Soldering on 18650, no ill effects. Results here...

Overclocker

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about 10 months ago i soldered together twelve 8P packs (samsung 26F cells). as shown above the soldering was done very quickly to minimize damage.

i set aside 8pcs of the samsungs that i DID NOT SOLDER TOGETHER

now after about 2000kms on the 12s8p pack i decided to see how much deterioration occured COMPARED TO THE UNUSED UNSOLDERED CELLS. so i hacked together a simple 8P holder (spring contact for negative side) for the UNSOLDERED CELLS, shown here:

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i charged both soldered and unsoldered cells on the icharger 106b+. 4.17v end voltage. discharged to 3.10v at a low 4.0A (to minimize effects of contact resistance on the unsoldered cells).

RESULTS:
SOLDERED: 19,910mAh
UNSOLDERED BRAND-NEW CELLS: 20,278mAh

NOTES:
the SOLDERED cells had about 2000 kms on them, probably 25 cycles? LVC was set to about 3.30v per cell. mostly charged to 4.10v. just a couple of times to 4.20v.

CONCLUSIONS:
1) the tiny difference could probably to attributed to normal li-ion wear.
2) soldering using my process doesn't seem to harm cells
 
You are posting this as if you followed the scientific method and state a conclusion, yet you have a pretty large uncontrolled variable that renders your results entirely inconclusive. They definitely have less capacity as measured in your tests, but you are unable to say if that is due to normal use or the soldering... it is wishful thinking at this point.

If you really wanted to try to prove the point do the experiment again, but put the same number of cycles/load on both sets of batteries and then we will have something to discuss.
 
ecycler said:
You are posting this as if you followed the scientific method and state a conclusion, yet you have a pretty large uncontrolled variable that renders your results entirely inconclusive. They definitely have less capacity as measured in your tests, but you are unable to say if that is due to normal use or the soldering... it is wishful thinking at this point.

If you really wanted to try to prove the point do the experiment again, but put the same number of cycles/load on both sets of batteries and then we will have something to discuss.
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yep i'll be doing that coz i now want to build a 13s8p pack. so i need to "wear" the unsoldered cells to make them match the used cells. but this could take a while...

if you read closely i did use the words "probably" and "seem" in the conclusions part. i went ahead and posted this now because i was expecting a much bigger difference! the fac that there's such a small difference already says something
 
True, it cant be poinpointed where does come from de 2% loss capacity.

But worst case scenario is that all this 2% loss come from the soldering, not from cycles, not from measurement error, not from cell tolerance or anything else.

Not too bad for me.

Regards
 
I believe, and most everyone fears, that soldering an 18650 cell might result in some major or catastrophic damage or failure.
It seems reasonable that a 2% degradation after many cycles to be attributable solely to cycle wear.

But ...
More and differing test are always appreciated!
 
DrkAngel said:
I believe, and most everyone fears, that soldering an 18650 cell might result in some major or catastrophic damage or failure.
It seems reasonable that a 2% degradation after many cycles to be attributable solely to cycle wear.

But ...
More and differing test are always appreciated!
Click to expand...

The catastrophic damage I have encountered has been from too much heat applied and the insulation melting, thus resulting in the nickel strip above shorting to the bare case of the battery. This happened to me on 2 batteries when building a monster pack with Dr. Bass' konion makita packs - until I learned. My soldered konions seem to be holding up very well and I don't think much capacity was lost either, but I am all for scientific 'data' and proper method to better understand what the actual capacity loss may be over time from heating the terminals to those high temps. I do want to say that the measured 2% would be an acceptable loss, but my issue was with the misleading thread title given the huge unknown variable and the statement of 'no ill effects' when that can't be quantified.

There are people who say you should not even weld to the very center of the battery terminals, so they make circles around the edges.
 
You're using Samsung ICR18650-26F cells, yes?

Data sheet for such is here:

http://www.all-battery.com/datasheet/30612_datasheet.pdf This is for the Samsung ICR18650-28A, but it's a very similar battery.

I quote:

6.1 Connection between the cell and the battery
6.1.1 The cell should not be soldered directly with leads. Namely, the cell
should be welded with leads on its terminal and then be soldered with
wire or leads to soldered lead.
6.1.2 Otherwise, it may cause damage of component, such as separator and
insulator, by heat generation.
Click to expand...

25 cycles should not cause a significant capacity loss. Nor did you test the cells immediately after soldering to see what happened.

I'm good with listening to the manufacturer of the cells who says, "Don't solder directly on these."

A spot welded tab is slightly warm to the touch immediately after welding. I suspect, even if you were fast, you wouldn't be willing to touch the connection immediately after soldering.
 
ecycler said:
but my issue was with the misleading thread title given the huge unknown variable and the statement of 'no ill effects' when that can't be quantified.
Click to expand...

not interested in splitting hairs. nor in finding to 20 decimal places the "effects" of soldering. it's a cheap ebike not a space probe.

you're free to do your own lab tests if 1.8% isn't good enough for you :roll: most people just want to see if soldering harms the cell in a big way

http://jes.ecsdl.org/content/162/8/A1592.full
u3QNAkj.jpg


shows capacity loss in the same ballpark after 25 cycles

anyway i'm now cycling the unsoldered cells in the icharger (good thing it could be automated)
 
Syonyk said:
You're using Samsung ICR18650-26F cells, yes?

Data sheet for such is here:

http://www.all-battery.com/datasheet/30612_datasheet.pdf This is for the Samsung ICR18650-28A, but it's a very similar battery.

I quote:

6.1 Connection between the cell and the battery
6.1.1 The cell should not be soldered directly with leads. Namely, the cell
should be welded with leads on its terminal and then be soldered with
wire or leads to soldered lead.
6.1.2 Otherwise, it may cause damage of component, such as separator and
insulator, by heat generation.
Click to expand...

25 cycles should not cause a significant capacity loss. Nor did you test the cells immediately after soldering to see what happened.

I'm good with listening to the manufacturer of the cells who says, "Don't solder directly on these."

A spot welded tab is slightly warm to the touch immediately after welding. I suspect, even if you were fast, you wouldn't be willing to touch the connection immediately after soldering.
Click to expand...

cool to the touch after 2 seconds. it tried touching :D

that said i'll still be ordering the JP Welder soon
 
Well, if nothing else, you certainly proved that you can solder well. Great skill to have, but in the big assembly factories they obviously can't afford to take the chance employees won't be as good. So for sure, tab spot welding is much easier to quality control.
 
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