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

[goatman]

i hear exactly what youre saying

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

the last time i looked the recycle places actually dont recycle them they incinerate them, i think a company in Norway is trying to figure out how to recycle them, i could be wrong

this batch is different than the 70 cells

i dont know if they used Gorilla hot glue but you had to rip the wrapper off to get the cells out and the spot welds were good

i wound up placing the block of batteries in the oven at 110f for about 15 minutes to soften the glue before i could seperate them.

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

 

[goatman]

had some salvaged 30Q-136 that were at 1.96v, desulfated them twice then discharged them with my 30Q-141 test settings
https://endless-sphere.com/forums/viewtopic.php?f=14&t=108547#p1587964

the first discharge was 2462mah

heres the first 7 of the 141 test

#1 d-2519, c-2489 peak temperature 100f
#2 d-2538, c-2488
#3 d-2506, c-2469 peak temp 97f, raising temperature
#4 d-2490, c-2451
#5 d-2478, c-2439
#6 d-2466, c-2429
#7 d-2459, c-2422

heres the desulfated 30Q-136 numbers

discharge curve

ill cycle it for awhile to see what happens
#1 d-2462, c-2422
#2 d-2435, c-2395
#3 d-2417, c-2376
#4 d-2404, c-2368
#5 d-2393, c-2357
#6 d-2398, c-2360
#7 d-2392, c-2354
test had stopped, charged to 4.2v and do another 6 cycles
#8 d-2394, c-2350
#9 d-2385, c-2347
#10 d-2381, c-2344
#11 d-2378, c-2339
#12 d-2375, c-2331
#13 d-2370, c-2328 started another 3 cycles
#14 d-2085, c-2324
#15 d-2364, c-2320
#16 d-2361, c-2319 stopped test to capacity test w/load tester

im trying to desulfate an entire pack right now atleast twice



you can adjust this load tester "on the fly"
ran the 17s pack down to 42.5@2.4 amp discharge

View attachment 17

then lowered it to 1amp discharge to get the "at rest" pack voltage lower, here it is completed



only have a 5amp charger, charged at 1.25amps/cell. not 0.6amps

the pack isnt balanced yet and wanted to see the at rest voltages at Top and Bottom

stopped the charge when 1 of the parallel groups reached 4.20v

if you compare the numbers, bottom balancing should be more accurate



look above at p-groups 15 & 16 they were 4.20v, i burned them down to 4.18 with a light bulb in about 1 minute



theres little magnets tied to the bulb wires, they stick to the dmm probes so you can watch the voltage drop



first full discharge started



capacity test at 3.2v/cell



ar 3.0v/cell



at 2.5v c/o



let battery sit overnight, volts bounced back to around 2.75v, balanced at 2.63v and re tested



capacity is the same as above

3.2v/cell



3.0v/cell



2.5v/cell





lowered the charge to 4.15/cell to top balance the pack
after sitting overnight, pack is sitting balanced at 4.11v/cell which is what i was aiming for

mickey moused the terminal connection for testing til i get other copper



plasti dip



added silicone for "bumpers"



and to back the terminal connection then a coat of plastidip



then plasti-dipped over the silicone

 

[goatman]

trying 25R,
ive put over 10,000kms on these batteries
they were salvaged from a 5p pack that had a max discharge of 6amps/cell and pack died
theyre ran at 10amps max/cell

parallel connect 2-17s4p,



starting voltage



set to 2.4 amp discharge



got 10ah from 2 packs



then i separated the packs, let them sit for 3 hours,
volts bounced back to about 3.0v,
manually balanced the packs

then discharged them separately at 0.51amps to 2.5v/cell





during the testing i lowered my charger to 70.6v so i can bottom balance the pack which should just automatically balance the top

the Marin-25R-4p pack wound up with 8.88ah 4.15v/2.5v



the Scorpion-25R-4p pack was 8.4ah 4.15v/2.5v

 

