Self-Discharge UPDATE On 30Q 141 Cells

[eMark]

no to 30Q fixing itself

One question (with respect to 30Q) is: What is acceptable mild discharge? Maybe, he meant was self-discharge higher than normal, but not as high as a certain percentage of cells in a 30Q battery pack. Do you generally agree with BlueSeas previous post pasted below (i do) ...

The observed phenomenon of high self discharge may be true for many cells, and further may go largely unreported. Especially if the charge process has an effective balancing routine to rebalance the pack.

This is especially true with the interconnecting of parallel and series bus bars giving a false impression that the individual cells in the p-groups are closer in voltage and mAh than the individual cells' actual resting voltage (when taken alone instead of linked together in a p-group).

This self discharge isn't by itself in most cases isn't a reason to trash the pack...or even the cell. But does require some degree of balancing.

That is generally true (e.g. MJ1/M36 cells), but not so true with 30Q being the one Li-ion cell most often reported as prone to "high" self-discharge. High enough so as to diminish a packs' effectiveness and the potential of an internal short in one of the p-groups. This is why i decided from the GetGo with my VRUZEND 10S3P to bottom balance the p-groups within a few mV of each other before straight charging the two sub-pack 5S3P paralleled p-groups within 10-15mV of each other using two 5S3P paralleled sub packs for bottom balancing with 2S-6S balance charger before straight charging.

if 1 cell is bad in a p-group it will take out the entire p-group, even the good cells.

Because of the interconnected series and parallel bus bars it's difficult to know which p-group has a "bad" cell(s) with a not-so-smart BMS ... until the BMS finally cuts off power due to cell(s) failure. That might be one definition of a "bad" cell when the BMS cuts off power due to cell failure and not moderate self-discharge even though it's greater than what's considered normal self-discharge for a particular Li-ion cell chemistry or energy density.

Whereas as BlueSeas points out a cell with moderate self-discharge that's higher than normal for that cells' unique chemistry may still serve a useful pack purpose for many charge/discharge cycles until it finally poops out (fails), and the BMS shuts down the battery. A percentage of 30Q cells are apparently more problematic (high self-discharge) than are MJ1/M36 cells (5 to 10Ah) or another brand name high energy cell (15 to 20Ah).

when you built the 2s5p i thought it wouldve been a good test to see if doing the 0.6amp discharge/charge 4.2v/2.5v would be able to save a pack without disassembling it and replacing cells but you stopped early on the charge without completing the process because of length of time it was taking by having the 3.44v cell paralleled in the group it will be brought down by the self discharging cells

That 12hr "balancing charge" showed that it was NOT the 3.44V cell (that one would think) that was the reason for a lengthy "balancing charge" (although it contributed), and still only a 2S pack voltage of 7.48V (3.74V per each 1S5P groupafter 12 hrs). That's only an increase of 1.16V using balance charging at 0.60 amps (.2C) for twelve hours. That justifies my reason for not using a BMS ... ineffective when it comes to top balancing the p-groups. It was the 2S3P 3.53V cell that failed before the 3.44V cell and reason why cells with high self-discharge dramatically slow down balance charging the lower the charge amperage (e.g. 0.60 amps) ...

1S1P 2S1P
3.56 3.44
1S2P 2S2P
3.70 3.73
1S3P 2S3P
3.53 3.53 (damaged cell when pack was drained for only 2.58V bounce back after 24 hrs.
1S4P 2S4P
3.65 3.62
1S5P 2S5P
3.70 3.70

This failure of the 2S3P cell did not result in an internal short but was significant enough being the primary cause of the extended 12 hrs for the 2S5P pack voltage to go from 2.58V to only 3.74V. An increase on only 1.16V over 12 hrs because of resistance discharging around 0.40 amps.

why did you switch from 5s2p to 2s5p

Isn't it generally assumed that the more cells in a p-group they tend to keep each other balanced with less stress on each individual cell in a p-group? If i would've built a 10S5P 30Q 141 VRUZEND battery pack it's my understanding that instead of nine cells showing higher than normal self-discharge (3.44V-3.70V) of the other 20 cells (3.75V-3.74V) and one other cell at 3.73V after five days.

your hobby charger would be able to do the test in less than half the time at 5s2p

Didn't use a HobbyKing charger. It's very similar to the iMAX B6 with ability to check p-groups' IR. It's like the B6 circuitry so you need to take at least 3 p-group readings as each one can vary by 2-4mΩ, then average them out or take the three lowest readings as suggested by another member (think it was Serious Sam).

Am running 4-5 more tests that i started yesterday evening. The purpose is to confirm at least in my mind that just because a 30Q cell leaks mAh doesn't mean it looses it's ability hold the same capacity as one of the other "good" twenty cells in the 10S3P 30Q 141 VRUZEND battery having the same number of charge/discharge cycles as the ten other cells showing higher self-discharge (3.73V to 3.44V from 1/5/21 to 1/15/21. The "good" twenty cells had the same cell voltage on 2/12/21 as on 1/5/21.

Will post the results of the capacity holding ability of 4-5 different 30Q cells on Monday ranging from a new 30Q "6 KH1T" cell with only a couple moderate charge/discharge cycles to the 3.44V cell having the highest self-discharge with 170 charge/discharge cycles in 2020. Each test will be discharged to 2.5V, then 1 hr rest before charging to FULL (4.2V). Each charging at 1.5 amps for 2:45 hrs which is usually when the final charge has dropped to 0.05 amps just before the MiBOXER flashes FULL. It's possible that using a new 30Q cell or an unused 30Q cell in storage for 14 months it may not take 2:45 hrs to reach FULL. Will post results Monday afternoon.

