Half my 6s Lipo brick goes out of balance quickly. advice?

[Kin]

Hi,

So, I have 3 Lipo bricks (2 6s 3ah, 2 6s 5ah). I finally got my Eco6-10 charger to balance the packs. I discharged and charged both 3ah packs fine. One 5ah as well.

I'm struggling with this one last guy.

First time I discharged it using the Eco6-10 charger, early on I get a low voltage error. I use my battery medic to check individual cell voltages. Shit. I have 3.63, 3.65, 3.63, and 2.84, 2.83, 2.83.

Crap. So does this make that lipo pack useless? Is that a sign it's completely dead? I'm charging the packs right now in balance and I'm already at 3ah put in- I think I'll get to 4ah at least, so clearly the pack has some use. But I'm worried about actually running that pack since it got out of balance so easily. *UPDATE* The other 5ah pack actually has the same problem. Almost. voltages after discharge error were 2.84,2.83,3.2,3.6,3.6,3.6 (approximate). So 2 bad, 1 semi bad, 3 good.

I am kind of suspicious that 3 of the cells were equally out of balance. If I had a few dud cells, presumably they'd suck asymmetrically. Is this any sort of connection issue that i could resolve?

Thanks for any LiPo help.
-kin

UPDATES:
1)

I intended this light cycle to be a full 3.0-4.2. I did charge first, and I should clarify, for the original post, that my initial pack was in balance, discharged, out of balance, rebalanced, and discharged again (and out of balance again).

2) I checked my second 5ah pack, and unlike I originally indicated, it also is shoddy. Difference was that the first 5ah pack discharged with 3 good cells 3 bad, the second 5ah pack discharged with 2 bad cells 1 semi-bad and 3 good cells.

3) New Information: I forgot to mention that I had to add new X60 connectors to this pack, replacing the 4mm bullets. Nothing heated up too much, though indeed it was tricky to attach 10awg wire with a 46w iron. I dont think I screwed anything up, but could I have?

Lessons Learned:
---> For one, at my very low discharge (1/4th C) 3.6v is where I should expect a dropoff. So going to 3.4 you can expect the slight differences in capacity to register very different drops as they're plummeting in a steep way. However, the problems also reflect a greater problem; I do have 3/6 cells in each pack that can only do 3 or so Ah. I've been busy and not made any progress to maybe cannibalize one of the packs to make one good pack with 6 leftover useless cells.

Updates: Ohzee has a similar situation he wanted to add to the thread discussion. Page 3,

"

I did not want to start my own thread so just tried to find a similar one to ask a question.

Currently I have 18s4p 25c zippy flightmax that have been solid. Today after charging I was just double checking
to see how balanced they were. All looks good minus one pack. All cells were 4.15 and one was 4.0. I hooked it
up to the charger to balance and the low cell shot right up to 4.15 right away , but once the charger would balance
it went back to 4.0. I could even repeat this same behavior.

I am about to go take a ride and going to keep it on a cell log so I can see what happens under load. Sound like a
bad cell ? My concern now is it goes over the cliff and I have issues. Depending on what happens after this ride I may
order a new battery and swap it.

thanks in advance for your knowledgeable advice.

 

[neptronix]

It's possible that half of your charger suffered a stroke at some point or is just calibrated awfully.

To determine this, do a full balance charge all the way up to your preferred voltage, and then discharge each of your packs.

If they all show the same pattern, the issue is the charger.
If only one packs reacts this way, you certainly have an odd lipo pack... 3 cells sound like they are down about ~300mAH.

 

[ZOMGVTEK]

The ECO 6-10's are not very high quality chargers and I do not recommend balance charging with them.

You need to manually balance the pack and charge it with the 6-10 without connecting the balance plug. It's probably OK.

 

[miuan]

You charged the cells to 3.7V right? That is just about 15% charge. A fully charged LiPo cell would have 4.2V, check if that's what your charger is set for. If you discharge a brick under 3.5-3.6V per cell, some cells will just dive down while others keep the voltage for a bit longer as not all have equal capacity. This is why too low discharge is dangerous with LiPo cells. It gets to and under zero volts too fast if you only watch total voltage and have some serious imbalance.
However much more likely, the last brick may have had some initial imbalance between first and last 3 cells that got amplified by bringing them too low on discharge. If you charged them first, this would never happen. Try charging the last 3 cells to match the others' voltage, then charge the brick normally and see if they drift down again or not. Watch the cells' voltages several times during charge and discharge and see if and when they start to diverge.

 

[Kin]

It's possible that half of your charger suffered a stroke at some point or is just calibrated awfully.

