"desulfate" 40T and 30Q and VTC6 and P42a

[goatman]

its been awhile to remember waaay back in april

[quoteHow low was your discharge amperage to from 4.10v to 3.185v on april 15 ? Did you record equalized voltage at 3.185v ASAP before any bounce back voltage? Do april 30 voltage readings represent the bounce back voltage from 3.185v ?
][/quote]

that would be bounce back

This time you equalized cell voltages close to 3.192v with three notable exceptions (3.198, 3,198, 3.197). The best performer being 7s. How many days were these cells equalized (evidently not 1 month as with pack 2) before recording the above equalized voltages ? How do you account for two cells at 3.198v and 1 cell at 3.197v ?

only a couple days

pack 3 i never did put to use yet, its still just sitting there on the table
just checked the voltages



i just grab the cells and equalize them with each other
some might of been 3.8v others as low as 3.0v
like in this thread
https://endless-sphere.com/forums/viewtopic.php?f=14&t=112570#p1665165

[quoteDo you yet have an opinion on whether discharging to 2.5v or 3.0v or 3.185v gives better results (regenerate) to minimizing self-discharge ? How did you happen to settle on 3.192v. Is that the cut-off voltage of your controller?

Do you think if more 30Q battery packs were discharged to 3.20V before recharging again to 4.10v that self-discharge would be less of a problem with energy dense cells ?][/quote]

i think taking them to 2.5v every 100 or so cycles or before putting them in storage with an active cell balancer is all you need.

the sony vtc6 i havent touched since the previous post and they equalized really well and are holding steadt still

 

[eMark]

i checked the 17s4p pack,
on april.01 i had drained it down to 51v/3.0v per cell with a 0.5amp cut off
all series groups are sitting at 3.185v except for
S-group 10 3.186v
S-group 6 3.184v

For salvaged 30Q 136 cells possibly costing you no more than $1 ea. its almost too much to fathom that since May 31th thru August 11th, that eight of the 4p-groups (17s4p) haven't lost so much as even 1mV, and the remaining nine 4p-groups' with minimal self-discharge ranging from only -1mV to -6mV (May 31st thru August 11th).

Who said that salvaged 30Q cells couldn't be cured of unacceptable self-discharge; while resting/storage for at least for 73 days

Is that a special Samsung 30Q DMM :wink: that you used yesterday to take your most recent 30Q voltages to the nearest mV ?

Having reflected on this almost unbelievable achievement from April 30th to May 30, and what would seem even more remarkable from May 31th thru August 11th HOW DO YOU account for such exceptional success ... seriously (kidding aside) ???

For example the fact that the equalized cells (relaxed state) in your following chart actually ended up with a gain in positive voltage (++++.033v to ++++.043v), with NO loss of voltage (due to self-discharge) on may 30 ... on the contrary at least ++++.033v and more after one month ... having been somewhat equalized on april 30.

pack 3

april.30........may.11.....may.30
1s-3.192.......3.221,,,,,,3.228++++.036v
2s-3.198.......3.221......3.235++++.037v
3s-3.185.......3.207......3.216++++.031v
4s-3.185.......3.207......3.220++++.035v
5s-3.192.......3.221......3.229++++.037v
6s-3.198.......3.221......3.235++++.037v
7s-3.192.......3.221......3.235++++.043v
8s-3.192.......3.220......3.228++++.036v
9s-3.192.......3.221......3.231++++.039v
10s-3.192......3.220......3.228++++.036v
11s-3.192......3.214......3.227++++.035v
12s-3.198......3.221......3.235++++.037v
13s-3.191......3.214......3.224++++.033v
14s-3.192......3.214......3.228++++.036v
15s-3.192......3.220......3.228++++.036v
16s-3.192......3.217......3.228++++.036v
17s-3.197......3.221......3.235++++.038v

Perhaps, the reason no one besides me has replied since your post on May 31st is that like me they wondered how in the world can there be an increase in voltage when all the p-groups have supposedly been equalized (relaxed resting voltages). Weren't we expecting at least some self-discharge from these salvaged cells, if only in mV from april 30 to may 30 ? Yet the opposite is the case with an increase of millivolts ranging from ++++.033v to ++++.043v.

