bringing back makita V limn Konion from zero volts

[Matt Gruber]

Got 10 makita v packs from Doctorbass today.
I'm learning on the worst cells first, as i have no experience with limn (just SLA LOL)
My theory is that one cell has a defect and cell #2 in 2p gets sent to zero, but it was not defective.
So i took 4 dead pairs, and sure enough 4 were dead and gone forever, and after a jolt, 4 are charging fine!
It is just an experiment, not for ebike use. maybe lights or an old drill is my goal.
if anybody wants more details, just ask.
Maybe they will all be dead tomorrow!

 

[Teh Stork]

They will have poor performance and high self discharge rate. Cells that rest at 0V degrade(internal shorts are created).

 

[Matt Gruber]

They will have poor performance and high self discharge rate.

/
compared to what? my 10 yr old ni-cad drill runs 2 minutes and dies. my LED flashlight is too dim to use.
Worse than that? we will see tomorrow if they go dead.
They need to last at least a week or i won't bother with these at all.

 

[liveforphysics]

A cell that has sat at 0v has experienced the copper foils dissolving. As you recharge this cell, it can make copper dendrites anywhere it likes to create internal shorts. Can range from happening on the first cycle, to never, but if you need to trust the cell, go with something that has never been below ~2v after it's initial formation.

 

[spinningmagnets]

If they are the 18650 cells (18mm diameter, 65mm long, cylindrical), And you have a few laying around, I recommend getting a single-cell flashlight for them, they are very bright. Go to ebay and search for 18650 flashlight.

I will come back later to post the link for the one I got when I get home (work computer doesn't allow ebay).

 

[docnjoj]

I had some good luck restoring 6 Fatpacks that were drained to 0volts by my leaving the controller on for 3 or 4 days. They are still working about 2 years later, although they are paralleled with a 10ah Ping that is good for about 8 ah. My wife can still get 20 miles out of the combo with a teeny bit of reserve on a warm day. We will see tomorrow about cold weather. I got the bungee tow rope.
otherDoc

 

[Matt Gruber]

I had some good luck restoring 6 Fatpacks that were drained to 0volts by my leaving the controller on for 3 or 4 days. They are still working about 2 years later, although they are paralleled with a 10ah Ping that is good for about 8 ah. My wife can still get 20 miles out of the combo with a teeny bit of reserve on a warm day. We will see tomorrow about cold weather. I got the bungee tow rope.
otherDoc

Thanks for chiming in! 2years of use, that others would recycle! Nice save!
.
So 12 hours later 3 of 4 cells are unchanged!
#4 dropped .2 volts, so i guess it has that dreaded dendrite disease.
.
my flashlight is so old, it fits 3 c cells in line. so an 18650 fits right in.
.
thanks for all the comments; post your recovery test results, good or bad! i'm here to learn.

Edit. So i practiced soldering on 2 hopeless cells. Good thing, as i learned how easy the + can SHORT!
I made a fixture to hold 3 cells.
flux is a MUST.
i used a damp sponge to cool the cells FAST, as i tore off the tabs (thinking the zeros were all bad)
Total time was 1 hour LOL for 1p3s Slow but none shorted so i'm happy as this is my first time.

 

[Matt Gruber]

What better way to learn, than with an out of balance pack, without a proper charger?
So i discharged the recovered 1p3s at 2.4a for 20 minutes.
BEFORE they were not balanced
4.21v
4.08
3.96
after 18 min while being discharged
3.60v
3.56
3.32
AFTER a 15min rest
3.80
3.73
3.50
Can anyone estimate the full AH from this info? LiMn V cells.
Thanks!

 

[Matt Gruber]

so i balanced them closer
4.05
4.06
4.15
tested to 30 min 2.4a. thats 1.2ah 80% of the 1.5 when new. these were dated 6-11, so 2 years in a power tool, then months at 0.00 v.
i'm very pleased with these results.
here is more info
time @ voltage
5 min 11.27
10m 11.05
15m 10.83
20m 10.49
25m 10.09
30m 9.66 final under load v's 3.14v, 3.19, 3.33
after 15 min rest 3.35,3.38, 3.39
what do you all think? Thanks for reading!

 

[fechter]

I've brought back dozens of 18650 Panasonic laptop cells from zero volts. It's important to charge them very gently (like C/100) until they get up into the healthy range somewhere around 3.0V, then you can increase the charging rate.

If you blast them with a high rate when they are too low, they could go pyrotechnic or at best cause more loss of capacity.