To determine this, do a full balance charge all the way up to your preferred voltage, and then discharge each of your packs.

If they all show the same pattern, the issue is the charger.
If only one packs reacts this way, you certainly have an odd lipo pack... 3 cells sound like they are down about ~300mAH.

Hmm, not not sure. I could cycle the 3ah pack to see if your theory about the charger holds weight. The reason I didn't think the charger was at fault was is that the 3ah packs charged fine.

The ECO 6-10's are not very high quality chargers and I do not recommend balance charging with them.
You need to manually balance the pack and charge it with the 6-10 without connecting the balance plug. It's probably OK.

How do you manually balance the pack....? The thing is when I set to "balance charge" the Eco-10 does fine at balance charging them within 0.04 volts, for which I'm happy. The manual says during discharge it also monitors voltage...but that's just not true, it just checks occasionally for no <3v cells.

You charged the cells to 3.7V right? That is just about 15% charge. A fully charged LiPo cell would have 4.2V, check if that's what your charger is set for. If you discharge a brick under 3.5-3.6V per cell, some cells will just dive down while others keep the voltage for a bit longer as not all have equal capacity. This is why too low discharge is dangerous with LiPo cells. It gets to and under zero volts too fast if you only watch total voltage and have some serious imbalance.
However much more likely, the last brick may have had some initial imbalance between first and last 3 cells that got amplified by bringing them too low on discharge. If you charged them first, this would never happen. Try charging the last 3 cells to match the others' voltage, then charge the brick normally and see if they drift down again or not. Watch the cells' voltages several times during charge and discharge and see if and when they start to diverge.

Actually Miuan I charged the cells to 4.2v, though normally I would be charging these between 3.2-4.1, I intended this light cycle to be a full 3.0-4.2. I did charge first, and I should clarify, for the post, that my initial pack was in balance, discharged, out of balance, rebalanced, and discharged again (and out of balance again).












Thanks everyone for responses so far! I'm not sure I'm really any closer to knowing whats going on, though.

 

[ZOMGVTEK]

All of the 7 ECO 6-10 units I have used were very poorly calibrated and some cells can be off from .05V to .1V from a quality DMM. Its 'balance' mode is mostly junk due to this, and the fact that it wants to charge to 4.20V/cell. This is excessively high for standard E-Bike use and will decrease cycle life significantly.

You can manually balance by several methods. Charge at a very low current while having an external balancer running, or use a current regulated power supply to balance the pack cell by cell.

Also, Most cell monitors unevenly draw power from the pack, so do not leave them connected when not needed. The balance plug should be used for balancing, and occasional monitoring. No need to leave something plugged into it 24/7.

 

[vanilla ice]

Sounds like 3 bad cells to me. Does not sound like anything to do with the charger.

 

[Kin]

All of the 7 ECO 6-10 units I have used were very poorly calibrated and some cells can be off from .05V to .1V from a quality DMM. Its 'balance' mode is mostly junk due to this, and the fact that it wants to charge to 4.20V/cell. This is excessively high for standard E-Bike use and will decrease cycle life significantly.

You can manually balance by several methods. Charge at a very low current while having an external balancer running, or use a current regulated power supply to balance the pack cell by cell.

Also, Most cell monitors unevenly draw power from the pack, so do not leave them connected when not needed. The balance plug should be used for balancing, and occasional monitoring. No need to leave something plugged into it 24/7.

I actually am using it on Li-Ion right now (was using LiPo earlier). Not sure if that's important to you (you have used 7 eco 6-10 chargerS??), but Lilo setting charges to 4.1v.

Sounds like 3 bad cells to me. Does not sound like anything to do with the charger.

So I guess. Damn. Is there anything I can do? I bought them a while ago, about 4 months.

 

[ZOMGVTEK]

All of my ECO 6-10's only have a single Lithium charge mode, LiPo. It forces 4.20V/cell no matter what.

While its possible 3 cells are bad, I would assume its more likely something else is at fault. Unless I'm missing something, I don't see why 3 cells would all be consistently low around the same voltage, assuming they once were good.

 

[vanilla ice]

Eco-6 don't have a LiLo mode?? In that mode even if your charger is high by 0.1v like you're claiming, you're still OK.

 

[Kin]

All of my ECO 6-10's only have a single Lithium charge mode, LiPo. It forces 4.20V/cell no matter what.

While its possible 3 cells are bad, I would assume its more likely something else is at fault. Unless I'm missing something, I don't see why 3 cells would all be consistently low around the same voltage, assuming they once were good.

