Max. cell imbalance LiPo?

[The Bean]

What's the maximum cell imbalance (max. V - min. V) you'd run or store your LiPo with?

I currently don't have any poorly balanced LiPos, but this would be good info to have.

 

[Jerold]

Each cell is an individual battery, so the difference on the storage charge doesn't really matter too much as long as it's in the acceptable range. Since storage charge is typically 3.6-3.8V per cell you've got some margin.

I always have the charger balance the battery when I do a storage charge so they aren't off by more than a few mV at most, typically see less than 20 mv (0.02V) difference. Some of that is due to the accuracy of the battery checkers too.

It's just my opinion, I'm sure other will have different opinions.

 

[TL01magic]

What's the maximum cell imbalance (max. V - min. V) you'd run or store your LiPo with?

I currently don't have any poorly balanced LiPos, but this would be good info to have.

I have a pair of 6750mah 3s and by mistake i drained one down to low 3v range

two of the cells cannot reach 4.2v anymore. they get upto 4.15v. only one charging so far and did not notice any battery temp differences. not warm or anything. That said, i would go more than 0.5v...and even that is kind of allot.

 

[Jeckler]

Kinda bringing this thread back from the dead... at least it's still warm.

I have a v3 Kraton and have 2 Lectron Pro 6S packs; 5200mah, 50c. They're both the same age as the truck, 3.5 years old. One of them recently developed a .04v imbalance on cell 1, at lest at storage (3.85v). I honestly don't think either pack has more than 15-20 cycles, they're just old.

I've been trying the last couple of days to even the pack back out by first discharging to 3.7v (per cell), then back up to storage at 1amp, then yesterday to 3.5v and this morning back to storage at .3a. The .04v imbalance is consistent throughout each cycle, up and down, and at both ends.
I use iCharger 206b's and it shows the same on either charger, plus the other pack is fine, within .003.

Should I bite the bullet and retire this pack?

 

[LibertyMKiii]

Kinda bringing this thread back from the dead... at least it's still warm.

I have a v3 Kraton and have 2 Lectron Pro 6S packs; 5200mah, 50c. They're both the same age as the truck, 3.5 years old. One of them recently developed a .04v imbalance on cell 1, at lest at storage (3.85v). I honestly don't think either pack has more than 15-20 cycles, they're just old.

I've been trying the last couple of days to even the pack back out by first discharging to 3.7v (per cell), then back up to storage at 1amp, then yesterday to 3.5v and this morning back to storage at .3a. The .04v imbalance is consistent throughout each cycle, up and down, and at both ends.
I use iCharger 206b's and it shows the same on either charger, plus the other pack is fine, within .003.

Should I bite the bullet and retire this pack?

iCharger is one of the top in the industry and does a good job of balancing. It sounds like that one might just be at that point of retirement...

 

[SrC]

I have a pair of 6750mah 3s and by mistake i drained one down to low 3v range

two of the cells cannot reach 4.2v anymore. they get upto 4.15v. only one charging so far and did not notice any battery temp differences. not warm or anything. That said, i would go more than 0.5v...and even that is kind of allot.

You could always try charging those 2 cells individually.Technical aptitude applies here however. But it can work. You never stated what the IR's were when those cells were found lower than the others. But honestly if it is bricked, it is your own fault. Crap happens. Hopefully never happens again.
The pack will still work for bashing if it is not puffed up. For speed running...Not the best pack to use at all.

 

[Jeckler]

So I'm impatient. I ended the .3a charge at around 3.9v per cell and balance charged the pack at 2C (10.2a). All cells within .1 at the end. Highest IR was 5, lowest 3. It took a good 35 minutes to finish once it switched to CV. I forgot how much energy was put in though.
Ran the 6S Kraton out in the field to LVC (8 minutes) and got the pack nice and warm. Immediately brought it in and storage charged at 2C. When done, IR was 2-1-1-1-0-0 after 5 minutes.
I'll keep it for a while, but will be looking for new packs eventually. It seems I might have better luck find "good" 3s packs than 6s though.

 

[Jerold]

So I'm impatient. I ended the .3a charge at around 3.9v per cell and balance charged the pack at 2C (10.2a). All cells within .1 at the end. Highest IR was 5, lowest 3. It took a good 35 minutes to finish once it switched to CV. I forgot how much energy was put in though.
Ran the 6S Kraton out in the field to LVC (8 minutes) and got the pack nice and warm. Immediately brought it in and storage charged at 2C. When done, IR was 2-1-1-1-0-0 after 5 minutes.
I'll keep it for a while, but will be looking for new packs eventually. It seems I might have better luck find "good" 3s packs than 6s though.

If your battery is warm the inner cells will stay warmer longer than the outer ones longer. So if you let them sit for a while (15-20mins), let them cool down before you try to do storage or recharge you should get better results. Then do the storage charge slowly. Hammering on them to charge is tough on the batteries.

My routine is to discharge them down to less than storage if needed, then set the storage charge at like 1/2C. It takes a while but it's much easier on the battery, I get a better balance because heat is not part of the equation and I don't generally care about the time, they get (dis)charged outside on the cement anyway.

In the end, the voltage and IR are never exact, they can change depending on a lot of factors, so if it's 3.7V/cell or 3.75V/cell it doesn't matter too much.

How did you get 0Ω IR? That doesn't make sense.

