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One LiPo cell won't charge

kkelly

New member
#1
I'm new to electric flight and all the nuances of LiPo batteries. I have a 3S with maybe a dozen cycles on it. After the last time I used it I brought it back up to storage charge without issue. Now one cell won't take a charge at all. The charger gives up with an error that I think means that cell isn't increasing in voltage ("BALANC DLTA V", which isn't discussed in the manual). That cell does show up when I connect the battery to a tester, so I don't think there's a broken connection on the balance leads. Is the battery toast or is there something I could try that may get that cell working again?
 

kpixels

Antigravity or bust...
#2
If you have a connector board, the kind that lets you charge multiple batteries together, then you might as well try this. Plug a fully charged battery then carefully add your questionable battery (no charger). If the cell is still good they should even out enough to bring the cell up to a high enough voltage to make the charger happy. Charge each battery individually afterwards to restore cell balance.
 

Hai-Lee

Old and Bold RC PILOT
#3
You may find that "BALANC DLTA V" means "Balance Delta Voltage" which means the charger is signalling that the balance of the cells is such that one cell does not have the same, or near the same, voltage as the others.

Some balance chargers do not like cells that are too far different. A different charger or charging the "Low" cell separately MIGHT help!

Have fun!
 

kkelly

New member
#4
If you have a connector board, the kind that lets you charge multiple batteries together, then you might as well try this. Plug a fully charged battery then carefully add your questionable battery (no charger). If the cell is still good they should even out enough to bring the cell up to a high enough voltage to make the charger happy. Charge each battery individually afterwards to restore cell balance.
Hi. Thank you for the idea. I don't have one of those. I found something suggesting charging the battery at very low amperage. I tried and now I have a new problem: the charger said the balance connector was connected incorrectly. I confirmed it's plugged in the right way (my balance board pretty much makes it impossible to do otherwise). The charger still accepts other batteries, and it will show a voltage for every cell so I know there aren't any wiring issues.
 

evranch

Active member
#5
What is the voltage of the damaged cell when you measure it with your tester? Before you do anything to it, you should make sure it's not dangerously discharged.

Delta V likely means that whatever means of balancing the charger uses is not capable of compensating for the amount of imbalance. You still may be able to balance it manually, by connecting jumpers to the balance connector and charging the cells individually.

Another trick, if a cell has been slightly overdischarged to the point where the charger refuses to charge it, you can trick the charger by setting it to a different chemistry for a short time. Charging the entire pack gently as if it was a NiCd pack, for example, while monitoring it closely. Once it recovers into the acceptable range, you can charge it as a regular battery again. Watch very closely that you do not take any of the other cells above 4.2V, though.
 

kkelly

New member
#6
You may find that "BALANC DLTA V" means "Balance Delta Voltage" which means the charger is signalling that the balance of the cells is such that one cell does not have the same, or near the same, voltage as the others.

Some balance chargers do not like cells that are too far different. A different charger or charging the "Low" cell separately MIGHT help!

Have fun!
It hadn't occurred to me that the charger might be giving up without trying because of that. I figured it would just bring the low cell up first then charge them all. I just have the one charger. It doesn't seem to have a way to charge one cell. I tried running the discharge program, hoping it would bring the other cells down to the same voltage as the wonky one, but it gave me the same delta V error. Argh.
 

kkelly

New member
#7
What is the voltage of the damaged cell when you measure it with your tester? Before you do anything to it, you should make sure it's not dangerously discharged.

Delta V likely means that whatever means of balancing the charger uses is not capable of compensating for the amount of imbalance. You still may be able to balance it manually, by connecting jumpers to the balance connector and charging the cells individually.

Another trick, if a cell has been slightly overdischarged to the point where the charger refuses to charge it, you can trick the charger by setting it to a different chemistry for a short time. Charging the entire pack gently as if it was a NiCd pack, for example, while monitoring it closely. Once it recovers into the acceptable range, you can charge it as a regular battery again. Watch very closely that you do not take any of the other cells above 4.2V, though.
The cell voltages are:

1: 3.663
2: 3.866
3: 3.861
 

evranch

Active member
#8
What brand is the charger? You should be able to balance out 0.2v with no issues, and the cells are nowhere near overdischarged.