? Eco6-10 definetly has LiFe, LiPo, Lilo, and possibly one other mode. You need to go to "program" and go through that section. It's also how to get rid of the ugodly irritating buzzers and beeps. I'm not sure if you can assume the 3 cells were once good...because they're from a new pack, but, I am asking on the forum in part because I dont understand why they would all 3 be faulty to the same degree.

Eco-6 don't have a LiLo mode?? In that mode even if your charger is high by 0.1v like you're claiming, you're still OK.

I didn't really understand your statement. Lilo is actually low, which is nice. The charger goes from 3.0 to 4.1 on Lilo, and 3.0 to 4.2 on Lipo. It tapers off in the same way (near the end of charge). yeah, ok, thats all I can say; i didn't really get at what you were saying.

 

[dogman dan]

You've got a stinker pack. It's quite common. Three cells of that pack are toast if they consistently discharge that low while the others only go to 3.7.

So go buy some more. Then, don't ever take em below 3.5 v if you can. Never below 3.7 even better. In "normal use" stopping at around 3.8 helps em last.

Light cycle discharging them to 3.0? Wow, I'd hate to see a heavy cycle. I don't think you killed em though, you just found you have some bad cells in a new pack. It happens to all of us at some point.

Your charger being off .1v doesn't matter if it is. Not enough off to cause a problem. Some guys get their undies in a bunch if a pack is out of balance by .05v. I always have a bit of a laugh at that. That may be a lot in some applications, but when you run 20s 10 ah on a bike it's meaninless. Cool that you can measure it, but has no effect till it's at least .5 off in my opinion.

 

[pdf]

You've got a stinker pack. It's quite common. Three cells of that pack are toast if they consistently discharge that low while the others only go to 3.7.

So go buy some more. Then, don't ever take em below 3.5 v if you can. Never below 3.7 even better. In "normal use" stopping at around 3.8 helps em last.

Light cycle discharging them to 3.0? Wow, I'd hate to see a heavy cycle. I don't think you killed em though, you just found you have some bad cells in a new pack. It happens to all of us at some point.

Your charger being off .1v doesn't matter if it is. Not enough off to cause a problem. Some guys get their undies in a bunch if a pack is out of balance by .05v. I always have a bit of a laugh at that. That may be a lot in some applications, but when you run 20s 10 ah on a bike it's meaninless. Cool that you can measure it, but has no effect till it's at least .5 off in my opinion.

Dogman,
Your sig says "Never below 2.7". Is that a typo or am I missing something?

 

[dogman dan]

From Live for Physics classic lipo battery care post in this thread.
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9170&start=0

Those aren't the practical daily use, usable battery voltage range, but the drop dead store the pack in a fire box before it vents voltage limits.

So don't try to revive a pack that went to 2.6v or got charged to 3.4v. I't much more likely to have a thermal runaway now. Time to scavenge the good cells, and store carefully till you properly dispose of the damaged cells.

I'd call the practical voltages about 4.18v to 3.6. Charge to 4.2, and it just drops later to 4.15-4.18 depending on the age of the cell. And by 3.6v the cell has gone over the cliff and will drop voltage fast enough to let your screw up and get one cell below 2.7 pretty quickly.

 

[pdf]

From Live for Physics classic lipo battery care post in this thread.
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9170&start=0

Those aren't the practical daily use, usable battery voltage range, but the drop dead store the pack in a fire box before it vents voltage limits.

So don't try to revive a pack that went to 2.6v or got charged to 3.4v. I't much more likely to have a thermal runaway now. Time to scavenge the good cells, and store carefully till you properly dispose of the damaged cells.

I'd call the practical voltages about 4.18v to 3.6. Charge to 4.2, and it just drops later to 4.15-4.18 depending on the age of the cell. And by 3.6v the cell has gone over the cliff and will drop voltage fast enough to let your screw up and get one cell below 2.7 pretty quickly.

OK. Just checking. Thanks.

 

[Kin]

Dogman, thats is kind of demoralizing. *(at the same time, thats what I made this thread for- to get a concrete idea, so I know for sure).

I'm not sure. It'll be a bit of time before I have the money to buy to get some more packs [dont work much during the school year]. So, if hobbyking gives me more duds second time around...that's just not a "bad luck" situation that's ok. It's just. ARRGGh. It's frustrating enough to get bad cells the first time. I didn't figure that this would actually happen to me for *two* packs. Assumed it was a "1 in 100" (still pretty high) failure rate.

In some sense I think perhaps I need to simply buy some LiMN cells from people on these forums. That way at least I'm not screwed again.

 

[www.recumbents.com]

What is the C rating on these packs? I'm betting 15 or 20C. Correct me if I'm wrong but it seems to me most of the out of balance / puffy / thermal runaway packs are the ones with lower C ratings. Maybe these are all just the runt cells culled from the 30C+ cell manufacturing?