[goatman]

tested all 3 batteries, my CA3 is not set up properly, i use it to see my volts and km's, the ah and wh/km readings are way off

the xt60's are sparked out and my battery to controller cable is old 14 gauge extension cable. just want to see some numbers to compare them

i just come out the driveway and go full throttle up the hill 0.4kms to a stop sign, take pictures of the ca3 readings then go around the block, down the hill home, take the readings, switch batteries do it again. i think im only using 36amps right now



Marin-25R
start voltage 69.5v
stop sign
.06ah
0.4km
9wh/km
68.1v
volt min 61.5v
a max 6.7
home
end voltage 67.9v-581 ohm
58.8km/h

Scorpion 25R
start voltage 69.9v
stop sign
.06ah
0.4km
68.7v-674 ohm
volt min 63.2
a max 6.5
home
end voltage 68.6v-680 ohm
6.4wh/km
58.9km/h

30Q magnets
start voltage 69.8v
stop sign
.06ah
0.4km
9.6wh/km
dont know the volts
volt min 59.9v
a max 6.88
home
end voltage 69.2v- 685 ohm
7 wh/km
58.3km/h

im surprised the 30Q negative Terminal held up its paper thin (8mm wide and 0.04 thick) and more mickey mouse than the positive , this one



ive got 10/12/14 awg silicone wire and anti spark xt 90s coming this week, to rewire the trike and batteries then program the ca3 properly and turn the phaserunner upto 60 amps for the 0.1mm copper test

 

[goatman]

fixed the CA3 settings, turned phaserunner to 3000 watts/60amps
parallel connected the 30Q and 25R together for 17s8p

Amazon delivered the wire i ordered to another address, be another week for wire and still waiting for 0.1mm copper

went for a ride, starting voltage was 69.9v

end of ride numbers













the 30Q unparalleled





25r unparalleled





took one of the 70 used 30Q's that were left over and did a 10amp discharge from 4.11v to see the sag and it sagged to about 3.58v, i guess i deleted that chart, ill do it again and put it here

3.58x17s=60.86,
my wires and xt60s were warmer than the batteries after the ride

volt sag from previous post w/ca3 not set proper, 9.9v sag

30Q magnets
start voltage 69.8v
stop sign
.06ah
0.4km
9.6wh/km
dont know the volts
volt min 59.9v
a max 6.88
home
end voltage 69.2v- 685 ohm
7 wh/km
58.3km/h

 

[eMark]

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

30Q is an unlikely candidate considering it's a high energy density cell with a shorter life cycle than say a mild-mannered M36 cell capable of 1000 cycles (according to IMR when they carried LG cells). Then if that isn't enuf 30Q has a propensity for a higher rate of self-discharge (e.g. 10-30% of a packs' cells) than any other of it's high energy dense Li-ion 18650 competitors.

Then if that wasn't enough you didn't make your objective any easier by using salvaged 30Q 136 cells (without knowing history) to test out your premise by discharging to 2.5v every 50 cycles as a temporary procedure to possibly extend cycle life over the long haul.

Docware's ageing tests indicated that 30Q had one of the shortest cycle lifes' (to 60% usable capacity) of cells tested and Samsung rates 30Qs usable life at only 250 cycles.

Bottomline: Still maintain it's a QC issue that would be too expensive for Samsung to correct. They can price a 30Q cell at say $4.99 being the highest mass produced and least expensive high energy, high power 18650 cell.

Have your 2.5v discharge capacity tests given you reason to believe that what you hoped would "desulfate" and significantly extend the cycle life of 30Q (40T, VTC6, P42a) shown promise or just a temporary remedy of unknown certainty??