Maybe, it needs to be pointed out the difference between recording the 68 individual cell voltages or p-group voltages in a 17s4p pack within a few minutes (ASAP) after being somewhat equalized via discharge voltage ("drained it down to 51v/3.0v per cell with a 0.5amp cut off) ... AND ... the same pack being equalized with all 68 cell voltages relaxed and resting (at least the usable cells) after being ... "drained it down to 51v/3.0v per cell with a 0.5amp cut off" and individual cell voltages or p-group voltages only recorded several hours or a day later after sufficient rest/relaxing.

 

[goatman]

most likely my delightful sense of humor keeps most people away
its just bounce back voltage
i just grabbed my ebc-a20 battery tester and touch the nickel tabs that are for connecting a bms or balancer, atleast its giving consistent readings.

the reason i like the 30Q and 40T is they like to run steady charge/discharge/charge/discharge with no breaks while that will kill other cells. lets say a 30Q does start to self discharge and you use an active balancer, i think youre less likely to kill that cell during micro-cycling

should check the voltages of the vtc6 cells and see where there at

 

[eMark]

IMO the real reason your p-groups (1s-17s) show such minimal discharge is because of their low voltage (e.g. 3.235v to 3.216v). That's one reason why we don't see self-discharge with new cells like the 30Q "141"and "K" cells received and tested at 3.40v.

Charge your 30Q 17s4p pack to 68.85v (4.05v/cell), let rest for a day before recording the seventeen 4p group voltages. Then record p-group voltages 10 days later. That's a much better guage of any self-discharge than attemting to determne at their present low SoC (but you knew that already :wink: ).

Self-discharge gradually falls off towards zero as the SoC percent goes to zero. At the high end (4.2v) self-discharge increased more rapidly over 80% SoC (4.0v). The SoC percent has a very large impact on self-discharge. Thus why your low voltages are unable to distinguish the bad cells with unacceptable self-discharge from the good cells. So it's questionable if your research (thus far) has "regenerated" those salvaged 30Q cells. You need to do more testing like at 80% SoC, rest/relax seventeen p-groups for 24 hours and then record any self-discharge of the p-groups 10 days later :thumb:

If you really want to use a better gauge of your cells more realistic degree of self-discharge you need a higher SoC. At least 3.89v per p-group or 80% with all seventeen 4p groups equalized ABAP at 4.0v, rest/relax for 24 hrs and record resting voltages of p-groups 7 days later and 14 days later. This is a better test for separating the men from the boys than equalizing a your low voltage. That's assuming you really want to know the degree of self-discharge. That requires that you disassemble the pack after 14 days and measure voltage of all 68 cells. We can see that the "error band" appears to be slightly less than 1mV.

Before you put your 17s4p pack to use charge it to 80%, then let p-groups rest/relax for at least 5 days to get some idea of the self-discharge variance among the seventeen 4p-groups. This will give you a better idea of the actual self-discharge condition of your 17s4p pack. Record p-groups voltages again after 10 days.

 

[goatman]

i did not know that
ill charge them up
the vtc6
the block of 22 cells are all at 3.950v
the block of 66 are at 3.951v
ill see how they hold up at the same time as the 30q

 

[eMark]

desulfating does something to the discharge curve and brings back capacity for about 50 cycles so when you had the self discharging cells it was the perfect opportunity to see what happens when you desulfate them

i dont know the history of the cells other than the packs were considered garbage, unfixable, group voltages all over the map

what im looking at with these cells is to see if desulfating them every 50 or 100 cycles as maintenance will refurbish them as usable

im looking for a battery that can continuously discharge/charge without suffering lifecycle loss and thats the 30Q

Ouch, i think i went blind from reading ”desulfate” a trillion times in this lithium battery thread. Can’t you just call it regenerate or something else not totally unrelated to what you’re doing?

Finally! we got the word to call it

From your **regenerative** tests on those salvaged 30Q cells ("considered garbage, unfixable") have you been able to achieve what you'd consider a lessor (more acceptable) rate of self-discharge? Enough so to build an experimental pack of **regenerative** cells for further testing? How many of the cells in that 17S4P pack were you able to **regenerate** enuf to use for at least a 10S5P 30Q build for further experimental c/d cycle testing?