 

[goatman]

goatman wrote: ↑Feb 11 2021 8:24pm
when you built the 2s5p i thought it wouldve been a good test to see if doing the 0.6amp discharge/charge 4.2v/2.5v would be able to save a pack without disassembling it and replacing cells but you stopped early on the charge without completing the process because of length of time it was taking by having the 3.44v cell paralleled in the group it will be brought down by the self discharging cells
That 12hr "balancing charge" showed that it was NOT the 3.44V cell (that one would think) was the reason for a 12hr "balancing charge" and still nowhere close to a 2S pack voltage of 8.4V (4.2V per each 1S5P grouping). It was the 2S3P 3.53V cell that failed before the 3.44V cell ...

yes i typed wrong, wasnt clear
if the 3.44v cell is now the "good one" it will be brought down by the bad cells in its p-group

when doing a test its usually easier and more accurate to do 1 cell at a time than a bunch all at once

goatman wrote: ↑Feb 11 2021 8:24pm
why did you switch from 5s2p to 2s5p
Isn't it generally assumed that the more cells in a p-group they tend to keep each other balanced with less stress on each individual cell in a p-group? If i would've built a 10S5P 30Q 141 VRUZEND battery pack it's my understanding that instead of nine cells showing higher than normal self-discharge (3.44V-3.70V) of the other 20 cells (3.75V-3.74V) and one other cell at 3.73V after five days.

they will settle to the same voltage as the weakest cell in the p-group, whether its 2p or 10p
the difference would be the amps going into the bad cell

dead short on 5p of 30Q could be 200amps? 400amps?
but dead short on 2p might be 40amps? 80amps?

youre dealing with a slight self discharge

id put the 3.44v cell off to the side, all by itself and see if the self discharge has stopped
if it has, do the other self discharging cells and see if it works on them.

 

[eMark]

yes i typed wrong, wasnt clear

me too so am reposting a couple paragraphs that need further clear-if-cation :wink:

I spent nearly 30 minutes making several edits after posting the above lengthy post. So, for those that may have opened it soon after my post and likely confused ... my apology. Even after i thought all was clear after i got home and read again i saw it was in need of further clarification. As my wife said before we were married "I'm not beautiful but i try" but to me she's beautiful. So too i try diligently, but never seems to be quite good enuf. To err is human (30Q QC) and maybe 30Q's problem is too expensive to "fix" by Samsung ?

if the 3.44v cell is now the "good one" it will be brought down by the bad cells in its p-group

The 3.44v cell will (IMO) NEVER be good. Like you i too hoped a "fix" or at least a lessening the "high" self-discharge was possible. None of those cells (well maybe the 3.73V) will be reassembled again into the 10S3P, but disposed of before March madness.

when doing a test its usually easier and more accurate to do 1 cell at a time than a bunch all at once

Yes, and that is what i have also been doing besides the 5S2P & 2S5P experimental testing.

they will settle to the same voltage as the weakest cell in the p-group, whether its 2p or 10p ... the difference would be the amps going into the bad cell

True, but it's my understanding that you can prolong the eventual higher discharge than normal with more p-groups as there is less stress on each cell in a 10 p-group than a 5 p-group.

id put the 3.44v cell off to the side, all by itself and see if the self discharge has stopped ... if it has, do the other self discharging cells and see if it works on them.

From my numerous on-going tests since 2/16 (not all have been posted) of those ten cells i will be putting 7 out-of-site and out-of-mind if you follow my drift. Will keep the 2S2P 3.73V cell and both the 1S5P and 2S5P (3.70V).

Here are two of the previous paragraphs that need correction ...

This failure of the 2S3P cell did not result in an internal short but was significant enough being the primary cause of the extended 12 hrs for the 2S5P pack voltage to go from 2.58V to only 3.74V. An increase on only 1.16V over 12 hrs because of resistance discharging around 0.40 amps.

Should read ...

This failure of the 2S3P cell did not result in an internal short but was significant enough being the primary cause of the extended 12 hrs for the 2S5P pack voltage to go from only 5.16V to 7.48v over 12 hrs. (2.58V to only 3.74V for each 1S5P run). An increase on only 2.32V (1.16V per each of the two p-groups over 12 hrs was because of balance charging which uses resistance discharging around 0.40 amps which is working against the positive charging. If I had balanced charged that 2S5P at 1.5 amps the pack would've accomplished the same task under five hours of elapsed time instead of twelve hours. Still too long indicating all ten of the 30Q cells are suffering from higher than normal self-discharge varying from the best 3.73V cell to the worst 3.44V cell.

When adding up the individual cell voltages of the 1S5P group equals 18.14 volts divided by 5 equals 3.628V and the 2S5P group 18.02V divided by 5 equals 3.604V. That's how a BMS basically sees each p-group in a battery pack, giving no indication how much variance there is between the individual cells giving a false impression they're closer when the individual cell variance may be as great as 0.31V or greater over 44 days (3.75 to 3.44V). Some of you may have noticed that after you charge a pack with a few hundred cycles for winter storage that if you plug in the charger again a month later the red light will come on again and may stay on for several minutes before going green again. The longer the red light stays on is an indication of high self-discharge among one or more p-groups and/or a faulty BMS.

Here's the other paragraph as posted above then edited so hopefully not confusing ...

