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

[goatman]

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

and out of that 96 cell pack
6 are bad they self discharged to around 3.50v to 3.60v from 3.71v in 2 weeks

the other leftovers
39@ 3.702v
1-3.698
2-3.695
1-3.687
2-3.681
1-3.666
1-3.658
1-3.653

 

[nicobie]

I just noticed this thread. I didn't know you were doing this. Nice job!

As fechter says in his signature here:

"one test is worth one thousand opinions"

 

[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

Just to clarify "S-group 10" is referring to the 4p-group (at 3.186v) at S10 location on the 17s4p pack and "S-group 6" is referring to the 4p-group (at 3.184v) at S6 location on the 17s4p pack.

Should've included an additional photo (with previous post) taking the voltage reading at 3S location on the split 5S3P JST female connector. I check voltage readings and equalize p-group voltages AsCloseAsPossible on all 10S locations of the two split 5S3P packs in order to bottom balance the ten p-groups ACAP before bulk charging. This has become my preferred method of bottom balancing the p-groups before bulk charging via the two paralleled 5S3P packs of my experimental 10S3P 30Q 141 DIY build.

The bottom photo is my salvaged headlight bulbs for discharging the 30Q 141 cells to 2.5v (or lower) in an attempt to lessen or mitigate unacceptable self-discharge which seems to be more of a problem with 30Q high energy dense cells.

 

[goatman]

Just to clarify "S-group 10" is referring to the 4p-group (at 3.186v) at S10 location on the 17s4p pack and "S-group 6" is referring to the 4p-group (at 3.184v) at S6 location on the 17s4p pack.

yes

 

[eMark]

Just to clarify "S-group 10" is referring to the 4p-group (at 3.186v) at S10 location on the 17s4p pack and "S-group 6" is referring to the 4p-group (at 3.184v) at S6 location on the 17s4p pack.

yes

I've come to the conclusion that out of the nine 30Qs with self-discharge that maybe only a few needed to be replaced in March instead of ten out of the thirty cells (10S3P) with self-discharge. The one cell for sure was the one with the highest self-discharge from 3.75v to 3.44v after 14 days (1.2.21 to 1.15.21). I now say this because self-discharge (IMO) isn't a problem when you recharge your pack every day or every other day plus bottom balancing and top balancing within 4mv with the BattGO BG-8S, IF that's even necessary as a cheap BMS hopefully balances p-groups at best within 25-30mv.

Self-discharge is more of a problem during longer layovers between discharge and next charge (e.g. winter storage). Because 30Qs are more prone to self-discharge we both have learned the value of bottom balancing the 30Q p-groups as close as possible before bulk charging. I use to use a combination of resistance discharge and 1S charge for bottom balancing (see previous photos). Now i just use my HTRC C240 balance charger set at 1S when charging whatever p-group(s) that need it to balance them as close as possible before bulk chargin. If i've nothing better to do i may infrequently top balance the p-groups with the BattGO BG-8S as close as 4mv IF it's a rainy day.

I see that IMR is now charging $6.50 for 30Q cells. Even if ordering 100 cells you previously could purchase 100 for about $4.35 each. Makes one wonder if Samsung has finally figured out the 30Q self-discharge problem and now providing IMR with improved 30Q cells (thus the increase in price ?).

 

[john61ct]

that's a stretch

higher pricing does not imply better quality

usually just higher demand or tighter supply

99.9% of prospects still see 30Q as a good battery.

If the maker thought the problem worth fixing they likely would have done so a ling time ago

A more profitable and IMO likely strategy would just be to release a new-named model with lots of improvements and just eventually discontinue the old one

 

[goatman]

i agree, self discharging batteries that sit too long unused will get too far out of balance for a cheap bms to fix
personally i dont like top balancing
i want my batteries to hit 3.0v or my lvc, all at the same time

by lowering the charge of my bottom balanced pack to 4.15v from 4.2v my pack will stay balanced
if it doesnt, i lower it to 4.10v and then it does
as the pack gets older i may need to lower it again

if the battery no longer has the capacity to stay balanced, im overcharging it

if i need to leave a battery charging for days to try and top balance it, thats plain moronic in my opinion and probably kills weak battery packs faster than anything else

actually i should say, top balancing older packs to 4.2v is plain moronic

and only balance at one point, top, bottom or your lvc

balancing at both top and bottom is a defeating

 

[john61ct]

if i need to leave a battery charging for days to try and top balance it, thats plain moronic in my opinion and probably kills weak battery packs faster than anything else

actually i should say, top balancing older packs to 4.2v is plain moronic

and only balance at one point, top, bottom or your lvc

Preach!

Anyone balancing at more than one voltage point is just revealing they don't understand what balancing is for, how it works at the most fundamental level.

