Wrong solder or just bad soldering technique?

Prahe86

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Joined
Jan 18, 2017
Messages
34
Hi,

I am a novice at soldering.

I notice what i assume is excess flux around the areas where i have soldered the batteries and the bus bar.

Please take a look at the attached photos and let me know if you think:
1) I'm using the wrong solder (i'm not using any flux other than what is included in the solder);
2) my technique is poor; or
3) everything is okay.

thanks,
Paul



image_qqanni.jpg

image_xnqgdo.jpg

image_ygdxzb.jpg

image_mqihyw.jpg
 
You need to have the part you are soldering hot enough to melt the solder. Try practicing on a piece of your metal tape and use as little solder as possible. Every one will tell you to try and do as little heating to the battery as possible hence some people will use a small soldering iron. When I solder to battery cells I use a 100 watt pistol style soldering iron made by Weller. When it is good and hot i can make my joint in about one or two seconds. Just practice practice practice and good luck.
 
Yes, for the cells you need more heat, definitely. You can use a 30/40 watt iron, but you need to put a larger tip on it. You need heat mass when soldering. I actually made my own from some copper wire (not sure of the size off the top of my head). It works rather well for the cheapo soldering iron it's connected to.

Others will use the 100 Watt, and I think there are some who are using 150+ watt irons.

Flux is fairly easy to get off. I don't remember the chemical you can use to wipe it down. However, you could probably use a copper wire brush to gently brush off the excess. Copper wire brushes won't scratch or rip the solder join apart.

For flux, I do have some rosin core solder, however, I also use the paste as well. I feel that you can almost not have enough flux as it burns away usually, and what's left behind can be cleaned up.

Another thing you can try, and some will say nay on this, but you could put the solder on the tip of the solder gun. I do that for most of my connections (but I have a slight pocket in my tip that holds it since it's custom built). Then when you touch the tip to your work, as soon as the work is hot enough, the flux runs in to fill the space up, and my joints look really smooth.

Please note, I have not done any cell soldering myself yet. Most of my soldering is just wires to boards and to other wires. But I'm sure the technique is pretty similar.
 
I've found 63/37 leaded solder is easiest to work with on cells, just make sure you have proper ventilation. If needed, make sure to only use electronics flux and nothing plumbing related. Excess electronics flux does not need to be cleaned.
 
Looks like to little heat mass. Big tip is recomended. Watt is good to have but 50+ is enough if the tip mass is massive. I use an 150+w iron with giant mass tip. i just barely touch the cells and its done. The mass is the thing here!
 
Prahe86 said:
Hi,

I am a novice at soldering.

I notice what i assume is excess flux around the areas where i have soldered the batteries and the bus bar.

Please take a look at the attached photos and let me know if you think:
1) I'm using the wrong solder (i'm not using any flux other than what is included in the solder);
2) my technique is poor; or
3) everything is okay.

thanks,
Paul



image_qqanni.jpg

image_xnqgdo.jpg

image_ygdxzb.jpg

image_mqihyw.jpg

Thanks to everyone for the replies.

I'm using a Weller 100 watt soldering iron, but I'm using a small soldering iron tip.

I'll try using a larger tip for the soldering iron and see if that helps.

Thanks again,
Paul
 
Yes, Use the largest one included you can. That will do ALOT :)
 
Another thing you can do is add thermal mass to your tip. You can have small tip that touches the soldering joint, but above that you need a lot more mass; not just a thin straw shape. You'll notice in some of the other threads some users have a solder tip that it huge (compared to the iron) and slightly curves and tapers down to a more manageable point.
Just for testing purposes, you could take some copper wire and wrap around the tip tightly to add some thermal mass and see how that works for you. Then you'll know you need a larger tip, a bigger iron, better solder, more/less flux, or better skills ;)
 
Oh, if you have the exact same iron, then you shouldn't be having any problems at all. Something doesn't sound right. Is the tip oxidized? I stick mine in the bench grinder with a wire brush every so often to clean off oxidation. Also, the tips screw on. Use a pair of pliers to make sure it's nice and tight. If it's not fully tight, heat won't transfer right.
 
Thanks Mike, I am going to return the POS soldering iron I bought on Amazon and get this one. I think I fell for the look of the X-TRONIC 3000 but when I used it, man what a POS. I just had to spend way too much time on a cell.
 
Hi Guys.

i've been using a weller 100 watt iron with a large soldering iron tip, but, as far as i can tell, i'm still having issues with excess flux.

if you have a few minutes, would you please take a quick look at the attached video?

if i can't stop having extra flux, is there a way to remove it safely?

I'm only concerned if the flux will eventually eat into the battery cells. if the cells are fine and the flux won't damage them, then i'm fine with the extra flux.

 
I brush all my cells afterwards to get rid of the excess flux:

I hav it in one of my videos of youtube and was going to link it in but dont find it. I use a normal wirebrush and it works great.
 
daromer said:
I brush all my cells afterwards to get rid of the excess flux:

I hav it in one of my videos of youtube and was going to link it in but dont find it. I use a normal wirebrush and it works great.
Do you include something like rubbing alcohol?
 
No i dont. I wouldnt do that on the positive side atleast. on negative it should be fine.

By just brushing it most of the excess is removed. If its enough im not sure though. But its better than from start.
 
Question.... Is soldering just as good as spot welding? I need to build my first battery pack and was not sure which way to go.
 
I would say yes. So as long as the solder joint is done correctly. The biggest difference electrically would be that solder has full contact between cell material and wire; whereas the spot welding only really has 4 solid connections.

There isn't really anything wrong with either method. Either one will work equally as well, and last just as long as the other; so as long as they are done correctly.
 
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