Isn't it generally assumed that the more cells in a p-group they tend to keep each other balanced with less stress on each individual cell in a p-group? If i would've built a 10S6P 30Q 141 VRUZEND battery pack (instead of only 3P) it's my understanding that instead of nine cells showing higher than normal self-discharge (3.44V-3.70V) there may have only been 4-5 cells with higher than normal self-discharge. And instead of only 20 good cells (3.75V-3.74V) and one other ok cell at 3.73V there would now be 25-26 good cells after 44 days (1/2 to 2/14)

I won't be checking in again until Monday afternoon with final test results ... so doesn't mean i'm ignoring any reply should you post again today as i'm taking a break over the next 2 days to concentrate on these FINAL 4-5 30Q cell tests. Think you'll appreciate that any further UPDATES won't be necessary until July after another 100 cycles with the ten new 30Q "6 KH1T" cells integrated with the other twenty good 30Q "141" cells in my VRUZEND 10S3P battery.

PS:

youre dealing with a slight self discharge

i'm sure Samsung appreciates your perspective :wink:

 

[eMark]

Experimental tests indicate that the storage mAh capacity of the 30Q "141" cell with the highest self-discharge (3.75V to 3.43V from 1/2 to 1/15) does not diminish its ability to store the same capacity as the other twenty good "141" cells (10S3P) showing NO self-discharge from 2/1/21 to 2/14/21 (44 days). It's ability (3.43V cell) after 170 c/d cycles exhibiting the highest self-discharge to still store nearly as much capacity as the new 30Q "6 KH1T" cell would probably even be an understatement to say, "That was unexpected".

Here's the comparison of both cells (older 30Q "141" and new 30Q "6 KH1T" with both being fully charged to 4.20V, then both discharged together beginning at 2.56 amps down to 2.00 amps at 2.50V cut-off, then bounce back voltage after 1 hr rest, then charged again until FULL ...

• 30Q "141" cell manufactured in 2019 with 170 c/d cycles in 2020 = 2,928mAh

• 30Q "6 KH1T" cell manufactured in 2020 with 2 c/d cycles in 2121 = 3092mAh

The charge time to FULL for the older "141" cell from its bounce back voltage after 1 hr rest was 2:45 hr. The charge time to FULL for the new "6 KH1T" from it's bounce back voltage after 1 hr rest was 2:40 hr. Because the bounce back voltage of the new "6 KH1T" cell w/only 2 c/d cycles was greater than that of the older "141" cell (with 170 c/d cycles) it didn't take as much time to reach FULL (2:40 hr) as the older "141" cell to reach FULL (2:45 hr).

It was just coincidence that the received storage voltage of the ten new "6 KH1T" cells at 3.43V was the same as "highest" self discharge voltage of the older "141" cell at 3.43V on 1/15/21 after 14 days from 1/2 to 1/15 (see 1/15 self-discharge chart on p. 1). IMO, not relevant to the above mAh capacity tests of the two cells ... just coincidence.

What is of significance is that my conservative etriking with 170 cycles in 2020 with bottom balancing p-groups within a few mVs before straight charging each of the paralleled 5S3P sub-packs to 20.5V with the co-joined sub-packs (10S3P) discharged on average over 170 c/d cycles to 33.5V (only discharged to Controller cut-off of 32V three times) is why the 3.43V cell, with the highest self-discharge, still has as much storage capacity as it does.

HOWEVER, even with conservative TLC (charge at 1.5A (0.5C to only 41.0V instead of FULL to 42.0V and avg discharge to only 33.5V) of my 10S3P 30Q 141 VRUZEND battery it apparently had no affect what-so-ever in alleviating the unexpected high self-discharge of 9 out of 30 (30%) of the 2019 production run of my 30Q "141" cells. Cells (30Q "141") that i truly believed would be a significant improvement over the previous 30Q "136" production runs from 2014 thru 2018. More than one ES member reported that high self-discharge plagued enough of these 30Q "136" high energy (15A rating) cells as to discourage some from further DIY builds using Samsung's 30Q cell.

 

[goatman]

so the 3.43v cell is still self discharging
how much per day?

 

[eMark]

so the 3.43v cell is still self discharging
how much per day?

Yes, i believe so and will know if still the same or different in two weeks when compared with 1/15 chart on p. 1.

As usual i was still editing my previous post another time shortly after your post. Maybe, want to go back and reread as there were several edits ... so hopefully there aren't any typos or mistakes causing further confusion.

Have set aside a few of the cells with higher self-discharge (as shown on 1/15 chart on p. 1) with resting voltage of 3.75V today. Don't have the list with me, but if my memory serves me they are: The two 3.70V cells, the two 3.53V cells and the one 3.43V cell. All these tests are getting a little old. If you've ever worked with either of the VRUZEND kits you know what a pain it is to hand start those little nuts on the small threaded stud. I've become quite adept at it, but it's still a pain. The threaded stud should have been M4 0.70 as the bus bar holes are just large enuf to accept a M4 0.70 threaded stud.

Will check back tomorrow afternoon (heading home after posting this). In the meantime if you were me would you integrate the ten new 30Q "6 KH1T" cells with the twenty good "141" cells having 170 c/d cycles? They (141 cells w/170 cycles) apparently are "good" cells with no self-discharge over 44 days (1/2 to 2/14). Apparently as much as 94.6% storage capacity (2,938mAh to 3,095mAh) of even the 3.43V cell compared with the ten new 30Q "6 KH1T" cells (although they're not yet broken in which would mean they are capable of more than 3,095mAh capacity as shown in previous post.

