit. It's work's.

I'll try an iron with a larger tip. Dad has one.

Thankyou for your advice. I do want someone to do it for me. I'll have to ask Dad.

Elliott.