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

goatman

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checking to see if any battery experts can tell me what is happening with these batteries. i dont know the word for it to do a google search.

if i do a capacity test on 30Q or 40T

ill get a curve like this

xtOI79D.png


if i repeat the test a couple times the curve smooths out

jL3EqsC.png


and step 1-4 will jump from 183mah to over 300 mah

fLcuXPY.jpg


you can see the testing here

https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550&start=25#p1604360
 
yes sulfation is a lead thing, thats why i put it "desulfate" and asked if anyone knows what this is

kind of click-baity

rg12 has 40T batteries and the same tester i have, be nice if he could verify what im seeing
 
its good to see the same profile but im wondering why, while testing i can increase the mah by doing a capacity test

its like the deep discharge to 2.5v brings mah back into the cell for a dozen or so cycles
thats why i used "desulphate" but lithium gets dendrites? not a clue

it takes 2 capacity tests to straighten out the discharge curve

heres the 30q before capacity at #100-2395mah, it took 56cycles to reach 2395 discharge mah

#100 d-2395, c-2355
0.6amp capacity test, #1-3170mah, #100- 3092mah. 78 mah loss
#101 d-2542, c-2501 i dont know whats happened with these numbers, im going to shut down and restart in the morning
#102 d-2528, c-2486
#103 d-2517, c-2472
#104 d-2501, c-2456
#105 d-2489, c-2445
#106 d-2479, c-2435
#107 d-2470, c-2427 shutdown and restart
#108 d-2463, c-2421
#109 d-2458, c-2416
#110 d-2455, c-2413
#111 d-2450, c-2408
#112 d-2446, c-2405
#113 d-2442, c-2401
#114 d-2440, c-2398
#115 d-2438, c-2396
#116 d-2436, c-2393
#117 d-2432, c-2391
#118 d-2431, c-2388
#119 d-2429, c-2386
#120 d-2427, c-2387
#121 d-2428, c-2384
#122 d-2424, c-2384
#123 d-2426, c-2385
#124 d-2425, c-2382
#125 d-2423, c-2382
#126 d-2421, c-2380
#127 d-2420, c-2377
#128 d-2417, c-2376
#129 d-2416, c-2373
#130 d-2413, c-2370
#131 d-2413, c- usb cable was pulled from computer at 2100 mah, gave it a charge top up
#132 d-2418, c-2371
#133 d-2414, c-2373
#134 d-2411, c-2370
#135 d-2410, c-2367
#136 d-2407, c-2366
#137 d-2408, c-2366
#138 d-2406, c-2364
#139 d-2405, c-2364
#140 d-2405, c-2362
#141 d-2406, c-2365
#142 d-2405, c-2363
#143 d-2404, c-2364
#144 d-2404, c-2363
#145 d-2404, c-2362
#146 d-2401, c-2361
#147 d-2400. c-2359
#148 d-2400, c-2357
#149 d-2399, c-2358
#150 d-2399, c-2359
#151 d-2398, c-2355
#152 d-2397, c-2355
#153 d-2396, c-2355
#154 d-2396, c-2354
#155 d-2393, c-2352
#156 d-2395, c-2353
#157 d-2395, c-2352
#158 d
 
under 10/7.5/5/2.5 amp discharge, its the 30Q im showing there. it gained 147mah from #100 to #101 because of the capacity test

if you go to #200 of the 30q test it happens again

#199 d-2371, c-2330
#200 d-2372, c-2329
#200 d-3026, c-2863 capacity test
#201 d-2497, c-2453

im just going to keep cycling the 30Q and do the 0.6amp discharge capacity test every 50 cycles to see what happens
 
What temperature are you running these tests at? because temperature will influence the internal resistance a lot.

If comparing to cell spec sheets, you need to be at ~70F.
 
capacity tests are done at room temp/75f

while doing the life cycle testing with the 10/7.5/5/2.5 amp discharge testing

10amp reaches 97f
7.5amp 102f
5amp will stay at 102f
end of 2.5amp will be 90f
start of charge will be 89f
end of charge will be 75f
next cycle starts at 75f

temperatures will be the same discharge temp at #100 and #101 but the mah increased 147mah because the 0.6amp discharge happened inbetween the cycles
 
Don't you love high capacity cylindrical cells and how they over promise and under deliver on discharge efficiency...
..there's a reason why the voltage curves and max capacity graphs are generated at 0.000001 amp.. :lol:
 
i thought it was doing really good, the cycle testing is 4.2v to 3.2v :D

the capacity test is 4.2v to 2.5v

im just wondering if every 50 cycles you should do a 0.6 amp discharge to 2.5v to double the lifecycle of 30q and 40T
 
Cycle life testing,..no matter how well thought out and conducted,.. can never replicate “real world” applications.
... Discharges are rarely continuous, mostly at uneven rates, to random end voltages.
...And charging, whilst often continuous and at steady known rates, is rarely from the same initial voltage start point.
... Rest time between cycles is also very different and variable.
I suspect all this would result in very different “real life” actual life span outcomes.
But controlled tests, such as yours , is the only practical way of assessing and comparing cell performance before putting them into service.
 
goatman said:
every 50 cycles you should do a 0.6 amp discharge to 2.5v to double the lifecycle of 30q and 40T

Sounds like something from a different chemistry family
 
I'm feeling more certain the increased performance from subsequent test runs is tge result of increased internal temperatures.