Some dedicated balancing gear vendors (non- protective BMS) claim you can just leave the balancing going 24*7 while in use

in theory maybe, IRL just no

That cutesie youtuber shill fell for that idea and then acted all disappointed when he didn't get the **overall capacity** boost he'd expected!!

https://youtu.be/_NYFq7ZJg4c

 

[eMark]

i agree, self discharging batteries that sit too long unused will get too far out of balance for a cheap bms to fix
personally i dont like top balancing
i want my batteries to hit 3.0v or my lvc, all at the same time

Agree with all you said ... preach it bro. My Vruzend 10S3P 30Q is an experimental pack being easy to assemble, disassemble and reassemble. Being retired i've the time to experiment, experiment, experiment which is beneficial along the learning curve.

By the way it sounds like foghorn "I say, I say, I say" is back in his rare form :wink:
Maybe those 30Q "KH1T" cells aren't culls, but rather a new improved 30Q "141" cell :wink:

 

[goatman]

ya, when i saw looney tunes, i say, i say, i say, came blaring into my brain

since you remembered :lol: :lol: :lol:
have you tried reading his posts in foghorn leghorn yet?????

 

[goatman]

got a 14s5p of 30Q
1s had bad spot welds and is at 3.74v
14s, bad spot welds, at 3.68
the rest are at 3.77v

thats good news
i should be able to tear it down and get a 17s4p out of these cells

bad spotwelds on the negative ends






2 dented cells and the hot glue is falling off some cells once the nickel was strip was pulled



ground the spot welds and rewrapped, just need to equalize them next

 

[goatman]

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

and out of that 96 cell pack
6 are bad they self discharged to around 3.50v to 3.60v from 3.71v in 2 weeks

the other leftovers
39@ 3.702v
1-3.698
2-3.695
1-3.687
2-3.681
1-3.666
1-3.658
1-3.653

17s4p
1s-3.207
2s-3.207
3s-3.199
4s-3.199
5s-3.199
6s-3.197
7s-3.192
8s-3.192
9s-3.199
10s-3.199
11s-3.196
12s-3.197
13s-3.199
14s-3.194
15s-3.207
16s-3.191
17s-3.185

the other 9 are about 0.020v lower

 

[larsb]

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?

 

[goatman]

Finally! we got the word to call it

 

[eMark]

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?

These Samsung 30Qs have a reputation for higher self-discharge than other high energy dense cells. His testing procedure for these 30Q cells provides a means to separate the usable salvaged "regenerate" 30Qs from other 30Q cells having a higher self-discharge that he considers unregenerate.

6 are bad they self discharged to around 3.50v to 3.60v from 3.71v in 2 weeks

the other leftovers
39@ 3.702v
1-3.698
2-3.695
1-3.687
2-3.681
1-3.666
1-3.658
1-3.653

Not sure if he considers only those 39@ 3.702v as "regenerate" and other nine cells between 3.698v to 3.650v as borderline "regenerate" and any other 30Qs after 2 weeks rest below 3.605v as bad. This may be his benchmark for determining which salvaged 30Q cells are usable for his application when building his usable 30Q pack from salvaged cells.

 

[goatman]

ill do the quick equalizing for maybe 24 hrs then separate and wait 24hrs, measure voltage

all the same voltage goes together
different voltages i put to the side
i think thats a quick resistance test, i might be wrong, i dont know

so that group of 39 and 9 others were the ones i put to the side from 2 other salvaged cell builds, i think they were all equalizing together for about 2 weeks and have been apart for about a week


i could try and equalize for a month and do a resistance test to each cell once theyre all the exact same voltage
but this is quick and seems to be working for me

the pack i got yesterday with the bad spot welds was sitting at my battery guys house for months, voltages were close enough that i just equalized overnight and theyre already assembled into a new pack

ive got another salvage pack to do of vtc6 and after that ill figure out the resistance of all the left over cells to see what to do with them

 

[goatman]

this is the bad spot weld pack,(yellow, white,blue wrap) cells were equalized over night, built into 17s4p with 10mm magnets

charged to 70.2v, pack settled balanced at 70v/4.11v

my load tester is still measuring .03/.04v too low








3.2v



3.0v



2.5v



lowered amps to 0.49 just to discharge a little deeper



the groups were sitting at 2.74v except for the 3rd p-group, 2.69v after 2hrs
didnt bother charging it to 2.74v just left it at 2.69v and charged the pack back up

it settled 4.11v again

just going to do a 1amp regenerative discharge overnight



3.2v



3.0v



2.5v



bottom balanced at 2.72v and recharge

final discharge to 3.0v



heres the packs



pack 1 has 18 cycles on it, no problems

pack 2 was discharged to 3.0v and were watching that right now
after 1 month ill put it to use

pack 3 im doing the same as pack 2 for comparison its sitting at 3.10v right now

 