 

[Matt Gruber]

Hi fechter!
Do other chemistry react the same as limn? Do they get dendrites that short the cell?
How to remove shorts other than high amps to destroy them like a fuse?
Maybe i'm doing this all wrong. But, the 3 cells are holding steady so far.
Thanks! Maybe these Konions can take a lot of abuse without complaint? They are from the scrap pile, so i can experiment.

 

[Matt Gruber]

Well i did some research and li-ion phones do have a pre charge 1/10c charge to get to 3.00v when it is over discharged. Then normal charge starts, 1/2c.
Don't know if Konion is different in principle, but probably not.
So on a 2nd batch of 0-0.6v cells, i gave them 5 seconds at high amps and they all were not shorted, so i'm doing 1/10-1/5c to 3.5v, then regular 1-1.5c, to 4.00v, then slow charge to 4.10

And i do measure actual AH capacity. All it takes is a stopwatch, load tester, ammeter, and a little math!

 

[fechter]

Hi fechter!
Do other chemistry react the same as limn? Do they get dendrites that short the cell?

I'm not sure about that. My only experience with dendrites is with NiCd batteries. Once the dendrites punch through the separator, it leaves a hole that won't go away. You can blow the dendrites away with a high current pulse, but the cells always seemed to fail shortly after that anyway.

With my LiCo laptop cells, they all seemed to come back to life, even after sitting at zero volts for about 2 years. I haven't had any that failed to take a charge. The cells were quite 'used' before being left to sit, so the capacity was lower than the rating, but all the ones I tested came back with about 80% of rated capacity which is proabably close to what they were before being stored.

It would be good if you had some way to measure the actual Ahr capacity. Battery analyzers are pretty expensive, but something like one of those cheap volt/amp/Ahr meters off ebay combined with a load resistor might work.

I'd suggest attempting the low C rate charge initially and any that don't come up may be candidates for blasting.

 

[cassschr1]

What charger are you using?
Why are you giving them a high amp blast Initialy. just curious.

 

[Matt Gruber]

Why are you giving them a high amp blast Initialy. just curious.

Good Q!
I don't want to waste time on a shorted cell. 1st batch of 8 had 4 shorted, so i knew in just 15 seconds.(now i only give it 5 seconds)
Dont have a proper chrger yet, so i have to babysit. Plus the Doc says limn rarely if ever come back from dead. So i don't want to waste lots of time. I'm learning, so reject cells teach me lots without risking a good cell.

 

[Matt Gruber]

so i balanced them closer
4.05
4.06
4.15
tested to 30 min 2.4a. thats 1.2ah 80% of the 1.5 when new. these were dated 6-11, so 2 years in a power tool, then months at 0.00 v.
i'm very pleased with these results.
here is more info
time @ voltage
5 min 11.27
10m 11.05
15m 10.83
20m 10.49
25m 10.09
30m 9.66 final under load v's 3.14v, 3.19, 3.33
after 15 min rest 3.35,3.38, 3.39
.
after 5 days still 12.20 v. so in an old drill they go.
the 2nd batch of 8 also produced 3 that look good, same recovery with a 1/5c as a 1c chrge, so i don't see any obvious benefit to slow charging liMN cells. Other chemistry may vary.
what do you all think? Thanks for reading!

i'm sure glad i built a 1-53a load tester 7 yrs ago. 1.2ah sound good to me.

 

[John in CR]

Don't waste your time unless you're some kind of scientist researching battery improvements and will open the cells up afterward, OR you're researching the potential usefulness of nearly dead batteries for static applications...eg using free batteries that would otherwise be destroyed. It will be so labor intensive though that I can't imagine viability.

There's no way to reverse the chemical reaction that took place inside the cell once the voltage was too low, so it's really not worth the fire risk.

 

[Matt Gruber]

Don't waste your time unless you're some kind of scientist researching battery improvements and will open the cells up afterward, OR you're researching the potential usefulness of nearly dead batteries for static applications...eg using free batteries that would otherwise be destroyed. It will be so labor intensive though that I can't imagine viability.

There's no way to reverse the chemical reaction that took place inside the cell once the voltage was too low, so it's really not worth the fire risk.

