Diamond label 6s 5000 1 cell high IR

[-G's]

One of my Diamond label 6s 5000s cell #6 IR is 10+ m-ohms. Bought this pack second hand (1 of 4) fairly new <100 cycles total to date. Pack will balance eventually, but takes FOREVER. Can this cell be rehabbed in any way or is it li-toast?

[Gregor99]

If the cell has degrade, it cannot be revived. Just to be sure, here are some quick questions. After the flight, what are the cell voltages? During the charge what is the behavior of the suspect cell? Does it reach 4.2v much faster than the other cells, or does it lag behind? What charger is being used?

[-G's]

Originally Posted by Gregor99

If the cell has degrade, it cannot be revived. Just to be sure, here are some quick questions. After the flight, what are the cell voltages? During the charge what is the behavior of the suspect cell? Does it reach 4.2v much faster than the other cells, or does it lag behind? What charger is being used?

Charged it yesterday and didn't get to flying it until 4 hours later. It had been suspect after charging last weekend so I checked it before installing in heli to find a .218 volt difference between cell 6 and 4. I usually charge in parallel using a PL8, but used a 4010 duo to top off/ rebalance. Cell 6 lagged far behind and took about an hour to balance. I hovered the battery as part of a 12s setup for 4 mins and rechecked. Cell 6 was 3.7v and other cells were 3.9v.

[Mercuriell]

Have a good look at the balance lead and plugs, a bad joint here could give a falsely high IR

[Gregor99]

Originally Posted by -G's

Charged it yesterday and didn't get to flying it until 4 hours later. It had been suspect after charging last weekend so I checked it before installing in heli to find a .218 volt difference between cell 6 and 4. I usually charge in parallel using a PL8, but used a 4010 duo to top off/ rebalance. Cell 6 lagged far behind and took about an hour to balance. I hovered the battery as part of a 12s setup for 4 mins and rechecked. Cell 6 was 3.7v and other cells were 3.9v.

If I understand you correctly the pack was charged to 4.2v per cell on the Powerlab8. It rested for 4 hours and cell #6 was below 4v while the other cells were closer to 4.2v. Then the pack was balanced on the 4010. Presumably leaving cell #6 at 4.2v shortly before the charge. After the flight, cell #6 was 200mv below the other cells. Correct?

If that sequence is correct, it sounds like cell #6 is experiencing a high rate of self discharge. This can occur due to an internal short in the cell. The cause of the internal short is often due to focused pressure on the exterior of the cell. This can happen due to mishandling, bumping the pack during installation, tight Velcro strap,etc. It can also be caused by a mfg detect.

If this is really what's going on with the cell, then I would be careful with this pack. The short can expand, resulting in more serious damage, often during charging. Because voltage readings can vary between devices, I would confirm the self discharge with a DVM before disposing the pack. I would not charge the pack until pack is checked with a DVM.

[-G's]

The pack does have exterior damage on one corner. Can the pack be repaired or made into a 5s?

[Gregor99]

A used pack of unknown history, I would not bother with it. Just too risky. But I know some modelers swap out bad cells or remove a bad cell from pack. So it can be done. It's risky and requires that you remove the heatshrink and work on the bare contacts of the cells. Then re-cover the pack with heat shrink. Its easy to make a mistake, cause a short, sparks, etc.