[goatman]

pack 2

april 15 / april 30
1s-3.185 / 3.214
2s-3.185 / 3.213
3s-3.185 / 3.199
4s-3.185 / 3.199
5s-3.185 / 3.206
6s-3.184 / 3.199
7s-3.185 / 3.193
8s-3.185 / 3.199
9s-3.185 / 3.199
10s-3.186 / 3.206
11s-3.185 / 3.199
12s-3.185 / 3.199
13s-3.185 / 3.206
14s-3.185 / 3.198
15s-3.185 / 3.214
16s-3.185 / 3.187 april.24 was 3.191v
17s-3.185 / 3.185

probably shouldve equalized the cells for a month before building but im not really worried about building a perfectly balanced pack from used cells. time to put it to use

pack 3
1s 3.192
2s 3.198
3s 3.185
4s 3.185
5s 3.192
6s 3.198
7s 3.192
8s 3.192
9s 3.192
10s 3.192
11s 3.192
12s 3.198
13s 3.191
14s 3.192
15s 3.192
16s 3.192
17s 3.197

 

[eMark]

Agree that the scientific notation to three decimal places is impressive. Finally got a versatile dc meter that reads up to five digit decimal place accuracy ... measurement accuracy reaches to 0.00001. When taking readings the 4th and 5th decimal digits are continually bouncing up and down every split second, but gradually going down over 1 minute. Evidence of the minimal power drain of even this little hand held digital meter when taking 18650 voltage readings.

Its advertised voltage measurement range is 3.60v~32.00v, but mine only reads as low as 3.89v before the screen goes blank. There are two settings ... one reads three decimal places (e.g. 3.894v), and the other to five decimal places (e.g. 3.89432v) with 18650 cells ... https://www.amazon.com/dp/B08FM1NPML?psc=1&ref=ppx_yo2_dt_b_product_details

Now, I can be more precise (three decimal places) come later this year when i UPDATE the degree of self-discharge of my experimental Vruzend 10S3P 30Q pack after 100 more cycles with cells equalized ACAP to 3.750v after 1 days' rest and more precise cell voltage readings again after for 14 days rest. The pack is now composed of twenty-one 30Q "141" cells and nine 30Q "6" cells. In February of '21 after 170 pack cycles in 2020 the self-discharge ranged from 3.73v to as low as 3.44v after resting 14 days. Initial equalizing to 3.75v with 3.75v-3.74V after 1 day of 14 day rest. Twenty of the cells were still at 3.75v-3.74v after 44 days. I decided to use the "141" 3.73v cell again as one of the new/fresh ten 30Q "6" cells showed significant self-discharge when testing with my MiBoxer C4.

I'm disappointed the KKmoon meter doesn't read below 3.890v as was planning to equalize all 30 cells ACAP to 3.750v after 1 days' rest before testing for any self-discharge again after 14 day rest. Do you know of an inexpensive stand alone hand held dc meter that reads to three decimal places as low or lower than 3.750v ?

 

[goatman]

not a clue
the extra 39 and 9 i decided to equalize with each other for a week and do a manual resistance test to them

 

[goatman]

april.30
pack 3--- today
1s 3.192-3.221
2s 3.198-3.221
3s 3.185-3.207
4s 3.185-3.207
5s 3.192-3.221
6s 3.198-3.221
7s 3.192-3.221
8s 3.192-3.220
9s 3.192-3.221
10s 3.192-3.220
11s 3.192-3.214
12s 3.198-3.221
13s 3.191-3.214
14s 3.192-3.214
15s 3.192-3.220
16s 3.192-3.217
17s 3.197-3.221

 

[goatman]

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

going to put it to use

 

[goatman]

16s6p vtc6, bad spotwelds











have 11s6p of good cells minus the one cell at 3.82v
so 65 cells
could make a 13s5p for my sons bike or a 16s4p for my boat
decisions, decisions :wink:

 

[goatman]

equalized 66 of the good with 22 that were at a lower voltage for a week. had 8 dead cells
all the batteries are at 3.96v
removed the foil and magnets off the positive side,
going to let them sit another week and recheck each cells voltage before building a pack

 

[eMark]

pack 2

april 15 / april 30
1s-3.185 / 3.214
2s-3.185 / 3.213
3s-3.185 / 3.199
4s-3.185 / 3.199
5s-3.185 / 3.206
6s-3.184 / 3.199
7s-3.185 / 3.193
8s-3.185 / 3.199
9s-3.185 / 3.199
10s-3.186 / 3.206
11s-3.185 / 3.199
12s-3.185 / 3.199
13s-3.185 / 3.206
14s-3.185 / 3.198
15s-3.185 / 3.214
16s-3.185 / 3.187 april.24 was 3.191v
17s-3.185 / 3.185

probably shouldve equalized the cells for a month before building but im not really worried about building a perfectly balanced pack from used cells. time to put it to use

How 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 ?

The best performing cells were: 1s, 15s, 2s, 5s, 10s, 13s ... the not so stellar were: 17s, 16s, 7S

pack 3

april.30........may.11.....may.30
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

going to put it to use

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 ?

What "regenerative" technique do you credit to bounce back voltage of +.043v over one month and no self-discharge from any of these salvaged 30Q 136 cells ?

The same apparent result with pack 2 (no self-discharge) except for possibly 16s & 17s from april 24 to april 30 ?

Do 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 ?