 

[goatman]

okashira went 700 cycles with 7amp discharge to 3.0v and 2.5amps to 2.50v
my 30Q test im already past 250 cycles

okashira
https://endless-sphere.com/forums/viewtopic.php?f=14&t=68556&hilit=okashira+30q&start=100#p1147362

youll see mention of the how the 30Q operates at cooler temperature, (house furnace on, house furnace off)

i need to get an internal resistance tester, i think PWD got this one and liked it
https://www.amazon.ca/Yaootely-Four-Line-High-Precision-Internal-Resistance/dp/B08XYWBCKJ/ref=sr_1_25?crid=PXRHDS6PHA3D&dchild=1&keywords=internal+resistance+meter&qid=1615961957&sprefix=internal+resista%2Ctools%2C244&sr=8-25

i hooked my 150 watt load tester to the 17s4p 30Q pack battery pack was 69.4v turned amps to 2.28 and battery sagged to 68.6v

69.4v-68.6v= 0.8v
0.8v/2.8a=0.3508 ohm

had 26 desulfated 30Q left over made 13s2p with 5mm magnets, pack was 52.6v turned amps to 2 and battery sagged to 52.0v
0.6v/2= 0.30 ohm

ill probably grab another 100 salvaged/used 30Q desulfate them, use the 5mm magnets on another 17s4p and run the packs paralleled where the continuous amp draw will be 4 to 7amps/cell

 

[eMark]

There's a difference between how you interpret "desulfate" (improving/increasing 30Q mAh capacity) and my experimental testing to "de-selfdischarge" cells having a high rate of self discharge.

The reason I was able to pack 3,394mAh into that one cell (3.44v) with the highest self-discharge rate from 1/2/21 to 1/15/21 is because during one of my experiments i drained it nearly empty so as to have a bounce back voltage no greater than 2.51v after a 1 hr rest ... knowing that doing so would ruin the cell's usefulness ... just interested to see how much increased capacity above 3,000mAh. My initial more reasonable discharge to 2.50v and charge to 4.20v resulting in +2,800mAh was because my 30Q "141" cells (10S3P pack) still had considerable storage capacity (TLC) even with 170 cycles in 2020.

What stands out to me is that your "desulfate" discharge to 2.5v results in less than 2,500mAh per p-groups. I interpret that as those salvaged cells have limited use for a typical high power ebike application. What would be the average p-groups mAh capacity if charged to 4.15v and discharged to 3.35V the majority of the time (and only discharged to 2.50v once a month).

What is a possibility from our experiments is that discharging a pack once a month or even bi-monthly to 2.50v can minimize or even eliminate the tendency of high self-discharge among 10% to 30% of a packs 30Q cells.

Because i rarely even drain my 10S3P to the Controller cut-off voltage of 3.25V i'm considering discharging my Vruzend 10S3P pack to 2.50V at least once a month (or bi-monthly) if necessary ... with the purpose being that come July/August after 100 more cycles that none of the 30 cells (21 "141" / 9 "KH1T") will suffer from a high rate of self-discharge.

What is a reasonably priced commercially available discharger with variable amperage discharge (e.g. 1.25-2 amps) for a 10S3P pack. Beause i'm retired with time on my hands it's not necessary to discharge over a 3 amp rate.

 

[goatman]

desulfate doesnt fix the resistance, these cells sag quite abit
the capacity ive shown up above at different voltages, too many pictures i guess
17s4p of 30Q
at 3.2v/cell the capacity is 9.81ah or 2452mah/cell
at 3.0v/cell the capacity is 10.77ah
at 2.5v/cell the capacity is 11.71ah

this guys setup with a lvc would be perfect for your packs, i think the lvc is good to 36v? he has links to Amazon for about $50

https://youtu.be/toDM8_fDx_w?t=74

but you might need a new mosfet like mine did

https://endless-sphere.com/forums/viewtopic.php?f=14&t=110773

 

[eMark]

https://endless-sphere.com/forums/viewtopic.php?f=14&t=110773

Thanks for the youtube link.

It's probably more machine than i need, but am not interested in fabricating my own 38V discharger. Really doesn't need to be more than 38.0V discharge to 30.0V with variable control from 1.00 amp to no greater than 2.50 amp for my 10S3P experimental pack.