It's coming up on 4 months since your last post on August 13th on 30Q (and VTC6) cells you're attempting to **regenerate** for suitable application. Assuming your 17S4P pack are 30Q cells salvaged cells and not VTC6 salvaged cells.

https://endless-sphere.com/forums/download/file.php?id=289173
https://endless-sphere.com/forums/download/file.php?id=294392
https://endless-sphere.com/forums/download/file.php?id=294429

How many of the those cells (e.g. 17S4P) were you able to **regenerate** enuf to make it worthwhile to continue with an experimental build (e.g. 10S5P) for further testing of what you consider *regenerative** 30Q cells ?

 

[goatman]

i built 3 packs of 30q, 2 i use all the time and theyre doing just fine except for the pack i used 5mm square magnets on.

pack 3 has just been sitting there doing nothing :lol:
just measured the voltages



previous numbers, a couple have dropped

 

[eMark]

pack 3 has just been sitting there doing nothing :lol:
just measured the voltages

All seventeen (4p groups) ("just measured the voltages") ++++ gained an increase in voltage ranging from 31mV to 43mV from April 30 to May 30 according to your posted records. That's EXCEPTIONAL for those 68 white, yellow and blue label shrink wrap cells in that 17s4p pack of [mixed?] cells to actually gain 31mV to 43 mV while resting from Apr 30 to May 30 ...

From May 30th to December 10th only five of those 17s strings had any measurable OCV self-discharge being: 4s, 5s, 17s loss of only 1mV and 9s, 13s loss of 3mV. The other twelve series strings of the 4p groups still had the same increase in voltage ranging from 31mV to 43mV from April 30th to December 10th ... that's beyond EXCEPTIONAL even for some new cells, but you accomplished your **regenerative** feat with [used?] VTC6 cells. You're *regenerative** accomplishment should be worthy of ES MAN of the year :thumb:

You need to share your EXCEPTIONAL **regenerative** procedure for achieving an OCV loss of only 1mV to 3mV in just 5 of the 17 series strings from May 30th to December 10th. Just as impressive is achieving an increase in mV (31mV to 43mV) over a months' rest from April 30th to May 30th. Your **regenerative** (desulfating) exceeds 18650 industry standards for determining an acceptable 10 day Delta-OCV when testing newly manufactured cells for separating good cells from bad cells according to the following chart ...

We know that charging as well as discharging causes a cells' voltage to redistribute itself taking several hours if not 9 days (industry 18650 benchmark?) to return to an equilibrium state again. This is important in 18650 cell manufacture as self-discharge testing follows soon after cell formation. During formation, charging and discharging cycles are applied to a freshly assembled cell. Thus, the charge is not at equilibrium for 9 days (industry benchmark?).

When the cells are finally rested (after 9 days?) their charge is at equilibrium again, the OCV loss rate becomes constant, due only to a cells' self-discharge. For the 18650 cells tested in the above chart example, they were subjected to moderate charging then rested for 9 days. The 10 day OCV exponential loss rate is shown in the above diagram for seprating good cells from bad cells.

ill charge them up
the vtc6
the block of 22 cells are all at 3.950v
the block of 66 are at 3.951v
ill see how they hold up at the same time as the 30q

Were you going to share any OCV self-discharge (if any) of your **regenerative** tests after first recording the charge voltages (3.950V of 22 VTC6 cells and 3.95V of 66 VTC6 cells) after your cell rest timeline? Then record any OCV self-discharge (mV) after 5 days, 10 days, 30 days? What was your rest timeline after charging (3.950V and 3.951V)? What was your first elapsed timeline for first measurement of OCV voltage after say 5 days? How many of those 88 VTC6 cells are still above 3.900V since their recorded voltage (3.950V & 3.951V) on your August 13th post ?

Being that you haven't posted any OCV of those 88 cells since August 13th can we assume there has been no OCV self-discharge during November and possibly not even 1mV loss as of 12/10 ?