I personally am sticking to 30C and higher lipo packs.

-Warren.

 

[vanilla ice]

I didn't really understand your statement. Lilo is actually low, which is nice. The charger goes from 3.0 to 4.1 on Lilo, and 3.0 to 4.2 on Lipo. It tapers off in the same way (near the end of charge). yeah, ok, thats all I can say; i didn't really get at what you were saying.

Yea I only use LiLo mode. I was replying to ZOMG who said he got some lousy chargers. I've actually never cross checked my chargers voltage readings with any thing precision to see how off they might be.. They seem to all line up with each other just fine though.

 

[neptronix]

You still haven't checked to see if your budget charger was the culprit .... ?

3 cells in a row of equally bad condition is highly improbable.

 

[Kin]

You still haven't checked to see if your budget charger was the culprit .... ?

3 cells in a row of equally bad condition is highly improbable.

Hey Neptronix, actually, I thought I had. You see, I've also discharged a set of 6s 3ah Lipo from 4.1v to 3v and seen perfectly even discharge. That said, you have a decent point one one level- assuming they put together the cells the each way, it's extra weird because the order is the same for both bad bricks-
"Bad - Bad - Bad - Good -Good -Good
&
Bad-Bad-SemiBad-Good-Good-Good".
(As per the ribbon cable).

I'm not sure how you suggest to check if my budget charge is the culprit. My example of the 3ah pack I thought would be enough to show my charger is the culprit. Alternatively, I can discharge with my battery medic, but well two problems there. 1, it balanced while it discharged (I *think*), and two, it's going to about 2 days to discharge the pack, and I might just kill it at that. I can charge up to say, 3.8v, then from there perhaps discharge. Anyway. How should I do it?

What is the C rating on these packs? I'm betting 15 or 20C. Correct me if I'm wrong but it seems to me most of the out of balance / puffy / thermal runaway packs are the ones with lower C ratings. Maybe these are all just the runt cells culled from the 30C+ cell manufacturing?
I personally am sticking to 30C and higher lipo packs.
-Warren.

It's the 20c pack. If you look at the weight of the packs, though, it's quite likely that they're not just runt cells. The 20c,30c, etc, packs have substantially different weights even for the same voltage and amp-hours. It's quite likely that the higher C ratings are constructed differently, and at the very least have substantially different cathodes and anodes to bear the fact they have to deal with a different voltage and chemical interaction. It's possible, however, that Hobbyking has zero quality control on the cheapo packs, but actually has more stringent control on the more expensive ones.

 

[neptronix]

To test it, i would run multiple packs through it and see if you get the same results.
Sounds like you already did that ... and got eerily similar results.

Have you checked the cell voltages with a voltmeter? is the voltmeter telling you a different story than the charger?

It just seems weird that you would have multiple packs with the same flaw ...

 

[Kin]

Hey Neptronix, yeah. That was one of the reasons I originally was confused. It seemed weird the cells were bad to the same extent. But I dont really agree that I got eerily similar results. I got similar results for the two 5ah packs. I did **not** get the same results for the 3ah pack. The Eco6-10 doesnt actually give individual voltage readings. The unit measures them, it just doesnt display them. So my situation would go like this. 1) Eco6-10 alarm goes off. Display says something like <<Low Voltage Cell>>. I then check with the battery medic. Oh, shoot! Indeed, three cells are shit.

So, the measurement is being done by the eco6-10, but not reported, and then again checked with the battery medic. I wont have time until next week to replicate the discharge situation again [But I mean, the 4.1v my cells are at right now is the same as my voltmeter shows. I doubt battery medic would be accurate right now but now accurate when the cell is discharged] (I'm going away this weekend and there's a place on campus I get my 12v input, since my power supply is not working at the moment).

 

[ZOMGVTEK]

If you hit the button closest to the 'play' button on the ECO 6-10 while charging, it displays cell voltages. I'm fairly sure it is the + button. Pressing the - button also shows additional information, such as input voltage and temp.

 

[Kin]

If you hit the button closest to the 'play' button on the ECO 6-10 while charging, it displays cell voltages. I'm fairly sure it is the + button. Pressing the - button also shows additional information, such as input voltage and temp.

Oh, thanks! Good to know.

 

[dogman dan]

Bummer that you got a bad pack when buying just two. My bad pack rate is more like one in ten than one in a hundred. All of the bad packs were from a batch of 4s packs. So the failure rate for that particular choice was actually 100%.

Bear in mind though, that before HK came along you'd have paid 2-3 times the price for those things. I now only buy from the US warehouse, so returning one can be easier.