That's assuming a pack discharge once or twice a month to 30V would diminish/eliminate a "high" rate of self-discharge (like that 3.44V cell). Being that the 141 cells were shipped/recd at 3.40V and the "KH1T" at 3.46V maybe just discharging to 3.33V is the magic number, IF in fact it would help diminish a high rate of self-discharge. Like i expressed in my UPDATE thread a "leaking" 30Qs voltage does not affect the cells ability to still store the same capacity of a 30Q cell that doesn't "leak" ... at least that was my preliminary finding.

Am coming to the conclusion that discharging to 2.50V is too low (shortens cycle life). Am thinking now no lower than 3.00V, and need to do more testing of the other seven 30Q cells suffering from high self-discharge. Currently running some tests on those three cells at 3.70V (least amount of self-discharge) with different discharge voltages to see affect of degree of any future self-discharge. Just finish yesterday and resting them for five days before checking if resting voltages of all three are still at 3.75V. Will post results on my UPDATE thread Monday.

 

[goatman]

got a 16s6p of 30Q-136, another salvage pack, glued together and spot welded,

badly out of balance but no dead p-groups
going to bottom balance to 2.5v then charge to 4.15v two times and see what happens

you can see under the 13s 4.09 the pack was made March.25,2014



1 layer of nickel






used my 70.2v charger to charge the 16s pack to 66.4v/4.15v
waited 1hr and cells settled at 4.08v

found a screen that shows resistance as you discharge



16.6ah capacity from 4.08v to 2.5v is pretty good



charged the pack and unplugged the charger at 67v/4.187v
after 2hrs pack was sitting balanced at 65.7v/4.10v

if i ran 16s packs id probably just start using it

draining it down to 56v/3.5v to tear the pack down to individual cells to sort out

 

[goatman]

tore down the pack
ground off the spot welds re-wrapped the cells and equalized them with each other for 24 hrs



took the voltage readings afterwards

76@ 3.323v
3@ 3.323/4v
8@ 3.324v
8@3.325v
1@3.326



ill let them sit for awhile and see what happens

made a 17s4p pack



charged to 70.2v(4.13v) but the load tester is showing 69.8v
ill try to calibrate it later
going to check to make sure the pack is balanced by desulfating twice and put it to use



3.2v



3.0v



2.5v



let the pack sit overnight after charging
it settle at 69.8v (4.10/4.11)
discharged to 51v (3.0) 10.75ah
the other 30Q pack was 10.77ah

 

[eMark]

got a 16s6p of 30Q-136, another salvage pack, glued together and spot welded, badly out of balance but no dead p-groups

used my 70.2v charger to charge the 16s pack to 66.4v/4.15v
waited 1hr and cells settled at 4.08v

16.6ah capacity from 4.08v to 2.5v is pretty good

charged the pack and unplugged the charger at 67v/4.187v
after 2hrs pack was sitting balanced at 65.7v/4.10v

draining it down to 56v/3.5v to tear the pack down to individual cells to sort out

Over the last 18 days (since March 25, 2021) could you give us some idea out of the 96 cells (16s6p) how many suffer from a high rate of self-discharge (e.g. self-discharge from 3.50v to 3.35v or lower over the past 18 days) ?

Out of the two salvaged packs have you determined the number (%) of cells you'd consider suffer from high self-discharge ? Have you tested the cells in the other salvaged pack to determine the number that do not suffer from high self-discharge ?

Like me have you come to the conclusion that draining the cells to 2.5v does not "desulfate" (restore lost capacity), but in fact most likely does more harm than good to their remaining usefulness (cycle life) ?

Out of curiosity what project might these two salvaged packs of questionable 30Q (2014) cells still have some usefulness assuming a significant number of sorted cells do not suffer from high self-discharge ?