 

[goatman]

the vtc6 were holding steady with no discharge at all
about a month ago i paralleled 44-30q to them so that all my remaining loose cells were at the same resting voltage because
i was reading somewhere that active cell balancers need to be connected to a perfectly balanced pack before connecting the balancer or you might fry a circuit. i ordered some balancers but wound up making a 15s2p back pack battery for my euc before it showed up. ill open up that pack and see how their doing when that 15s balancer shows up

the increase in voltage of the 30q's was just bounce back

i think you mentioned before that self discharge happens more at higher voltages, maybe a person just needs to store their 30Q's at 3.2v instead of 3.7v?

the 5mm square magnet battery ill be stripping down and rebuilding with 7mm ring magnets and an active balancer

it wouldnt be hard to do a regenerative cycle every month on these by just running down your pack while riding at low amps til it trips at 2.5v/cell but why even stop discharging them at 3.0v why not just run them down to 2.5v all the time for longevity?

have you seen Pajdas test of the 40Q at 5c over 1000cycles from 4.2v to 2.5v
kind of reminds of Okashiras test of the 30Q after 750cycles from 4.2v to 2.5v
they were doing regen every cycle, not every 100 cycles like my test

im really leaning toward these cells like to run hot but not too hot and not too cold

 

[eMark]

So now we know how you were able to achieve a bounce back voltage ranging from +0.31V to +0.43V from April 30th to May 30th without any self-discharge with that 17S4P pack (white, yellow, blue shrink wrap cell labels) with some help from 44-30Q cells :lol:

From May 30th to December 10th only five of those 17s strings had any measurable OCV self-discharge being: 4s, 5s, 17s (loss of only 1mV) and 9s, 13s (loss of 3mV). The other twelve series strings of the 4p groups according to your recorded voltages still had the same "bounce back" voltage (ranging from +31mV to +43mV) from April 30th to December 10th ... that's beyond EXCEPTIONAL. However, now we know your **regenerative** technique was only possible with some help from those 44-30Q cells. What would we do without some help from salvaged 30Q cells :lol:

the vtc6 were holding steady with no discharge at all

From May 30th to December 10th (except for five of the seventeen) thanks to your **regenerative** technique.
Thanks for informing us how you achieved such impressive data.

about a month ago i paralleled 44-30q to them so that all my remaining loose cells were at the same resting voltage

You do realize doing that completely invalidates your two data 17s4p data sheets (April 30th to May 30th) and (May 30 to December 10th). Some would call that fudging the data when you only now tell us you paralled 44-30Q cells to assist what appears to be your impressive **regenerative** technique of returning life by returning lost capacity while reducing the OCV self-discharge of salvaged cells.

the increase in voltage of the 30q's was just bounce back

You wait until now to inform us that you paralleled 44-30Q cells possibly added a few hours before recording the voltages on May 30th. Thus explaining the voltage increase due to "bounce back" voltage from your April 30th to May 30th data. Why didn't you record the actual OCV self-discharge on May 30th before adding the 44-30Q compromise?

Were all of these cells (white, yellow, blue wrap labels) in the 17s4p VTC6 salvaged or new cells ? What about the 44-30Q cells (new or salvaged) you added (paralleled)? Do you realize the following data compromised your **regenerative** technique? Was your plan paralleling those 44-30Q cells as part and parcel of your **regenerative** technique? How did you parallel 44-30Q cells to that 17S4P build? You'd need 34 to make it a 17S6P. Did you mean to say "34"-30Q instead of "44"-30Q ??

 

[goatman]

sorry for the confusion but no, those 44-30q have nothing to do with pack3 or the vtc6. the vtc6 voltages didnt budge while they sat.

i did 3 different packs of 30q-17s4p
2 i use daily and the third has just been sitting since may, all by its lonesome

those 44 are left overs from the 3-30q pack builds
i use them when i need a battery for something,
for example
i needed a 12v battery to trigger the contactor in my car so i could move it, i quickly made a 4s5p of 30q, slapped it in the car and moved it.
then i had 20-30q at a different voltage than the other 24-30q and i had 90-vtc6 at 3.90?
about a month ago i put the vtc6 and 44-30q all together to equalize with each other
heres why
the vtc6 were going into another 17s4p pack, thats 68 cells

that leaves me with 22 vtc6 and 44-30q, which totals 66, i have a couple 30q from when i was testing for a total of 68 cells or another 17s4p pack
so i was going to be building a mixed pack with them
thats why i equalized them recently
but then i needed a backpack battery for my euc so i took 30-30q and built a 15s2p with them
hopefully ive succeeded in confusing you even more :lol:

 

[nicobie]

:lol:

 

[eMark]

i did 3 different packs of 30q-17s4p

Are you certain those 68 cells with white, yellow, and blue label wraps are 30Q cells ...