Hi John!
I've read dozens of your posts doing searches. I sure appreciate all your efforts!
Just got 2 old, 1985 Skill drivers working, they are 130 rpm. And a craftsman 18v drill 350/1350 rpm. I don't know that any hobby that one enjoys is a waste of time. I could of watched a movie, instead i did this. How else am i going to school myself in the handling and use of konions? I'm working with 1-3 cells at a time. Would you suggest i build a 72 cell pack with no limn experience? I'd rather start out real small for now. I've delayed buying limn since 2007, a few more weeks or months won't matter.

Please expand on the fire risk with Konion LIMN. I could not find any LIMN fires in search. How does this risk compare with SLA? They can easily set a fire too.

Thanks for years of helpful posts!
matt

 

[999zip999]

Yes they do catch fire. I have pulled them out of a makita pack just to see a small flame coming out of the top ( No just carefully pulled out ). That's with 53 makita packs or 530 cells. It just takes one for a fire. Or when soldering a ball of solder can fly off and under the tab and short. A very small solder ball when you put a hot iron on the tap with flux a small ball can and will jump off and go where ? Who knows. But with 150 solder joints it just take one for a chain reaction of heat and fire. So look it over close. I would use the 2.5v and above cells.
Doc's battery was pulled down slow for 3 days and were new unopen packs. Not abused returns. So be careful there are alive not just pretty green cells.

 

[Matt Gruber]

999zip
JEEZ you shorted it out Life is not risk free. This is why insurance sells well. I agree the Konions short way too easily! Im using the makita cradle and slipping the plastic tab under the + tab in the center. Has anyone tried this? Have to be real careful with these for sure.
.
I just added my occupation to my sig, as i realize you guys think you are talking to someone with no experience.
I guess that's my fault; how would you know. Sorry

 

[fechter]

Are most of the failed cells shorted? They could fail sort of open too, like with very little capacity.

 

[Matt Gruber]

Are most of the failed cells shorted? They could fail sort of open too, like with very little capacity.

good Q!
today another cell went bad, one that was tested ok 2 days ago. i noticed this makita pair was down to 3.81 after 2 days. the others were 4.04. so i cut the tab connecting the 2. within 2 hours it was dead! the other was still 3.81
so, i did a capacity test on the bad cell. charged 1.5hrs around 1c, no precharge, to 4.15.
results
amps.......volts..........minutes...................temp of cell.
2.75......3.83
2.64 3.67................5
2.63......3.63 10
2.6.........3.56.............15
2.56.........3.44............20..........................85f
2.51...........3.32..........25...........................86f
2.45..........3.17...........30...........................86f
2.38..........3.00............32..........................87f
........at rest 3.33
about 1.3AH! (new 1.5-1.6)
still packs a punch! maybe good for a boost pack
EDIT so i gave it 1/2 hour to rest was 3.36v BUT within 1 minute it was 2.49v, no mojo, have to pedal

NONE of the failed cells heated up, and i suspect the ones that took a charge had plenty of power as they stayed cool(low internal resistance)

 

[Matt Gruber]

installed a DVM on my new ebike.
this single cell test is to learn when i might detect a bad cell in a 9 cell 2p string(makita pack)
amps........volts.........minutes
4.44........3.84..........start of test
4.26........3.64...........5
4.18........3.52...........10
4.16........3.49............11
to calculate AH:
11/60=.183 hr x 4.23amps= .78 AH
at this point a normal string will drop to 31.5v, and could trigger the LVC. Everyone says cells last longer with a shallow DOD, so it is a good point to stop the test now, and when riding the bike. Might not need the DVM if the LVC works as advertised.(just time how long to LVC on a not windy day)
My goal is to make it easy to detect a bad cell, and make the pack easy to service.
.
EDIT
this shows how fast the lvc should trigger if a bad cell in 2p makes it run on 1p9s
single cell test
6.66a.......3.71v...........start
6.45........3.57............1 min
6.40........3.63............2
6.35........3.51............3
.............3.49 in just 3 min 20 sec! and bike speed would be down with less amps 6.4 instead of ~8.5

 

[John in CR]

My goal is to make it easy to detect a bad cell, and make the pack easy to service.

Make the pack with only good cells and then no service is required. That's the beauty of Konion packs, no BMS, no servicing, just bulk charge and ride. If you start seeing more voltage sag than usual, then something's up so check on individual block voltages.

 

[Matt Gruber]

Hi John!
I'm making a boost pack with dubious cells. It will add range when switched in, but, should it sag, it will be switched out.
Unlike your fine workhorse, my ebike might sit for a month or 2 or ?, and cells could self discharge and need attention. So I'm going to make the entire pack easy to service. Only about 72 cells max, nothing on the scale of your bike.