 

[goatman]

the 96 cells
3 are still self discharging
68 i built a pack, 17s4p

the remaining 25 cells i equalized with 23 left overs from the first build



42 of those have been sitting at 3.71v for a week
the 6 off to one side are sitting at 3.70v

the black wrapped cells i did my own resistance test on, i dont have a tester, its not accurate, i was using about 5 feet of wire

i hit them with a 5amp discharge and took 3 readings
initial volt sag
voltage at 10 seconds
voltage at 20 seconds



do the math



very first pack i built ive got about 500 miles on, no problems

second pack i was waiting for 0.1mm copper to finish the terminal connections but just found out Amazon lost it in shipping, im not going to wait another 6 weeks for copper, ill just mickey mouse the connections and put it to use for now

my battery guy has another dead 30Q pack i need to go grab
i should be able to build 2 more 30q packs from that and my left overs

he also has a dead vtc6 pack im going to grab

then ill have enough batteries to get me started on my boat conversion

ill just keep doing a pack a month

 

[goatman]

Like me have you come to the conclusion that draining the cells to 2.5v does not "desulfate" (restore lost capacity), but in fact most likely does more harm than good to their remaining usefulness (cycle life) ?

no i disagree

im going to "desulfate" these packs every 100 cycles or 3 months whichever comes first

look at the 40T test, it got capacity tested/desulfated every 100 or 150 cycles
500 cycles into the test and its doing just fine
the 30Q test same thing

i just think you need to do some pack maintenance
these cells , the damage is already done but i think theyre save able

 

[eMark]

got a 16s6p of 30Q-136, another salvage pack, glued together and spot welded,

badly out of balance but no dead p-groups
going to bottom balance to 2.5v then charge to 4.15v two times and see what happens

used my 70.2v charger to charge the 16s pack to 66.4v/4.15v
waited 1hr and cells settled at 4.08v

Isn't a self-discharge in 1hr from 4.15v to 4.08v a high rate of self-discharge ? Explain

16.6ah capacity from 4.08v to 2.5v is pretty good

Agreed, as more mAh between 2.5v to 3.5v, but who (what research study) has ever concluded that draining their pack to 2.5v every 100 cycles will prolong cycle life ? Doesn't conventional logic suggest that to do so would do more harm than good when it comes to prolonging a packs' cycle life ?

charged the pack and unplugged the charger at 67v/4.187v
after 2hrs pack was sitting balanced at 65.7v/4.10v

How do explain a self-discharge from 4.187v to 4.10v in just 2hrs ? I've never seen any time that high degree of self-discharge in my 10S3P 30Q pack when charging to 4.10v at 1.5 amp. Voltage still remains at 4.10v.

 

[goatman]

goatman wrote: ↑Mar 25 2021 9:08pm
got a 16s6p of 30Q-136, another salvage pack, glued together and spot welded,

badly out of balance but no dead p-groups
going to bottom balance to 2.5v then charge to 4.15v two times and see what happens

used my 70.2v charger to charge the 16s pack to 66.4v/4.15v
waited 1hr and cells settled at 4.08v
Isn't a self-discharge in 1hr from 4.15v to 4.08v a high rate of self-discharge ? Explain

no, it will just sit at 4.08v, ill explain below

goatman wrote: ↑Mar 25 2021 9:08pm
16.6ah capacity from 4.08v to 2.5v is pretty good
Agreed, as more mAh between 2.5v to 3.5v, but who (what research study) has ever concluded that draining their pack to 2.5v every 100 cycles will prolong cycle life ? Doesn't conventional logic suggest that to do so would do more harm than good when it comes to prolonging a packs' cycle life ?

you can see it my 30q/40t test results

if a battery loses 1mah/cycle, it should show it in the cycle testing
heres 40T
https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550#p1567975
4.2v-2.5v capacity test is done after 375 cycles, 3818mah. 90% of initial 4216mah

it lost 398mah in 375 cycles from 4.2v to 2.5v

first test discharge was 3180 mah
after 515 cycles, 2977 mah
it lost 203 mah from 4.2v to 3.2v

