LiPo Balance Plug

Having nothing better to do as it had started raining, I checked out my 3s and 4s LiPos ready for the next flying session. The 4s batteries checked out OK, but one of the 3s group didn't. Funny because it was the only Overlander. Checking each cell individually I kept getting inconsistent results with the third cell. Rather disappointing as the Overlander is a year younger than the Zippy compacts. I had a close look at the balance plug and saw that the terminal to the affected cell wasn't bright and shiny like the other three. I popped the terminal out of the housing and it looked distinctly sad, it was a dark brown colour. I wondered if it could be black wire corrosion, but stripping the insulation close to the terminal showed bright clean wire. I crimped a new terminal to a spare piece of wire, cut off the wire from the battery and soldered on the new piece. With the balance plug reassembled, the battery checker was showing a stable reading, but I think the battery has probably got to an irretrievable state. When it stops raining, I'll see if it'll take a low rate balance charge, after all, you never know.

Hi Brian

A major indicator of cell condition is internal internal resistance so suggest investigate if your charger can read INT RES . The following figures represent my batteries tested by my charger so use as reference only. Personally i think the more realistic readings are obtained by those chargers which do his test during charge / discharge ie a dynamic test as opposed to some chargers which do a static test. If it cant, there are many electric fliers at WMAC who could test them for you.

Typically on a 2200mA pack = 3 to 4 milliohms per cell for a new battery. At 10millohms they are usable but getting tired
on larger the cell capacities of 4000mA i except to see 1.5 to 2 mill ohms on a good quality new battery and have rejected new batteries with readings > 6 millohms

Thanks Kevin, I haven't checked the internal resistance between cells, but the Overlander battery accepted a charge after the balance plug was fixed.
It didn't finish charging until late last night, a quick check on the capacity meter gave 98% on all cells. I'll go and browse the charger's handbook, I think the B6 has the internal resistance facility.