So following up on soldering and effects on cells, from this thread:
https://secondlifestorage.com/showthread.php?tid=9482
I wanted to observe & "over-do" soldering heat to see what might show physical signs of damage, so I destroyed a cell for science.
It was water damaged & self discharged to 0.7V but otherwise physically OK, not corroded or punctured.
The cell was a Samsung INR18650-30Q from a power tool pack. Purple jacket, white top ring.
Ambient temp here at time of test: approx 16degC
The soldering iron I used is this heavy dutyone, the tip is approx 45mm x 18mm solid copper & measured at approx 330 degC with a non-contact temp meter. I think it's 80 or 100W (label is toast sorry)
For the positive end terminal, I soldered to & held the iron on it forleast 15 secs.
The negative end was soldered to & held the iron on it for at least 20 secs.
(both timed with phone)
At the positive end I found this:
Note the connecting strip. IMHO, this strip would reduce heat conduction from the pos terminal pretty well.
The white seal edge partaround the CID/PTCterminal metal piece seemed to be very heat resistant (even tested with a gas torch, didn't soften, barely reacted)
Theblue insulator ring (sorry bit out of focus) also seemed to be completely undamaged. It was easily melted if touched directly with the iron (gas torch made it shrivel up immediately).
I cut the cell length ways like so:
Then soldered the neg end per above, then let is cool for ~ a minute then peeled it open & found this:
Basically no damage, maybe some softening of the blue disc but not significant, still intact, pic looks worse due to me peeling open roughly.
But what about the white layer? To see what happens I soldered more:
So I unrolled some of the cell & found the copper sheet. I soldered to that with light pressure on a still tightly rolled part & it collapsed inwards noticeably (obviously not good):
Unrolling a bit more to see the result:
Pretty badly destroyed separating layer ....
So the separating layer is not good with soldering heat & will be easily damaged.
Even though easily damaged, I didn't notice any damage or changes at the edges, eg from neg case
I unrolled more & checked the pos strip area, no visible damage at all.
So given the above and the connecting strip at the neg end is much shorter so I decided to heat that more by directly soldering to the internal strip to see if heat from external soldering would/could do any harm.
Before internal soldering(note white insulation layer is 100% intact after previous external soldering for 20 secs):
After soldering directly to tip of internal strip (note insulation melted back):
This is the first obvious damage I've observed so far. But is even this a problem?
There are extra layers if the white & kapton tape(high temp) there.
And I had to solder to the internal strip directly only a few mm from that. So I don't believe it is a problem.
My observations &summary:
- soldering for 20 secs with a large hot iron did no visible internal damage to either end of the cell
- at cell pos end, heat from soldering won't conduct to cell case much due to plastic seal.
- the pos end plasticseal seems tough & unlikely to be damaged.
- cell construction at pos end seems less likely to cause damage from soldering heat due to long connecting strip.
- the top & bottom (blue) insulator discs are susceptible to heat but seemed undamaged bysoldering.
- the internal separator layer is easily damaged by soldering.
- cell neg end is more likely to suffer damage than pos enddue to more direct contact of separator layer with cell casing
- soldering at the center of the neg end (not at edges) would be better (more likely to heat separator layer at edges of casing)
Caveats:
- I only tested on one cell
- other cells might be different
- there might be damage that's not visible, eg chemistry, subtle separator layer changes at neg end rolledge, etc
- air (from cutting cell open)might have influenced results (unlikely)
- my iron was ~330degC,hotter irons would increase damage probability
https://secondlifestorage.com/showthread.php?tid=9482
I wanted to observe & "over-do" soldering heat to see what might show physical signs of damage, so I destroyed a cell for science.
It was water damaged & self discharged to 0.7V but otherwise physically OK, not corroded or punctured.
The cell was a Samsung INR18650-30Q from a power tool pack. Purple jacket, white top ring.
Ambient temp here at time of test: approx 16degC
The soldering iron I used is this heavy dutyone, the tip is approx 45mm x 18mm solid copper & measured at approx 330 degC with a non-contact temp meter. I think it's 80 or 100W (label is toast sorry)
For the positive end terminal, I soldered to & held the iron on it forleast 15 secs.
The negative end was soldered to & held the iron on it for at least 20 secs.
(both timed with phone)
At the positive end I found this:
Note the connecting strip. IMHO, this strip would reduce heat conduction from the pos terminal pretty well.
The white seal edge partaround the CID/PTCterminal metal piece seemed to be very heat resistant (even tested with a gas torch, didn't soften, barely reacted)
Theblue insulator ring (sorry bit out of focus) also seemed to be completely undamaged. It was easily melted if touched directly with the iron (gas torch made it shrivel up immediately).
I cut the cell length ways like so:
Then soldered the neg end per above, then let is cool for ~ a minute then peeled it open & found this:
Basically no damage, maybe some softening of the blue disc but not significant, still intact, pic looks worse due to me peeling open roughly.
But what about the white layer? To see what happens I soldered more:
So I unrolled some of the cell & found the copper sheet. I soldered to that with light pressure on a still tightly rolled part & it collapsed inwards noticeably (obviously not good):
Unrolling a bit more to see the result:
Pretty badly destroyed separating layer ....
So the separating layer is not good with soldering heat & will be easily damaged.
Even though easily damaged, I didn't notice any damage or changes at the edges, eg from neg case
I unrolled more & checked the pos strip area, no visible damage at all.
So given the above and the connecting strip at the neg end is much shorter so I decided to heat that more by directly soldering to the internal strip to see if heat from external soldering would/could do any harm.
Before internal soldering(note white insulation layer is 100% intact after previous external soldering for 20 secs):
After soldering directly to tip of internal strip (note insulation melted back):
This is the first obvious damage I've observed so far. But is even this a problem?
There are extra layers if the white & kapton tape(high temp) there.
And I had to solder to the internal strip directly only a few mm from that. So I don't believe it is a problem.
My observations &summary:
- soldering for 20 secs with a large hot iron did no visible internal damage to either end of the cell
- at cell pos end, heat from soldering won't conduct to cell case much due to plastic seal.
- the pos end plasticseal seems tough & unlikely to be damaged.
- cell construction at pos end seems less likely to cause damage from soldering heat due to long connecting strip.
- the top & bottom (blue) insulator discs are susceptible to heat but seemed undamaged bysoldering.
- the internal separator layer is easily damaged by soldering.
- cell neg end is more likely to suffer damage than pos enddue to more direct contact of separator layer with cell casing
- soldering at the center of the neg end (not at edges) would be better (more likely to heat separator layer at edges of casing)
Caveats:
- I only tested on one cell
- other cells might be different
- there might be damage that's not visible, eg chemistry, subtle separator layer changes at neg end rolledge, etc
- air (from cutting cell open)might have influenced results (unlikely)
- my iron was ~330degC,hotter irons would increase damage probability