#509 d-2980, c-2925
#510 d-2980, c-2924
#511 d-2979, c-2923
#512 d-2977, c-2923
#513 d-2978, c-2924
#514 d-2977, c-2923
#515 d-2977, continuous operation doesnt seem to affect its life cycle
test done, put battery on shelf

so its like desulfating brings capacity from the 3.2v to 2.5v area of the battery and brings back up into the 4.2v to 3.2v area
you can see the before and after results
i posted how the mah gets redistributed in the vtc6 thread
look at steps 1 through 5 in the before and after picture

https://endless-sphere.com/forums/viewtopic.php?f=14&t=108661#p1605950


goatman wrote: ↑Mar 25 2021 9:08pm
charged the pack and unplugged the charger at 67v/4.187v
after 2hrs pack was sitting balanced at 65.7v/4.10v
How do explain a self-discharge from 4.187v to 4.10v in just 2hrs ? I've never seen any time that high degree of self-discharge in my 10S3P 30Q pack when charging to 4.10v at 1.5 amp. Voltage still remains at 4.10v.

its what batteries do, in my tests i charge to 4.2v with 0.10 c/o and within 2 minutes the voltage will drop to 4.191v, after 24hrs it will be 4.16v and just stay there, heres a comment from the 40T test

#485 d-3038, c-2985
#486 d-3034, c-2981
#487 d-3030, c-2977
test had stopped, charged and restarted
#488 d-3046, c-2963 giving a 24hr break to use tester on another battery
battery was 4.16v charged to 4.2v
#489 d-3034, c-2947
#49

i dont use a bms on any of my packs, theyre all salvaged cells that were bottom balanced and thats just how its always been for me. if i want my cells at 4.10v, ill charge to 4.15v but they always settle around 4.10v

even during cycle testing of the 30Q and 40T by the time you cycled the battery 100x, the 2 minute wait time inbetween charge and discharge, the battery voltage will drop from the initial 4.191v to 4.185v, desulfate and its back to 4.191v

 

[eMark]

i dont use a bms on any of my packs, theyre all salvaged cells that were bottom balanced and thats just how its always been for me. if i want my cells at 4.10v, ill charge to 4.15v but they always settle around 4.10v

Isn't that bounce back voltage because of CVCC ... and possibly a charge rate higher than 1.5 amps ? What charge rate do you use on your salvaged 16s6p pack of "desulfated" 30Q cells ?

even during cycle testing of the 30Q and 40T by the time you cycled the battery 100x, the 2 minute wait time inbetween charge and discharge, the battery voltage will drop from the initial 4.191v to 4.185v, desulfate and its back to 4.191v

You've yet to "desulfate" your 16s6p pack every 100 cycles or 3 months to see if in fact your procedure mitigates unacceptable 30Q self-discharge. Testing your "desulfating" procedure on one salvaged 30Q cell may also prove itself helpful in extending the cycle life of your 16s6p 30Q pack of salvaged cells ... best of success :thumb:

i just think you need to do some pack maintenance

If you've followed some of my other posts and 30Q UPDATE thread you'd have to agree that i'm a stickler for pack maintenance to extent cycle longevity. Like you i don't use a BMS, bottom balance the p-groups, then bulk charge 10S3P pack at 0.5C to 41.0v with p-groups within 9 to 12 mV (before discharge), average discharge is around 3.5V (before bounce back), also replaced 9 30Q cells suffering from unacceptable self-discharge.

If that isn't enuf my etriking is mild-mannered (far from raw performance). The only way i can interpret your above underlined comment (in red) is by adhering to what you refer to as a "desulfating" procedure that you apparently now believe is essential to 30Q pack maintenance and its cycle life longevity ...

going to bottom balance to 2.5v then charge to 4.15v two times and see what happens

Other than a "desulfating" procedure that you apparently belief is beneficial to "pack maintenance" what have i ever posted that has led you to believe my pack maintenance is sub-par and now sub-par in need of "desulfating" every 100 cycles or every three months ?