 

[goatman]

if it was me, you already have the batteries

10s3p,you have 10"K" cells, id put 1 "K" cell in with 2"141" cells per cell group

from your testing we know the self discharging cells retain their capacity
if youre regularly using the pack, you should be ok

if the pack sits for a month, the self discharging cells will kill the p-group
youre using cells that arent self discharging but could randomly start self discharging

thats why im more curious to see if the 3.44v cell has stopped self discharging
to see if thats a fix for the 30Q

if it is, then its just a matter of doing a pack discharge to 2.5v then charge to 4.2v before putting into storage or every 100 cycles

i guess its just not a cell for the average consumer

 

[eMark]

if it was me, you already have the batteries ...10s3p, you have 10 "K" cells, id put 1 "K" cell in with 2 "141" cells per cell group

Will put the ten new "K" cells in 2P position with ten of the other good cells in 1P & other ten good cells in 3P position ... hopefully by mid-March. Come July will disassemble 10S3P to check cells for any with high self-discharge. I have two UPP batteries for extended travel (20+ miles round trip) and backup when needed.

i'm more curious to see if the 3.44v cell has stopped self discharging

You and me both ... if it's still self-discharging to the extent as before (see 1/5, 1/10, 1/15 charts on p. 1) will know by 3/1 (15 elapsed days).

if it is, then its just a matter of doing a pack discharge to 2.5v then charge to 4.2v before putting into storage or every 100 cycles

Not sure if you understood that there were two ways (2.5V) before charging to FULL. My first experiment was discharging below 2.5V (more than once) so bounce back voltage after 1 hr was only 2.51V. When charged to FULL the capacity was 3,394mAh. The second way was discharging just to 2.5V, then resting an hour for bounce back voltage to settle. Then charge to FULL which resulted in 2,928mAh.

i guess its just not a cell for the average consumer

30Q is not among the best top five high energy cells by this review. Samsung's 25R was selected as the all around best selling 18650 high energy Li-ion ... https://www.18650batterystore.com/pages/best-18650-battery-guide

Among the thirty cells were six "141" third line can codes (I3B9, IEA2, I5E5, I3D2, I3D3, I2C4) the majority of the cells suffering from high self-discharge were IEA2 & I5E5. Makes me think it's a QC problem. Some of the good "141" cells also had these two codes. The original order was 50 with some used for flashlight and only six unused "141" cells leftover from the original order in 11/19. Actually, i'm not all that disappointed that they sent me ten 30Q "KH1T" cells instead of ten "141" cells. After 100 more cycles (July) will be lookin' forward to disassembling this integrated 30Q 10S3P pack to see how many (if any) more cells suffer again from high self-discharge.

All ten "KH1T" cells have the same metal can third line code (G459).

Overall, i'm pleased with the VRUZEND kit for experimental learning and if i had to do it all over again would have done the same to see if 30Q "141" still had self-discharge, but never thought 30% of the cells in my 10S3P pack would suffer from high self-discharge. In a way it's OK as I'd be bored this winter if i didn't have a problem solving project with something to fix/repair.

Last but not least the reason i had to remove the pink tube labels is for ease of cell removal from the caps. Otherwise they fit so tight with the tube label it's difficult to remove them from the cap. The 30Qs still fit tight enough without the tube label ... one only needs to snug the barrel bolts to keep the caps' stainless steel inner contact fully compressed against the head of the threaded stud. Even without the pink tube label both the top and bottom end of these 30Q cells is 18.26mm.

The attached photo is an example of an experimental IR test that lends itself to the VRUZEND kits (it ain't pretty, but gets the job done). Used the SM8124A 4-wire Battery Analyzer to check IR of the VRUZEND caps with cell to outer hole of the two stainless steel bus bars. The total IR is 28.4mΩ from the outer bus bar hole on the anode end to the outer bus bar hole on the cathode end. The IR of just the 3.44V "141" cell alone (3.74V and 62°F) from anode can end to cathode cap end is 13.2mΩ. The IR of the "KH1T" cell (3.74V and 60°F) was 18mΩ. Would have expected the new "K" cell to have lower IR than the used "141" cell having the the highest self-discharge of the thirty 10S3P 30Q 141 cells with 170 cycles. The IR of the SS bus bar between hole to hole OC is 5.4mΩ. The IR of the Ni/Cu bus bar from hole to hole OC is 4.2mΩ.

 

[eMark]

That infamous cell 2S3P, 3.43/.44V (5S3P Sub-Pack 1) that I thought was history still has life. Apparently those two DOD experiments (after first charging to 4.2V) have apparently reversed its high rate of self-discharge. One DOD was to discharge below 2.5V until the bounce back voltage was only 2.51V after a 1 hr rest. Then charge to 4.2V resulting in 3,394mAh capacity. This was followed a day later by another DOD to 2.5V and then wait 1 hr for bounce back to settle. Then charge to 4.2V resulting 2,928mah capacity. On 2/15 it was discharged to 3.75V and from 2/16 to 2/19 remained at 3.74V.

Today (2/20) it was down only 0.01V to 3.73V ... overall a major improvement from 1/2 to 1/5 when it's voltage dropped from 3.75/.74V to 3.68V over just 3 days, then down to 3.56V on 1/10 and only 3.43/4V on 1/15. This was the one 30Q 141 cell out of thirty (10S3P) suffering from the highest rate of self-discharge.

Of the five 30Q 141 cells that were still at 3.75 volts from 1/2 to 1/15 three out of five were still at 3.75V with the other two at 3.74 volts on 2/20. Of the fifteen 30Q 141 cells that were 3.74 volts from 1/2 to 1/15, eleven are still (2/20) at 3.74 volts with three down 0.01V to 3.73 volts and the other down 0.02V to 3.72 volts on 2/20 (see chart <img="https://endless-sphere.com/forums/download/file.php?id=286882" alt="January 15, 2021)

Decided to continue doing a similar DOD routine on four more of the 30Q 141 cells suffering from high self-discharge from 1/2 to 1/15 (3.66V, 3.68V, 3.62V, 3.57V). See 1/15 chart for their location in the two 5S3P Sub-Packs ... <img="https://endless-sphere.com/forums/download/file.php?id=286882" alt="January 15, 2021 ... Will report end of month results as far as any reversing of high rate of self-discharge of these four cells ... as well as the not so longer infamous 5S3P cell in Sub-Pack 1.