Those same white, yellow, and blue cell label wraps can be seen in your #3 30q-17s4p pack beside your datasheet ...

How long (2hrs ...1 day) did you allow the bounce back voltages to stabilize in your 17s4p pack after discharging to 2.50V before recording the stabilized resting voltages? That's the only way to determine if and how much OCV self-discharge is still present in those salvaged 30Q cells after 5 days, 10 days and 30 days (April 30th to May 30th) having first stabilized the resting voltages after discharging to 2.50V.

 

[goatman]

100% positive theyre 30q's
i re-wrapped them myself

as far as time for initial reading, probably 1 day or overnight
i just went and looked and it was probably 5 days of sitting

after building then regenerating the pack
all i did was do a discharge to 3.0v to see how many usable ah's there was from 4.1v to 3.0v for the pack and put it to the side and its been sitting ever since then.

 

[eMark]

after building then regenerating the pack all i did was do a discharge to 3.0v to see how many usable ah's there was from 4.1v to 3.0v for the pack and put it to the side and its been sitting ever since then.

You’ve invested much time, energy and expense in this informative thread. Isn't it about time in your regenerative testing to do a 90% SoC to your 17s4p pack (69.70v). 90% SoC is potentially 2700mAh of 30Qs 3000mAh capacity rating.

The mAh discharge capacity of any 18650 cell is figured from 4.20v to cut-off of 3.20v. Thus 90% SoC is a p-group voltage of 4.10v, 80% SoC is p-group voltage at 4.00v, and 70% is p-group voltage of 3.90v.

The average amperage of your resting 17 p-groups is approximately 3.23v or 54.91v for your 17s4p 30Q pack. Charging your 17s4p 30Q pack to 69.70v (4.10v per p-group) is a 90% SoC. What about p-group test voltage of 3.90v (70% SoC). Instead of adjust7ng pack voltage to 3.89v (chart Delta OCV testing voltage) we could just charge to 3.90v (70% SoC -- 2100mAh). Thus shortening the time it takes to do the capacity testing and Delta OCV self-discharge from 3.90V (66.30v) for your 17s4P 30q pack and 39.0v for my 10s3p 30Q pack instead of 90% SoC (17s4p pack at 66.30V). Which do you prefer--charging pack to 90% SoC or 70% SoC? It makes no difference to me as a storage p-group voltage could possibly be as low as 3.50v if self-discharge is of little concern.

4.10v x 17s = 69.70v
3.23v x 17s = 54.91v
69.70V - 54.91v = 14.79v
14.79v / 17 = 0.87v
4.10v - 0.87v = 3.23v

3.90v x 17s = 66.30v
3.23v x 17 = 54.91v
66.30v - 54.91v = 11.39v
11.39v / 17 = 0.67v
3.90v - 0.67v = 3.23v

Will be interesting to see how close to 2700mAh capacity is achieved charging your 17s4p 30Q pack to 69.70v.
... OR ...
How close to 2100mAh capacity is achieved if instead charging your 17s4p 30Q pack to 66.30v.

While your at it why not monitor any Delta OCV self-discharge using what you consider a reasonable resting timeline. I’ll be using the 180 amp DL24P discharge tester to check p-group capacities on my 10S3P 30Q pack. Will track the Delta OCV based on the following chart. Only will use a shorter resting timeline than a "9-day rest period" before recording the Delta OCV self-discharge at 5 days and 10 days ...

What do you consider a reasonable *resting* timeline for our used 30Q packs? What about just 1 or 2 days before recording the Delta OCV self-discharge of the p-groups at 5 days and again at 10 days? Another similar chart says 25 C (77 F) i would just as soon use 68 F (20 C) as that's my winter dry storage temp. I do have small portable heater to put under work bench if you prefer 77 F (25 C) over 68 F when running our tests. I set my thermostat at 68 F during winter and keep one of the bedroom vents closed now that natural gas pricing is thru the roof.

EDIT: There were a few typos that i corrected (typo corrections shown in bold).