If you have some small solid wire and some jumper leads with alligator clips, you can insert the wires into your balance connector and try to charge up each cell as if it was a 1s. Obviously, being careful not to short them out. Then you can see what happens after your next flight.
 

kpixels

Antigravity or bust...
#10
The cell voltages are:

1: 3.663
2: 3.866
3: 3.861

I like Hai-Lee's idea "charging the "Low" cell separately MIGHT help". Try charging only the low cell as a 1s battery to as close to 3.86V as you can get it. Then charge rest of the way as three cell. Good luck
 
#11
What brand is the charger? You should be able to balance out 0.2v with no issues, and the cells are nowhere near overdischarged.

If you have some small solid wire and some jumper leads with alligator clips, you can insert the wires into your balance connector and try to charge up each cell as if it was a 1s. Obviously, being careful not to short them out. Then you can see what happens after your next flight.
It's a ProTek RC Prodigy 610ez. I'll try charging just the offending cell.
 

Hai-Lee

Old and Bold RC PILOT
#12
The cell voltages are:

1: 3.663
2: 3.866
3: 3.861
There are two ways to achieve cell voltage balance! Either charge the cell with the low voltage or discharge the 2 higher voltage cells.

You might be able to discharge the higher voltage cells using a light globe or similar, (nominally 6 to 12 V and low wattage), just monitor the situation so that you do not over discharge the battery cells because if you do the battery will need to be replaced!

Have fun!
 
#13
I discharged the higher voltage cells down to within .1V of the lower one (they're all around 3.58 - 3.68V now) and tried again without success ("cell connect error" again). On a whim I checked the internal resistance of the pack:

1: 99.9 (max for the meter; also the cell with low voltage)
2: 39.5
3: 19.7

I know those are all quite high. Is there anything else I can try or is it just a bad battery?
 

evranch

Active member
#15
It could be a bad connection as well. If you are confident opening up the end of the battery you can check to see if one of the balance leads has been damaged.
 

IanSR

Active member
#16
Have you tried charging the problem cell as a single 1s lipo through the balance lead? (Connect the particular cell balance leads directly to the +/- of your charger as you do with a single cell). See if it takes charge that way? No need to risk running the charger in nicad mode etc. it'll just think it is charging a single cell not the whole pack.

if you can read the voltage but not charge the cell it does indicate either the wire is compromised or the cell is damaged. Best stick it in a lipo bag before doing anything though, just incase.
 
#17
Have you tried charging the problem cell as a single 1s lipo through the balance lead? (Connect the particular cell balance leads directly to the +/- of your charger as you do with a single cell). See if it takes charge that way? No need to risk running the charger in nicad mode etc. it'll just think it is charging a single cell not the whole pack.

if you can read the voltage but not charge the cell it does indicate either the wire is compromised or the cell is damaged. Best stick it in a lipo bag before doing anything though, just incase.
It took a charge that way but didn't hold it. The charger said the cell was up to 4.1V, but by the time I stopped the charge, disconnected the battery, and connected it to a meter it was back down to 3.8V, and at 3.6V within a few minutes.
 

IanSR

Active member
#18
It took a charge that way but didn't hold it. The charger said the cell was up to 4.1V, but by the time I stopped the charge, disconnected the battery, and connected it to a meter it was back down to 3.8V, and at 3.6V within a few minutes.
Yeah I'm afraid it's dead then, if you're really brave you could take the tape off, remove the bad cell and convert it into a 2s, or bin it, either way that cell is dead.

Also (I know you cannot) don't be tempted to put it in a parallel charger board with a good 3s in the hope of repairing the cell, it won't, all it will do is kill the corresponding cell on the good pack as well.
 
#19
I figured that was the case. Fortunately it's not a big loss. I may try removing the bad cell if I'm bored one day.

Thank you everyone for helping me out with this.
 

mayan

Well-known member
#20
I have a similar problem they cells all balance out good but on flight one cell drops quickier than the others is it dead?