Should have mentioned before that when i removed the tube labels (for ease of removable from VRUZEND caps) I added a self-adhesive insulator ring to each cell. For those that may not know the entire can is negative, even the top circumference surrounding the positive cathode cap. Although the VRUZEND cap contact design is such that a short shouldn't happen an insulator ring is still a must. That white one was with the tube label.

typo correction: 2/1 to 2/15 corrected to 1/2 to 1/15

 

[goatman]

my battery guy has 300- 30Q from faulty packs, i agreed to buy 80 from him to try the "desulfate" thing on them.
ill be able to share the results,
if it works ill buy all of them

 

[eMark]

my battery guy has 300- 30Q from faulty packs, i agreed to buy 80 from him to try the "desulfate" thing on them.
ill be able to share the results,
if it works ill buy all of them

Do you have any idea how labor intensive and time consuming is my "de-selfdischarging" routine?

Hopefully, you can devise a procedure to speed up my slow-going routine. Wouldn't have stumbled upon the "de-selfdischarge" routine without the use of the MiBOXER C4, and my homemade discharger (salvaged 12V bulbs from U Pull R Parts). Routine: Charge to FULL then discharge to 2.5V (and lower), then charge to 3.75V (or other storage voltage) and daily check for any self-discharge.

Channel 4 is the only channel (MiBOXER C4) that can discharge after FULL charge so could only test one cell at a time. Early on decided to use my homemade discharger (1.25A discharge) as MiBOXER 0.40A discharge rate takes forever. Even 1.25A rate takes too long from 4.20V to 2.50V (and lower). A faster discharge rate may still accomplish the same "de-selfdischarge" result, but for how long ??? Hopefully, you can provide encouraging results that are less time consuming when you start testing your 30Q faulty packs. You'll have to first disassemble the packs to separate the good cells from the cells suffering from high self-discharge. The good cells should be in the majority assuming you can devise a test to determine the good from the not-so-good. If it were me I'd discard the worst cells and not even spend time "deselfdischarging" the other cells suffering from high self-discharge ... as it's a time consuming procedure.

This morning I drained the 3.56V cell (1.25A discharge rate) to empty (0.00V) using my homemade discharger (and there was still decent bounce back. Then charged to FULL at 1.5A using MiBOXER. What was interesting is that the IR was 33mΩ through the complete charge. The IR on the other cells (previous tests) with high self-discharge would always start out somewhere between 80-70mΩ and wouldn't drop to around 33mΩ until 95-97% Full. IMO, the MiBOXER reads high (33mΩ) compared to my HTRC Balance Charger IR function (24mΩ) and the AideTek SM8124A 4-wire reading of only 12.6mΩ. Took these three different readings (one after another) of said "3.56V" 30Q cell at 4.20V earlier today.

Will summarize "de-selfdischarge" results Monday afternoon, March 1st ... as well as the twenty good 30Q cells voltage from 1/2 (3.75V/3.74V to 3/1/21 (...../.....).

 

[goatman]

i can do bulk testing within reason with my battery tester or ebike

if i want to do 1s5p, i discharge and charge at 3amps(0.6amps/cell) in 11 hours

can do an entire bike pack in 11hrs

heres 5p of 30Q-136 at 1.97v, i can charge/discharge/charge (4.2v/2.5v/4.2v) in about 16hrs

 

[eMark]

Will be interesting if your procedure also provides a "fix" even if just temporary. Are you going to disassemble the packs so you can determine which are the good 30Q (136) cells and which ones suffer from high self-discharge? If two-thirds of the cells in your packs are good i'd just salvage the good cells and dispose of the not-so-good cells at a recycle center. At first it's an interesting challenge, but being labor intensive and time consuming i'm not looking forward to disassembly and retesting the twenty "141" cells and ten "6 KH1T" cells after 100 more cycles come July.

My "de-selfdischarge" routine is more likely a temporary fix. There is no way i'd reassemble those nine "141" cells, that now seem OK, back into my 10S3P 30Q "141" pack. Found this thread of some interest. Generally agree that it's best to dispose of high self-discharge 30Q cells at a recycle center.

https://www.candlepowerforums.com/vb/showthread.php?444518-18650-high-self-discharge-cell-becomes-fine-again ... see post #11, #12 "Out of 9 button-top 30Q cells I bought there, 3 have gone bad (or are going bad)."

My experimental testing was in a dry environment with temp 60-62 ℉. Come summer with humidity and higher temps those cells could again go into a self-discharge mode. It's not a concern when i bottom balance before bulk charging my 10S3P every other day or and often the same day.

Still undecided how long i'll keep those nine 30Q 141 cells that seem OK now to see if they again revert to a higher than normal self-discharge. Would like to get them out-of-site ... out-of-mind. Am pleasantly surprised that twenty of the 30Q 141 cells have little to no self-discharge after 44 days (1/2 to 2/15).

 

[eMark]

so the 3.43v cell is still self discharging
how much per day?

That 3.43v cell was the one cell out of ten with the highest self-discharge that we used for experimenting with deep discharges in February as a possible "fix" or at least minimize s-d.

