Battery Charging question Lico 8s

[gaisom]

I am using an icharger 1010B+

I noticed on one pack when I went to charge it that cells 1 thru 7 were from 3.70 to 3.74
However, cell 8 showed at 4.10 and made me think it had not discharged, like it had a bad connection. The voltage for the whole pack reading was correct though. I checked the balance port using my Low voltage alarm and it shows that cell 8 is indeed at 4.10v

What could have caused this?

BTW, I am very dissappointed with the balance charging on the 1010 b+ I expected it to be very accurate. Instead I have variances of from .02 (3.98) to .05 (3.93) between the 8 cells in every pack, and none of them came up to the 4.10v that I have the charger set up to balance at. I rechecked the program and it was set on balance charge with an upper cut off of 4.10v

Any suggestions?

 

[dogman dan]

This is very odd. For the remaining cell to be still at fully charged 4.1v, while the others are close to 90% discharged can only happen two ways.

1, the pack is wired wrong, with the + wire on cell 7, not cell 8. So cell 8 never got discharged. This should be obvious if total voltage never reaches what 8 cells should be.

2, the cell 8 got really horribly overcharged! That would make cell 8 very dangerous to use now.

 

[gaisom]

I know it did not get overcharged as I checked them all and had alarms on each balance cable which I checked when I installed the alarm modules.

I am going to run it again, discharge it down to about 3.2 and see what they show then.

 

[Hillhater]

The voltage for the whole pack reading was correct though...

What was that total pack voltage measurement ??

 

[dogman dan]

So at the start of the ride, that pack had about 32.8v ? 4.1 x 8. If somehow the pack was manufactured with the red discharge wire on the + of cell 7 instead of cell 8, you'd expect a pack voltage of 28.7, when charged to 4.1v. Your charger would have balked at charging it to 8s voltage. So I seriously doubt this is the problem.

That leaves some kind of slip up on how you are reading the voltages. Like a device is not working right on all 8 cells, or your regular voltmeter (DVM) needs a battery.


You are getting 4.1v on that cell with several different voltmeters right? And they work fine on other packs?

To find out what is really going on, you might want to peel the shrink off of just the top of the pack. Then you can put a DVM directly on the cell tabs. And see if it looks like there is some defect in the balance plug wires.

 

[gaisom]

I made the pack myself, and I have opened it up and checked it.

Cell 8 is my Negative battery terminal. The Pack reads 32.8 charged. I am going to get a chance to ride it today I hope (waiting for the rain to stop).

I only have one voltmeter which works normally on every pack.

I am thinking about replacing cell#8 with another new cell and see if anything changes since I have already opened up the Pack. Perhaps I have a Super Cell :lol:

 

[dnmun]

do you use a balancing charger and have one cell be so far different from the others? don't cut it open until you know why.

 

[wesnewell]

Cell 8 should be the positive terminal if you wired it per standard.
http://scriptasylum.com/rc_speed/lipo.html
If you post a photo of the open pack, maybe someone can figure out what's wrong.

 

[gaisom]

I didn't set it up as standard, but they will be now.

OK, I rode the bike till the voltage reading was 24.28v and when I checked all the cell they are reading normally now, so I must accept that I screwed up somehow. Thanks for all the info guys.

 

[gaisom]

I can't see where there would be a standard as to which cell is in what position. As long as you Connect the Positive terminal to the Positive battery post and the negative to the negative post I don't see how there could be a difference?

 

[wesnewell]

If you don't use balance wires it doesn't matter. There's just a pos. and neg. end. Now start wiring each individual cell to a balance charger. They have to be in the right order. That's why there's a standard.

 

[gaisom]

In setting up my packs I always attach the balance wires starting from the Neg Connection of the battery pack. This is so I can always have my balance wires soldered to the enclosed end of the 18650's.

When I first started soldering them up I had a few cells where I put too big of a solder spot on the Positive connection of the battery. What this did was to cause a small short of the cell on the positive end. I would get the pack halfway soldered up and feel heat where it wasn't supposed to be. The cell would be shorting internally as I said above and just keep getting hotter and hotter until it finally fully discharged to 0.00 The really bad thing is that unless you keep checking for Heat it is very hard to find the cell that is running away on discharge as there is no visual indication. Makes for some hurried unsoldering to get that bad cell out of the pack.

I suspect that this is one of the main causes of fire in recycled laptop cell battery packs. It also doesn't always show up right away. I had one case where the battery pack had been assembled, and I was balance charging the pack when I got a low balance port shutdown. When I picked up the pack I burned my finger on the internally shorted cell which had failed during the second charge/discharge cycle. In every case where I have had a cell failure during balance charging (two cells on one pack at the same time it has also caused overcharging of the remaining cells. Twice I have had to throw out a fell 10 cell pack because of the internal shorting of cells causing the remaining cells to charge higher than 4.3 volts. In one case it charged the other 8 cells to 4.53 volts and left two at O volts. Luckily I was keeping close tabs on this charge as I was trying out Parallel charging for the first time. Not gonna do that again.

 

[dnmun]

In setting up my packs I always attach the balance wires starting from the Neg Connection of the battery pack. This is so I can always have my balance wires soldered to the enclosed end of the 18650's.

When I first started soldering them up I had a few cells where I put too big of a solder spot on the Positive connection of the battery. What this did was to cause a small short of the cell on the positive end. I would get the pack halfway soldered up and feel heat where it wasn't supposed to be. The cell would be shorting internally as I said above and just keep getting hotter and hotter until it finally fully discharged to 0.00 The really bad thing is that unless you keep checking for Heat it is very hard to find the cell that is running away on discharge as there is no visual indication. Makes for some hurried unsoldering to get that bad cell out of the pack.

I suspect that this is one of the main causes of fire in recycled laptop cell battery packs. It also doesn't always show up right away. I had one case where the battery pack had been assembled, and I was balance charging the pack when I got a low balance port shutdown. When I picked up the pack I burned my finger on the internally shorted cell which had failed during the second charge/discharge cycle. In every case where I have had a cell failure during balance charging (two cells on one pack at the same time it has also caused overcharging of the remaining cells. Twice I have had to throw out a fell 10 cell pack because of the internal shorting of cells causing the remaining cells to charge higher than 4.3 volts. In one case it charged the other 8 cells to 4.53 volts and left two at O volts. Luckily I was keeping close tabs on this charge as I was trying out Parallel charging for the first time. Not gonna do that again.

this is the problem with bulk charging the lipo. sometimes a cell will just short out and drop to zero V and produce heat as it shorts and then the adjacent cells get overcharged at the same time. perfect recipe for thermal runaway to start.