Soldering battery packs
 

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.

What sort of iron are you using ? wattage is wholly unimportant, its size that counts :p 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.

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.

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.:D

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

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.

Make sure you tins the battery surface b4 you solder. What temp is your iron set at. My iron takes about 10 seconds to heat up.

Buy a deans battery jig there not exspensive but i have one and they make building cells so much easier. I find the easies way is to sand the + and - of the cell a touch then use multicore solder and hold your iron over the terminal not touching and just put loads of solder on the tip until it drops onto the terminal then just hold the bar on and put the iron on top and wait give it a few seconds to push its self down on to the cell.

A

Ashley, the reason why you do it that way is that if you touch your iron onto the cell, it saps all the heat away.

To efficiently and safely solder cells, you need

1. Decent solder
2. Flux
3. The correct tip, with a large mass, not a small tip.

oh...

and patience!!!

http://www.rccaraction.com/articles/build_battery.asp
This is pretty good. Although i would just sand the ends, you can use a dremel sanding wheel LIGHTLY.

Although if you are not confident, i would pay someone to do it, no point in risking damaging them for the sake of a few quid.

Do not use the hair dryer if you arn't heatshrinking ;)

The guide hasn't got the best soldering in the world ive just noticed, i hope your better :D

And also you want to keep the cell as cool as possible as you should have the iron on the cell for a short time as possible to reduce risk of damage.

Also i dont think you need flux i have alwaysused multicore solder and i have never had a pack of cells fall apart on my and never had a bad connection. But if your used to using flux use it. And a big tipped soldering iron is essencial thats why i got my big iron it gets so hot you can feel it just sitting buy it.

A

heres a question, why - no matter where you position your head when soldering, does the flux smoke go straight up your nose ?:o

Keep chasing that dragon Jimmy.:D

The best tip I've had from you guys (not saying the others aren't good), is the buffing of the end caps with a scouring pad. The solder adheres so much better even with the diddy tip.

I've almost done one pack sneakily at work. It looks cack.

I might get a metal jig made to dissipate heat from the core of the cells. Yup not using one at the minute.

I doff my cap to you guys. Thankyou.

Elliott.

Sometimes its the soldering iron wattage, the smaller irons just dont have it for batterys and some motor connections. Its worth looking at the 12volt irons used at meetings, these have nice big ends, stay hot when put to the battery, I am sure if you look around at CML racetrack meeting you will get lots of help.

Dude, why don't you listen to people with far more experience than you at soldering in general and building battery packs in general. The flux allows the solder to flow more freely, adhere better to the surface, and also helps reduce oxidisation.

yes you can solder cells without flux, but it is far better to use it, if it wasn't, I wouldn't recomend it

Thats what the "multicore" is, the flux is the core in the solder !,

First pack I made, held the cells in a metal vice......almost diddent need a soldering iron, the cells got hot while they shorted !! "I might get a metal jig made to dissipate heat from the core of the cells"

(watch out for plumbers flux, this can be quite aggressive, enables plumbers to solder copper joints without cleaning the copper)

yup multicore solder has flux in the middle its just when your soldering you never have enought hands so i find it easier as you only have to hold the solder instead of fiddling with the little tub of flux and the solder and pliers and everthing else.

A

WTF.... multicore solder is designed for general soldering, like tinning wires etc, the flux is there to help the solder flow a little better, when you solder cells, the multicore solder doesn't flow fast enough, thats where a pot of flux comes in.

Ashley, you use a little brush, or anything, take a dab out, and rub it on where you want the solder to go, then you got two option.

If your iron isn't meaty, tin the battery bar, place it on the cell then apply the iron with a tinned tip (it transfers the heat better) and just slide in a little solder.

If you got a meaty iron, place the battery bar on, tin the tip of the iron, then apply heat and solder, done, takes two seconds.

If you would only ask questions rather than typing without thinking, you would get these answers.

Oh Ok soz DCM

Its just i have never used flux and didnt fancy the hastel of learning and multi core did the job maybe i should use flux on my next pack ill give it ago. Thanks DCM

And i have a big beaffy iron 80 watt giant tip hehe beast.

A