• charge to 4.20v, deep discharge so only 2.51 resting volts after 1 hr, then 4.20V charge (3,394mAh), then discharge to 3.75V and track self-discharge rate. Again, discharge this time to 2.50V with bounce back 3.35V after 3 hrs, charge to 4.20V (2,928mAh), discharge to 3.75V and track any self-dscharge.

This morning (3/1) that 3.43V cell was down only 0.03V at 3.72V from 3.75V on 2/15. So those deep discharges greatly reduced it's previous high rate of self-discharge of 0.32V from 1/2 (3.75V) to 1/15 (3.43V). More research is needed to determine if a deep DoD is actually good for a 30Q pack or just for those cells suffering from a higher rate of self-discharge than considered normal for 30Q cells. More research is needed on usefulness of a deep discharge (e.g. once a month) for entire 30Q pack suffering from moderate to high self-discharge.

Minimal self-discharge on 20 good 30Q cells in the 10S3P Vruzend pack from 1/15 to 3/1 ...

• 5 still at 3.75V from 1/15 to 3/1
  11 of 15 still at 3.74V from 1/15 to 3/1
  3 of 15 from 3.74V on 1/15 to 3.73V on 3/1
  1 of 15 from 3.74V on 1/15 to 3.72V on 3/1

Of the 10 cells suffering from unacceptable (moderate to high) self-discharge they all showed improvement with a deep discharge routine like that with the 3.43/44V cell suffering from the highest self-discharge of the 10 cells shown in the 1/15 chart ...

 

[goatman]

i dont follow the general consensus of discharging a cell at low amps will increase its lifecycle, the majority yes but not all

30Q and 40T are different than others

take a look at my testing

30Q and 40T are the only cells ive found that like to continuously cycle, other cell cells will lose half their lifecycle
40T shares the self discharging
https://endless-sphere.com/forums/viewtopic.php?f=14&t=107895

after 515 cycles the 40T was capacity tested during cycling

the very first discharge of the cycling test was
#1 3180mah
#515 2977 mah
if i capacity tested right now it would probably jump to 3000mah for #516

when you first discharge a new cell it will lose alot of capacity over its first 50 to 100 cycles
i think thats part of the development of the SEI layer

so im wondering if by discharging to 2.5v and charging back up to 4.2v, its doing something like restoring the SEI layer

look at the 30Q, after the capacity test it behaves like a new cell

#1 d-2519, c-2489
#50 d-2428, c-2392
#100 d-2395, c-2355
0.6amp capacity test, #1-3170mah, #100- 3092mah. 78 mah loss
#101 d-2542, c-2501
#156 d-2395, c-2353
#157 d-2395, c-2352
#200 d-2372, c-2329
#200 d-3026, c-2863 capacity test
#201 d-2497, c-2453
#241 d-2312, c-2265
while doing capacity test, we had a power outage in the middle of test. test stopped and resumed so i just added the numbers together,
d-2992, c-2830 didnt like the curve so did another capacity test
d-3045, c-

#243 d-2394, c-2352
#244 d-2388, c-2343
#245 d-2380, c- charged to 3.79v. dec.19 and put on shelf. i think im done testing

so if everyone thats running these cells at low amps, low temperatures and if they have a bms that shuts down at 3.0v are probably killing them

i dont mind if i need to discharge to 2.5v every 100 cycles as maintenance or before putting into storage

 

[eMark]

30Q and 40T are the only cells ive found that like to continuously cycle, other cells will lose half their lifecycle... https://endless-sphere.com/forums/viewtopic.php?f=14&t=109601

Isn't that generally true with all high drain energy density cells? Has any DIY builder ever reported high self-discharge with VTC6 (3000mAh 15A rating)? The only problem is the price ($7.99) compared to $4.99 for 30Q cell (probably why few, if any, VTC6 DIY builds). IMO, the reason VTC6 costs $3 more than 30Q is first rate QC (Japan's rigid standards whether cars, medical or Li-ion cells) with the result apparently no reports of VTC6 suffering from high self-discharge ...

• A lithium battery usually loses only about 5% of its life span after charging for a month. If not in use, charge it every few months to prevent battery aging ... https://www.lazada.sg/products/sony-murata-vtc6-30a-3000mah-18650-rechargeable-li-ion-battery-1pcs-i326884981.html

Even though China and Singapore manufacture the VTC6, Japan's zero tolerance for defects is still the norm. Thus, why Tesla uses Panasonic. If only Vruzend would introduce a 21700A kit for Pan/Tesla NCR21700A (12-14mΩ)... http://queenbattery.com.cn/984-thickbox_default/panasonic-21700-21700a-ncr21700a-5000mah-battery-cell.jpg

i don't mind if i need to discharge to 2.5v every 100 cycles as maintenance or before putting into storage.

Your not recommending discharging to 2.5v "before putting into storage? The resting storage voltage after a discharge to 2.5v at best may only be 3.5v.

Starting to reassemble my split 10S3P 30Q 141/KH1T pack. This morning one of the 30Q "KH1T" cells showed signs of high self-discharge. Will use the "141" 3.73v cell in its place with self-discharge of only 0.02v from 1/2 to 1/15; whereas the 30Q "KH1T" cell had a discharge of 0.05v in just 3 days.

Am getting fairly decent at disassembly and assembly of my Vruzend experimental split pack 10S3P 30Q . Actually, looking forward to July (f not sooner) when I can at least remove all bus bars to check individual cell voltages and report if (and how many) more cells are once again suffering from high self-discharge.

 

[goatman]

no to storing at 2.5v

 

[eMark]

no to storing at 2.5v

What thread are you using to post your findings on the number of cells in your 1s70p 7-day voltage leveling experiment that suffer from high self-discharge having disassembled the 1s70p to check individual cell voltages after resting for another 7 days?