Still think you need to come up with a more appropriate term than "desulfate" to give your lithium ion procedure more credibility ... assuming that your procedure does in fact improve/increase cycle longevity by mitigating 30Q self-discharge ... time will tell :thumb:

 

[goatman]

If you've followed some of my other posts and 30Q UPDATE thread you'd have to agree that i'm a stickler for pack maintenance to extent cycle longevity. Like you i don't use a BMS, bottom balance the p-groups, then bulk charge 10S3P pack at 0.5C to 41.0v with p-groups within 9 to 12 mV (before discharge), average discharge is around 3.5V (before bounce back), also replaced 9 30Q cells suffering from unacceptable self-discharge.

If that isn't enuf my etriking is mild-mannered (far from raw performance). The only way i can interpret your above underlined comment (in red) is by adhering to what you refer to as a "desulfating" procedure that you apparently believe is essential to pack maintenance and cycle life longevity ...

not all batteries, some self heal
look at data sheets for the amps and temps that cell can give 100% capacity
alot is what most say,
the lower the C-rate the longer the lifecycle

look at docs test where he babies a 30Q without desulfating it



look at Pajda hitting it with 15amps full discharge to 2.5v



hg2 does really well, like a 25r does really well
look at anodes and cathodes



what you dont see in all that testing, is the self healing bumps in capacity like the Tesla cell shows



1- reason why, pajda and okashira were doing full discharges(i didnt look to see if they were losing 1 mah/cycle)
2- doc didnt desulfate( how many mah/cycle did he lose, 0.5 mah/cycle?)

i never did a capacity chart but if i did,( every 100 cycles) it would look like the self healing of the Tesla cell after a 30hr break

Other than a "desulfating" procedure that you belief is essential to "pack maintenance" what have i ever posted that has led you to believe my pack maintenance is sub-par and in need of "desulfating" every 100 cycles or every three months ?

Still think you need to come up with a more appropriate term than "desulfate" to give your procedure more credibility assuming that your procedure does in fact improve/increase cycle longevity ... time will tell :thumb:

not running your batteries at 100%a and 100%t
what i mean is
if you ran your batteries at 10amps or 0.6amps discharge, thats 100%a
then 25c to 40c is 100%t, whats that 75f to 102f?

 

[eMark]

got a 16s6p of 30Q-136, another salvage pack, glued together and spot welded, badly out of balance but no dead p-groups

going to bottom balance to 2.5v then charge to 4.15v two times and see what happens
you can see under the 13s 4.09 the pack was made March.25,2014

used my 70.2v charger to charge the 16s pack to 66.4v/4.15v
waited 1hr and cells settled at 4.08v

16.6ah capacity from 4.08v to 2.5v is pretty good

charged the pack and unplugged the charger at 67v/4.187v
after 2hrs pack was sitting balanced at 65.7v/4.10v

draining it down to 56v/3.5v to tear the pack down to individual cells to sort out

Why did you decide to drain as low as 3.5V cell instead of balancing each p-group to 3.75V ? Was expecting you to let the individual cells rest for at least five days before checking the voltages to see how many suffered from self-discharge and how many were still at 3.75V ? Why did you think it not necessary to determine the extent of self-discharge ? Would've expected to see more than a few 30Q 136 cells in a 2014 pack experiencing self-discharge.

My discharge/drain and balance of each p-group to 3.75V in my 30Q UPDATE thread was to simulate a winter storage scenario. Then i disassembled the 10S3P pack to test individual cell voltages (after 2hr rest) resulting in all thirty cells between 3.75V-3.74V on 1.2.21. Then checked again on 1.5.21 with 9 cells showing self-discharge and again on 1.15.21 with ten cells suffering from self-discharge (see bottom photo).