 

[goatman]

i checked my charger, its putting out 69.3v, i can open it up and adjust it if its easier for you
the temp in my spare room is sitting around 66f or 19c
whenever youe ready ill charge it up :thumb:

 

[eMark]

i checked my charger, its putting out 69.3v, i can open it up and adjust it if its easier for you
the temp in my spare room is sitting around 66f or 19c
whenever youe ready ill charge it up :thumb:

Being the 68 cells in your 17s4P 30Q pack have hopefully been stabilized / equalized AsMuchAsPossible (since May 30th) a few more days won't hurt before waking up Rip Van Winkle (17s4p) with a bugle charging call :wink:

I'm just about to report the Delta OCV self-discharge (after 10 days) of my 10S3P 30Q pack on my UPDATE thread. Then will discharge the ten p-groups to 2.50v or 3.00v ... whichever works the closest for then equalizing each of the p-groups to 3.228v (your 17s p-group average). So over 1-2 days rest until satisfied the ten p-group average voltage is as close as possible to 3.228v. So, my 10S3P pack won't be ready for charging until Thursday morn at the earliest.

In the meantime between now and Thursday (at the earliest) could you to check/record the Delta OCV self-discharge voltage (mV) of your 30Q 17s p-groups (since May 30th)? Is that even possible if you've had that pack paralleled with what you recently said were "44" additional cells for equalizing the 17s p-groups AMAP?

We need to be on the same page so as to duplicate the parameters of our 30Q test runs (AMAP) for comparing our charge test results for mAh capacity and resulting Delta self-discharge after at least 24 hr rest (instead of 9 days rest) then like that chart example ... https://www.mpdigest.com/wp-content/uploads/2021/08/Figure-4-Charging-impact-on-Delta-OCV-method.png ... measure amount of Delta OCV self-discharge difference after 10 days from that of our recorded p-group resting voltages.

When ready by Thursday morn will be charging my 10S3P 30Q pack at 1.5amp rate. If you'd prefer a 2.0 amp rate that's AOK. Hopefully the dates and even times for our resting timelines and Delta OCV self-discharge timelines will be as close as possible (within a few hours of each other). One variable is that if we use the same charge rate (e.g. 1.5a) does it take longer to charge your 17s4p pack than it does to charge my 10s3p pack ??

Question: Weren't you going to discharge to 42.50v (17s p-groups average voltage--2.50v). In a previous post understood you to say the average 17s p-group discharge was from 4.10v to 3.00v pack voltage from 69.70v to 51.00v (instead of down to 42.50v).

Check on my UPDATE thread the next 2-3 days to get a better idea of the present condition of my 30Q 10s3p pack leading up to our comparative test data on our used 30Q cells. Will post my comparative test data on my UPDATE thread so as to not to derail this thread with my comparable capacity and Delta OCV test run data.

 

[goatman]

regenerating i went to 2.5v

4.1v to 3.0v was just so i had a rough idea of usable ah's.

i can hook an active balancer to the pack to balance it if you want

 

[eMark]

Check PM ... :thumb: :thumb: :thumb:

Should be a GO to begin our comparative 30Q pack tests this Thursday (12/16).

What (if any) is significance of your white, yellow, blue shrink wraps? Did you grade those salvaged 30Q cells and arrange them in any particular order in your 17s4p pack ...

 

[goatman]

bought a multi-color cell wrapper kit from amazon

when salvaging cells from 1 pack ill use the same colors

if i salvage from a different pack ill rewrap with different colors

theres always left overs so if if theres an issue with my blue,yellow, white pack i can grab spares that are blue,whit or yellow

some are black and pink, some are red or silver, easy way to know what cells came from what salvaged pack.

put an active balancer on it
never used one before but its working

 

[eMark]

i dont know the history of the cells other than the packs were considered garbage, unfixable, group voltages all over the map

im looking for a battery that can continuously discharge/charge without suffering lifecycle loss and thats the 30Q

if i salvage from a different pack ill rewrap with different colors

These comparative 30Q tests (17s4p & 10s3p) over the next couple months will be a most interesting learning experience for **regenerating** 30Q cells.

It's possible the present condition of your **regenerative** 30Q 17s4p Pack #3 may outperform my (as of yet) **unregenerative** 30Q 10s3p experimental Vruzend Pack.

Sometime before March (with your help) i'll have attempted to duplicate your **regenerative** procedure with my 30Q 10s3p Pack. The next two months are going to be a most interesting experience.