Are you planning to discharge the problematic cells to 2.5v to see what affect your research has on minimizing self-discharge after recharging 1s70p (5s14p) to nominal voltage, 4.1v, 4.2v or whatever voltage you use for storage? Then disassemble 5s14p again and check individual cell voltages after 7 days and share results :thumb:

 

[goatman]

i might gather what im doing with that pack build into 1 simple thread, 2 out of the 70 were at 3.505v after separating from equalizing the other 68 were at 3.498v

i made 17s4p and before paralleling each string was 59.6v

now im going to desulfate the pack twice and put it to use

 

[eMark]

Had to partially disassemble Sub Pack 1 in order replace 1 of the ten brand new "KH1T" 30Q cells (?culls?) because of its high self-discharge. The other nine "KH1T" 30Q cells are OK (so far). The "KH1T" replacement cells are all placed in the middle (between 1-3) of each 3P group. Reassembled Sub-Pack 1 yesterday after removing the one bad "KH1T" cell and replacing with the 2S2P from Sub-Pack 1 (3.73v) as it was the 1 cell out of the ten suffering the least from self-discharge having only 0.02v discharge from 1/2-1/15/21.

The other twenty good 30Q 141 cells (10S3P) showed no self-discharge whatsoever over 44 days.

Now with good cells in all ten 3P-groups the average P-group IR is 4-5mO. Hoping that after 100 more cycles in 2021 (170 cycles in 2020) the twenty good cells are all still good ... but time will tell as to the condition of the nine "KH1T" 30Q cells come July/August. If everything still looks good may wait until Nov/Dec to once again disassemble the Vruzend 10S3P 30Q to once again test each individual cell for any higher self-discharge than normal (like in the above 1/15/21 chart).

Note: Had ordered ten new 30Q "141" from IMR, but was sent ten "KH1T" 30Q cells instead. My only explanation is that IMR may only ship 30Q 141 cells in larger quantities. They possibly thought I was purchasing only ten for flashlight or UknowWhat instead of replacing bad cells in my Vruzend 10S3P 30Q DIY pack suffering from high self-discharge. All 30 cells had an IR of 12.4-12.6mO with my AideTek SM8124A IR Tester ... https://www.amazon.com/AideTek-Portable-Internal-Resistance-Voltmeter/dp/B01L6IC8A4

 

[eMark]

FWIW, the ten 30Q "KH1T" new cells (?culls") were shipped/recd 12/20 at 3.46v. The 20/21 good 30Q "141" cells purchased in 11/19 (170 10S3P pack cycles in 2020) were shipped/recd at 3.40v.

All 30 cells were balanced at 3.74v before reassembling the Vruzend 10S3P 30Q "141/KH1T" experimental pack last week with 3 cycles so far in 2021 ... it's snowing today with daytime highs in the 40s the rest of the week.

Do not use a BMS! Will continue to bottom balance with a combination of balance charging and straight (bulk) charging (experimental), and top balancing if necessary. Always bottom balance all ten p-groups to same voltage (e.g. 3.45v) after at least a 1-2 hr rest if not longer.

 

[eMark]

Something that needs to be said again is that even "high" self discharge (leak) doesn't diminish the potential capacity of a 30Q cell once it is balanced (equalized) with other 30Q cells and bulk charged to FULL (4.2V). As BlueSeas previously expressed packs that may have cells that suffer from even "high" self-discharge goes "largely unreported". ESPECIALLY, with a pack that is charged every other day as any "high" self-discharge usually isn't noticeable until at least 5 days with a resting pack ...

The observed phenomenon of high self discharge may be true for many cells, and further may go largely unreported. Especially if the charge process has an effective balancing routine to rebalance the pack.

But that self discharge, in paralleled groups of cells, with no routine balancing eventually shows up once any self discharge sets in. That cell or cells become "low" and are constrained by the high cells calling for end of charge. This self discharge isn't by itself in most cases isn't a reason to trash the pack...or even the cell. But does require some degree of balancing.

"constrained by the high cells calling for end of charge" ... thus the advantage of first bottom balancing (say 1.2-1.5 amp charge) the p-groups before bulk charging followed by top discharge balancing via a BMS (if you use a BMS, i don't). Top discharge balancing via a BMS is very slow (0.40amp rate, if even that much).

Doubt that there were more than 4-5 times that my 10S3P pack rested for more than even 2 days between discharge-to-charge in 2020. In the following chart there are only 3-4 cells with noticeable self-discharge over 10 days that i would have recognized as a p-group that was possibly suffering from self-discharge. The following chart shows the eight cells suffering from various levels of self-discharge.

The following cells in Sub-Pack 2 (1S-1P, 4S2P, 5S2-P) were all at 3.70V on 1/22/21 due to self-discharge from 1/2. After charging each to FULL (4.20V) last week i then discharged them at 1.25amp to: 2.50V (1S-1P), 2.98V (4S-2P), and 3.45V (5S-2P). Then charged to FULL again followed by discharging each to 3.75 resting volts on 3/17. After 4-5 days all three are still at 3.75 volts. That is not to say that they won't self-discharge over the next 10 days (April 1st ). As BlueSeas implies high self-discharge is only a concern during longer periods between discharge-to-charge and long term storage. After storage or even a weekly rest the p-groups should be equalized ... preferably via bottom balancing (IMO) before bulk charging.

The following chart shows the amount of cell discharge in my experimental 10S3P Vruzend pack from 1/2 to 1/10. The other two photos are my method for bottom balancing the p-groups before bulk charging. This is even more important with 30Q cells that are more prone to self-discharge than other high energy dense cells. Just because there is a leakage of capacity doesn't mean that the capacity can't be restored. When the leak is slow it's apparently no big deal when a pack is discharged and charged often (every 2-3 days).