On my 30Q UPDATE thread the cell with the highest self-discharge rate was at 3.44V after 15 days and the lowest self-discharge rate at 3.73V after 15 days. These ten cells continued on their self-discharge journey. Twenty of the 10S3P 30Q 141 cells were still holding at 3.75V-3.74V after 44 days :thumb:

I was expecting (hoping) you would do a similar test to determine the number of cells suffering from self-discharge after at least five days and the variance from the highest rate to the lowest. Being there was no hurry to finish your pack thought you might even see how many cells didn't show any self-discharge after 15 days.

Why did you decide not to do a 5-day test the individual cells of the "16s6p of 30Q-136, another salvage pack" for self-discharge and drain the pack as low as "56v/3.5v" in order to sort cells ?
________________________

Would you explain how you bottom balance your 14S and 16S p-groups ? Am attaching photos of ways i've experimented with bottom balancing p-groups with variance as tight as 4mV between p-group voltages with final top p-group variance between 9mV-12mV at 4.10V after bulk charging.

The FIRST photo isn't practical as no two iDST BattGO BG-8S will read the same voltage and can't be calibrated to do so. However, they can balance the p-groups within 10-15mV which is close enough. Using two 8S JST-HT balance leads you don't need provision for splitting a 16S pack into two 8S packs in order to bottom balance the p-groups. See blue connection in middle back indicating pack is in 10S3P mode.

The SECOND photo is using one iDST BattGO BG-8S with a split provision for a 10S, 12S, 14S or 16S pack using two 5S, 6S, 7S or 8S JST-HT balance leads.

The THIRD & FOURTH photo takes less time than the slow resistance discharge BattGO BG-8S) and can be as accurate as you have the will and time. This is how i balance the p-groups of my experimental Vruzend 10S3P 30Q 141/KH1T pack.

The FIFTH photo is the self-discharge chart after fourteen days from 1.2.21 to 1.15.21. Was hoping you might report the number of cells with self-discharge, variance of cells with self-discharge and number of cells having no self-discharge after at least five days, if not after 14 days. Maybe, if you were retired like me you would have had the time, sooo being you're not 77 years young i understand 8)

 

[goatman]

Why did you decide to drain as low as 3.5V cell instead of balancing each p-group to 3.75V ? Was expecting you to let the individual cells rest for at least five days before checking the voltages to see how many suffered from self-discharge and how many were still at 3.75V ? Why did you think it not necessary to determine the extent of self-discharge ? Would've expected to see more than a few 30Q 136 cells in a 2014 pack experiencing self-discharge.

if im building a pack or taking it apart, i like doing it with lower voltage
once apart i made 2-48 cell groups and equalized them for i think 24hrs then took the foil off let them sit for a day
took 34 cells from each block of 48 that were the same voltage and made a pack
i think the pack was built and done by april.01- 2 weeks ago
theres no self discharging

I was expecting (hoping) you would do a similar test to determine the number of cells suffering from self-discharge after at least five days and the variance from the highest rate to the lowest. Being there was no hurry to finish your pack thought you might even see how many cells didn't show any self-discharge after 15 days.

i can do that, i think theres 25 posts to a page, i might just do a couple bump posts to get to page 3 so its not such a looooooooooooong scroll to get to see whats being said

 

[goatman]

Would you explain how you bottom balance your 14S and 16S p-groups ? Am attaching photos of ways i've experimented with bottom balancing p-groups with variance as tight as 4mV between p-group voltages with final top p-group variance between 9mV-12mV at 4.10V after bulk charging.

i just use a 12v light bulb with a couple magnets on the wires and click it on the p-groups i want to take down

if the pgroup voltages are around 2.8v, i might burn off 4-pgroups at once, thats only 11.2v for a 12v bulb

 

[goatman]

42 of those have been sitting at 3.71v for a week
the 6 off to one side are sitting at 3.70v

i also have atleast 9 other cells that are garbage

 

[goatman]

bump

 

[goatman]

bump