You could test that by letting them settle an hour before each run,

ideally pre-warming cells to say 30°C every time (whatever so long as well above ambient)

bet that will show greater consistency
 
temps are the same as always, if there is a difference it recovers in 2 or 3 cycles
this was the fridge test

charged battery placed in fridge for 18 hrs at 5 celsius and restart the test
#213 d-2366, c-2332
#214 d-2374, c-2332
#215 d-2376, c-2334
doing 0.6amp discharge capacity test to see if lost mah can be recovered
#216 d-3042, c-2867 capacity test


ill show the test im doing right now and 2 pictures

first picture is cycle 225
second picture is cycle 234 and youll see the mah change at 1-1 and 10-1
at cycle 250 ill do the capacity test, resume testing and the mah will be brought back up

BwB7IFh.png


vBzGQ3y.jpg


BRspDLz.jpg
 
The **internal** temperature is what matters, not the outside.

Why are you cooling the cells down?

25°C / 77°F is the standard for controlled testing.

Hotter is better in actual usage for performance and longevity.

Cooler is good only for storage longevity, with no cycling.
 
im not cooling down the cells, they do it on their own

i set discharge voltage cut off by temp so the battery doesnt exceed 104f/40celsius during the discharge test, if i go hotter like 105f it will lose more mah/cycle than 104f or less.

i used to think a fatter battery like a 21700 or 26650 would trap the heat inside it but they dont, they run cooler than a 18650 at 10 or 7.5 amp discharge

when i saw Tesla switch to a fat cell i figured heat was part of the reason they went fatter.

a 40T can put out 2370 mah before reaching 102f

jjzMPqk.jpg


a 30Q can put out about 1170mah before reaching 102f

vBzGQ3y.jpg


the mnke 26650 can be discharged at 7amps putting out about 4200mah? (cant remember) without ever reaching 102f f

i couldnt set discharge cut offs for cycling by temperature like i do other cells, its runs too cool
https://endless-sphere.com/forums/viewtopic.php?f=14&t=107191#p1569263
 
john61ct said:
goatman said:
every 50 cycles you should do a 0.6 amp discharge to 2.5v to double the lifecycle of 30q and 40T

Sounds like something from a different chemistry family

went googling and came across an article on the SEI layer

https://circuitdigest.com/article/what-is-solid-electrolyte-interface-sei-to-improve-lithium-ion-battery-performance

i also went looking for an exchange between docware and another es member about endothermal and exothermal but havent found what im looking for yet, here it is

https://endless-sphere.com/forums/viewtopic.php?f=14&t=102891&p=1505696&hilit=endothermic#p1505590

heres Pajda trying to find the new 141 30q for testing

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=225#p1525408

has pajda tested them yet?
 
had a power outage while doing the capacity test, the test was stopped at about 3.6v and then resumed 2 hours later when the power came back on, that interruption caused the capacity test to fail to provide the capacity or straighten the curve

here it is to 3.6v

mvCmYh6.png


and resumed

Jy6gPpE.png


so i did it again

OdWRYhi.png


heres a picture of cycle #242 before the capacity test, look at steps 18-1, 18-2,18-3, 18-4 and then compare to cycle #243 after the capacity test and youll see how the mah gets redistributed in the second picture, 1-1, 1-2, 1-3, 1-4

#242
7rApChs.jpg


#243
NMORCAw.jpg
 
Desulfate samgsung 40t cells in brick bunker 100ft from all building and tree's find the 220 outlet and make sure POS and Ned is right and give it the juice.
Will guarantee No more worries of desulfation ever again. Oh stand back 100ft. Behind blast sheilds.
 
going to desulfate some salvaged 30Q from bad packs

these were in a hot glue pack

5 cells at 1.97v 1s5p

IMG_20210223_081939.jpg

charged to 4.2v at 3amps

then discharged to 2.5v at 3amps (0.6amps) curve looks fine

GNGl4YU.png


charged to 4.2v at 3 amps

OWbhULp.png


then i discharged them a little bit and theyre sitting at 4.02v . now just put them on the shelf and see what happens

had another 20 that were 3.28v to 3.03v, taped them together to equalise

IMG_20210224_155200.jpg

theyre sitting at 3.22v right now, in a couple days ill make a 2s10p pack and desulfate at 5amps
 
goatman said:
going to desulfate some salvaged 30Q from bad packs

5 cells at 1.97v 1s5p

charged to 4.2v at 3amps

then discharged to 2.5v at 3amps (0.6amps) curve looks fine

charged to 4.2v at 3 amps

then i discharged them a little bit and theyre sitting at 4.02v . now just put them on the shelf and see what happens

had another 20 that were 3.28v to 3.03v, taped them together to equalise

theyre sitting at 3.22v right now, in a couple days ill make a 2s10p pack and desulfate at 5amps
Had you previously determined if all these 25 cells ("5 cells at 1.97v 1s5p" and "20 that were 3.28v to 3.03v") were suffering from moderate to high self-discharge?

When you say they (all 25 cells) need "desulfating" you imply that they all suffer from an unacceptable degree of self-discharge. Do you know for a fact that all 25 cells suffered from unacceptable self-discharge? For all you know maybe 15, or only 8 out of 25 suffered from unacceptable self-discharge.

You first need to determine how many suffer from unacceptable self-discharge and only then perform your "desulfate" routine on just those cells suffering from unacceptable self-discharge to see if a partial "fix" is in and for how long ... experimental research parameter :wink:
 
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