 

[SrC]

So I'm impatient. I ended the .3a charge at around 3.9v per cell and balance charged the pack at 2C (10.2a). All cells within .1 at the end. Highest IR was 5, lowest 3. It took a good 35 minutes to finish once it switched to CV. I forgot how much energy was put in though.
Ran the 6S Kraton out in the field to LVC (8 minutes) and got the pack nice and warm. Immediately brought it in and storage charged at 2C. When done, IR was 2-1-1-1-0-0 after 5 minutes.
I'll keep it for a while, but will be looking for new packs eventually. It seems I might have better luck find "good" 3s packs than 6s though.

I prefer to charge or storage charge my packs after a 40 min "cool down" at a minimum. Even if the pack is only slightly warm after bashing. Balance cycle always is the longest portion of the cycle. Normal.
Can't rush a lipo balance charge. Patience here.
For best durability and run times, you always run your packs as soon as possible after a full re-charge. Just allow a cool down first. Letting them rest a bit if they were just discharged. And also Storage charge them as soon as possible after use. They will live much longer. Getting the most out of them.
Letting them sit Discharged or Full charged for days on end will ruin them for sure. Sometimes this causes the puffing of a cell or two.
They store best at 3.80-3.85 volts per cell. This is the condition they are in when new out the box. Give or take. I specifically set my ISDT Charger to storage charge mine at 3.85v/cell. If they sit unused for months, I will check them and put them on the charger for another Storage charge cycle. May take only 2- 3 mins to bring them up to 3.85 v/cell again. Lipos sitting unused for long durations always lose volts. Don't neglect them. Get yourself a decent Lipo Testor if you don't have one already. An inexpensive tool compared to the $$ that lipo packs cost. I keep it with me when out bashing too.

 

[Jerold]

They store best at 3.80-3.85 volts per cell. This is the condition they are in when new out the box. Give or take. I specifically set my ISDT Charger to storage charge mine at 3.85v/cell. If they sit unused for months, I wil check them and put them on the charger for anther Storage charge cycle. May take only 2- 3 mins to bring them up to 3.85 v/cell again. Lipos sitting unused for long durations always lose volts. Don't neglect them.

I've always been little confused by this. From what I understand that is the "resting voltage". I've also seen different articles and postings with conflicting values, so I just follow what's on the battery.

I also try to check them monthly. I keep a battery checker with them and it's easy to do.

 

[SrC]

3.80-3.85 / cell storage volts seems to be the concensus. Give or take .0X v is negligeable.
Again, lipos new out the box are in this range. And for a reason. So they sit stored in inventory best for the consumer when ultimately purchased. It's just how lipo chemistry works.
I have received Lipo cells that were far below. They are questionable and I have returned them. A sign of bad production runs, bad cells or they just sat very long in inventory. New, but very old stock. Food for thought. Always check lipo's well right out the box and immediately. Lipos can be a mixed bag sometimes, regardless of price and brand. Bad ones just happen from time to time. Just takes one bad cell to ruin a new pack. I have gotten new packs that smelled of Lithium polymer . Very strong and Sweet smell. I return them. They are NG. Many sellers should not even argue. They are defective and dangerous when they smell like that.. Oxygen in the air should never react with any Lithium polymer that is "out gassing" . How fires starts. They were just poorly mfr'ed. Poor QC. The cell(s) were poorly sealed.
Age, regardless of how many times cycled as well as number of cycles is what normally depletes a lipo. And High humidity is a lipo's worst enemy over its lifespan and damgerous. China has a serious bad issue with all types of Lipos catching fires. Read between the lines. So all lipos can be dangerous. This industry is poorly regulated, like much of China. The majority of Global lipo production occurs there.
I find my lipos on average only last approx. 50-60 cycles before they start to peter out. Some still work ok. Just not the best run run times, no matter the brand or price. Proper and consistent Care and Feeding promotes a longer life.
The lipo industry claims they should provide way more use/cycles out of them. But that is in a perfect environment. We really abuse the crap out of our lipos in reality. Considering how we actually drive our rigs and all, and the extreme environments we use them in as well.


Edited.

 

[Jerold]

3.80-3.85 / cell storage volts seems to be the concensus. Give or take .0X v is negligeable.
Again, lipos new out the box are in this range. And for a reason. So they sit stored in inventory best for the consumer when ultimately purchased. It's just how lipo chemistry works.
I have received Lipo cells that were far below. They are questionable and I have returned them. A sign of bad production runs, bad cells or they just sat very long in inventory. New, but very old stock. Food for thought. Always check lipo's well right out the box and immediately. Lipos can be a mixed bag sometimes, regardless of price and brand. Bad ones just happen from time to time. Just takes one bad cell to ruin a new pack.
Age, regardless of how many times cycled as well as number cycles is what depletes a lipo. And High humidity is a lipo's worst enemy over its lifespan.
I find my lipos on average only last approx. 50-60 cycles before they start to peter out. Some still work ok. Just not the best run run times, no matter the brand or price. Proper and consistent Care and Feeding promotes a longer life.
The lipo industry claims they should provide way more use/cycles out of them. But that is in a perfect environment. We really abuse the crap out of our lipos in reality. Consisering how weactually drive our rigs and all, and the extreme environments we use them in as well.

The reported maximum cycles is in a controlled environment. It's like the old MPG ratings, where you could buy a Big Block that got 20MPG. What they didn't tell you is that was down hill in a hurricane.

As always it's buyer beware and I just assume they all lie. So pick the lies you like.

 

[SrC]

You are basically correct sir.
I believe , the MPG rating tests are actually just done on a Dyno, and they use Propane for fuel in many cases. Then just submit the test results to the respective governing authority, who accept whatever it is.
That is why MPG results are usually BS. Not real world use data.