soldering practice or insanity

[fletch51]

I just finished. It only took a week. Just needs heatshrink covering.

These were two 10S 5000mAh packs and two 8S 3800mAh packs. All brand new.

Now there are ten 2S 5000mAh packs and eight 2S 3800mAh packs, and a pile of Deans connectors.

They could have been sweet FE packs, but now RC car.

sanity or sacrilege?

 

[properchopper]

Nice work ! How 'bout a brief tutorial on how you did it ? Soldering tabs on lipos has always been tough for me & would be good information to have on what materials you used, prep & such.

Thanks,

Tony

SoCal FE

 

[fletch51]

I simply did a lot of normal soldering with a normal 40 watt soldering iron.

I imagine you are talking about the positive terminals, which are aluminum(or some metal that solder doesn't adhere to).

These lipos, and I Imagine all Lipos, have a piece of nickel plated tin spot welded on the positive terminal.

So when seperating the cells, as long as you cut the terminals in such a way that leaves the tin on the positive terminal, you can solder straight to them.

Care must be taken when moving the terminals around, because they can break off like a pull tab on a coke can if you move them back and forth too many times. I had this happen on one cell and I started looking up what tools/materials to re-weld or solder it back. Then I just realized I can use a tiny screw and nut, so I drilled small hole thru the tin and aluminum, and mechanically fastened them. When running this one I will have to check to see if that terminal gets warm or hot, but in the little 1/10 scale cars, current draw is not crazy high like in boats.

Most of the work was soldering wires to the deans(making "pigtails") and sepearting the packs, they have super thin double sided tape between all the cells.

I used a putty knife(metal one because they are thin) and lacquer thinner dispensed out of a syringe with a small straw(from super glue section at hobby shop) epoxied to the end.

When seperating packs go slowly. First apply some lacquer thinner to the seam of the cells to be seperated, then very gently push the putty knife between the cells only a little way, then squirt some more laquer into seam, and push putty knife a little more, repeat a few times and eventually, you can start pulling packs apart by hand, adding lacquer as you go.

You have to be very gentle pushing the putty knife between them because it marks up the packs worse and worse with more pressure(and could puncture the pack).

You must let the lacquer do most of the work when pulling apart because the foil sleeve can pull away from the cell. which a little is ok, it just isn't as pretty when you press it back. It will leave wrinkles.

There will be a lot of nasty sticky adhesive left behind from the double sided tape, lacquer thinner on a paper towels cleans it up nicely.

 

[properchopper]

Thanks for taking the time to explain this. I've run into the situation on some lipos where the plated tin tabs were just crimped onto the aluminum and didn't make good contact. I bought some aluminum-specific solder and flux & did the best I could; worked OK but sure wasn't pretty.

 

[fletch51]

Yeah, I agree, I dont know how well the crimped spot weld conducts(It should be an electro weld of some sort even if it is folded over and crimped, during the crimp is when the electric is applied to weld them together).

I signed up at offshoreelectrics only days ago, and I've read some of your posts there , they are very informative. I'm glad to hear that the aluminum solder I've read about does work, even if only to a degree.