Need Help on Soldering Lipo Cells

A

airflow

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Jul 21, 2018
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Hi

I need some help on soldering some 21700 cells. I'm creating a 10S3P pack. I got the negative side all soldered up. All the connections look good and are strong. But I can't get the positive side to work. The solder just won't stick. I'm using Kester 186 flux, American Solder 60/40 rosin core. I tired setting the 60w soldering iron at 300C, 400C, and even 480C. I tried tinning the batteries first but the solder just balls up. I tried with flux and without flux also.

Any suggestion / help is appreciated. Thank you.


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take some sandpaper and lightly sand the terminals. This will remove a layer of dirt on the cells to make the underlying metal be accepting of the solder. Just make sure you cover all of the scuffed area as any that's visible will be exposed to oxidation if you get through the nickel coating.
 
Korishan said:
take some sandpaper and lightly sand the terminals. This will remove a layer of dirt on the cells to make the underlying metal be accepting of the solder. Just make sure you cover all of the scuffed area as any that's visible will be exposed to oxidation if you get through the nickel coating.
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Thank you for suggestion, I dont have any sand paper so I used some steel wool, I also tried scratching lightly with a screwdriver. It didnt help.

The balls of solder scratch off with any force.
 
1. Try to clean them with vodka

2. Try a liquid flux. It's also called "soldering acid" or ???????? ??????? in Russian. I'm using this one:

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not2bme said:
Not hot enough. Try a 150W. Also try another solder, especially if it's some chinese brand.
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Thanks. I'll give it a try. any solder you recommend?


thunderheart said:
1. Try to clean them with vodka

2. Try a liquid flux. It's also called "soldering acid" or ???????? ??????? in Russian. I'm using this one:
Click to expand...

Thanks.I'm using the Kester 186 liquid flux.
 
BlueSwordM said:
https://www.amazon.com/Weller-SPG80...ller+80w&qid=1532212358&sr=8-2&ref=mp_s_a_1_2

I have it, and it is an absolute monster of an iron. It's HUGE, has a lot of thermal mass, and can solder cells in 2 seconds.
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I have that one as well. I got it for $5 at a garage sale ;) It takes awhile to get up to temps, but once it's warmed up, it's like a diesel engine and just keep on chugging w/o issues.
Only issue is that it's tip heavy, so it fatigues my hand after about 10mins of using it. I've been considering putting a counter balance. Plus a better heat-shield.
 
You're one lucky guy.

I bought it for 35$CA when it was on a sale. It's not as massive as the one that Daromer has, but it still is excellent. 9/10 for a big soldering iron.

The only thing I would like to do is put a PWM controller on the end of AC plug to the iron. That would be so helpful.

The problem is that it gets extremely hot, which is good, but as it has no heat control and a lot of mass, it heats up a ton, and that means oxidation is a big problem. Toning down power using at least PWM to say, 90% duty cycle when it is hot, would help tremendously.

Also, as all extremely hot irons, it sucks up a lot of solder.
 
Yeah, I had to do a lot work on the tip to remove the oxidation from the previous owner. It also didn't help that the iron sat out in his garage (Fl weather with high humidity) for a few years without use. There still needs to be some more work to it, but I want to either look into new tips, or possibly replate this one.

A PWM control would be nice. Might even be able to wire up a thermistor, transistor, varistor to help out.


But, back to the OP. Definitely recommend a bigger iron ;)
 
So there are several you tube videos about brazing the aluminum tabs with aluminum wire sticks

Has anyone given this a try as an alternative to expensive flux that allows aluminum tab to bond to solder

Tks
 
Chablis_m said:
So there are several you tube videos about brazing the aluminum tabs with aluminum wire sticks

Has anyone given this a try as an alternative to expensive flux that allows aluminum tab to bond to solder

Tks
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Soldering aluminium is not recommended. It is really difficult. I would suggest spot welding. Aluminium oxidizes very very quickly, which means that you have to solder it very soon after you clean it. You will require acidic flux, which can cause corrosion if not completely removed.
 
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