 

[kdog]

I was hoping I'd dodged the 30q internal short issue on my 2kwh pack (21s10p) .... But no. . It's ~4yrs old and has had a couple of hundred cycles. A cell group started showing signs of trouble after about 50cycles. initially I thought it might be just variance in the bms (adaptto) but cell group10 has slowly and steadily deteriorated, now the bms can't balance as fast as the self discharge until it's nearly flat. Not looking forward to the repair as it was a complicated build.
Im half thinking of just building a whole new battery, but then should the adaptto will die, it'll be more battery surgery (bc of the proprietary bms)
Might just hack out the group and replace it with something vaguely compatible.
Sad bc it was such a sweet pack, has been a work horse for me. It's put out over 153kwh, and towed or blasted it's way through 6000kms. Sniff maybe it'll survive the surgery

 

[eMark]

Might just hack out the group and replace it with something vaguely compatible. ... Sad bc it was such a sweet pack, has been a work horse for me. ... Sniff maybe it'll survive the surgery

I'd be tempted to disassemble the entire pack. Test all the cells ... remove 21 of the 210 30q cells (10%) suffering from higher than normal self-discharge ... then reassemble as a 21s9p ... a new 21s10p pack is even more expensive now that cells cost more.

Being retired such a dismantling project would keep me from getting bored during a cold Minnesota winter. The 2nd build is easier (faster) then the 1st build, so they say. Even if you decide to build a new 21s10p i'd still disassemble the used 21s10p 30q pack to salvage the useful cells for another backup build (21s9p or 21s8p).

Let us know the end result of your "hack out the group" and replacement. GOOD GOING whatever way(s) you GO :thumb:

 

[eMark]

Eighty-five more cycles since mid-March 2021 to July 22, 2021 for a total of 235 charge/discharge cycles including 150 cycles (not 175) from mid-March to mid-November of 2020. Following is the previous chart with twenty “141” cells having no significant self-discharge over 44 days; while the other ten “141” cells suffered from some degree of self-discharge over 14 days (1/2/21 to 1/15/21) ...

Twenty of these thirty “141” cells showed no self-discharge from 3.75v/3.74v over 44 days (from 1/2/21 to 2/14/21), and were reassembled in the following two 5s3p Sub-Packs as shown below …

141--141--141--141--141.......141--141--141--141--141
.K.....K.....K.....K....141.........K....K.....K.....K.....K
141--141--141--141--141.......141--141--141--141--141

Three of these current p-groups suffer from higher than normal self-discharge (blue p-groups), but not so serious to disassemble the pack at this time. One of the ten new “KH1T” cells was defective so replaced it in the “K” file with one of the “141” cells. The defective K cell was because of what appeared to be a very small puncture of the can wall which was only visible after removing it’s protective shrink wrap. Further testing indicated a significant self-discharge so it was replaced with the 141 cell with the least self-discharge (Sub-Pack 1 2S-2P) of the ten high-lighted cells from 1/2/21 to 1/15/21. All ten of the “K” cells were from the same manufacturing run having the same identical codes on the metal can.

Because 30Q packs are known to suffer from self-discharge, more than other high energy cells, I [attempt to] bottom balance the p-groups within ±0.005v before bulk/straight charging at 0.5C from 40.1v to 41.1v depending on my journey. I'd say average discharge cycle after one hour rest is between 35v to 36v. Self-discharge isn’t a noticeable problem when you are using (recharging and rebalancing) the battery pack as often as every day or every other day. BlueSeas makes a valid point ...

The observed phenomenon of high self discharge may be true for many cells, and further may go largely unreported. Especially if the charge process has an effective balancing routine to rebalance the pack.

This self discharge isn't a reason to trash pack...or even the cell. But does require some degree of balancing.

More than one DIYer has experienced self-discharge problems so severe with 30Q to the point of the following (valid) post by madin88, also on page 1 of this thread …

I had to trash batteries where i used 30Q cells because of self discharge and know about others who had similar issues with that cell.

One pack i was trying to manually balance by charging up all groups which had lower voltage, but after 2-3 month it was quasi unusable again because the BMS did cut off whereas controller was still showing 30-50% SOC, which means that one group went below 2,5V where the highest still had above 3,6V or so.

I also found out that self discharge depends on the actual voltage of the cell and it could be that lets say at 4,1V it will discharge very quick to 3,8V for instance and then almost stops.

It was always those packs built with 30Q where this happened and since i noticed that i don't use this cell any longer.

It's too early at this stage to know whether the 3 p-groups in the above 30Q pack diagram (in blue type) with higher than 'normal' self-discharge is due to just one cell or more than one (141 and K ?) among these three p-groups. Come further testing in December there may be more than just these 3 p-groups suffering from self-discharge of some concern . Should accumulate at least another 50-60 cycles on this Vruzend experimental 30Q battery pack between now and mid-October. Have another experimental project from mid-Oct thru mid-Nov.

Will disassemble this experimental Vruzend 10S3P 30Q pack again this winter to test individual cells for degree of self-discharge. The reason for the two 5S3P Sub-Packs is to monitor p-group voltages with my 2S-6S Balance Charger during bulk/straight charging. Also check IR of paralleled 30Q p-groups (5S6P) during 5S charging. IR of 4-5mΩ when paralleled as 5S6P for bulk/straight charging with HTRC C240 Duo with 235 c/d cycles to date so far.

P.S.: FWIW, I don't use a BMS ... i bottom balance before bulk charging and closely monitor my experimental pack.