Haiyin pack possible bad cell

[trillian]

I have a pair of Haiyin 4000mah packs that I had not flown in about 2 months and were on a storage charge. I flew them on Monday and one cell dropped down to 3.76 volts and does not appear to be coming up. The rest were only down to about 3.9 ish so it was definitely not flown too long or hard.

My Hyperion charger was trying to balance it for literally hours and that one cell won't budge.

I'm going to have to leave it because I am out of town from tomorrow till the 17th of May.

Anyway, does it sound like just a cell has gone bad or is there something I can try when I return that might revive it?

[chrisleematt21]

Sounds like a bad cell. I think with lipos once they are gone there gone.

[Grumpy]

Often, if your charger doesn't have very high ballance drain current, then it will fail to balance cells that are very far out of balance. You dont say what model of charger you have but some Hyperion chargers have very poor balance drain current rating, so this could well be it.

You could use a better charger (Powerlab or iCharger Duos have good balance drain capability) or you could use a stand alone cell balancer to bring down the other cells to match the low one, then re-charge as normal. Alternatively you can tap into the balance plug and charge only the single cell as a 1s LiPo to bring it up to full charge.

Do any of this with caution and watch out for the cell puffing because it could just be bad, in which case the battery is toast.

[smsodhi]

In these situations, I have plugged the suspect battery into a balance board, then a good one which is of similar charge. I just plug in the main leads first to allow the current to flow between the batteries. Then I plug in the balance leads. This normalises the cell V across all cells and will bring up the cell with the low voltage.
Then charge it and observe the cell.
Hope you have a good trip.

[trillian]

Thanks everyone for all the suggestions. I didn't have time to mess with it before I left but have been working with it today. The first thing I tried was using a standalone balancer and after a while the balancer (this is a Robotbirds checker/balancer) started beeping and it showed one cell down to 2.23 volts!

So I thought OK I'll try my regular Hyperion charger again only this time do a full charge whereas before I was doing a storage charge. Sooooo, when I connected it the cell that seemed to be bad was showing 4.2 volts! I now suspect that it may have been just one balance wire making a poor connection. We shall see, if I'm lucky it's actually OK, if not then it's 50 quid for a new pack. The charger seems happy with it and all cells read good voltage, the proof will be in how it performs under a load.

[Planehazza]

I've had this exact thing happen on a Haiyin that I bought about 2 years ago. Chris at Electriflyer replaced it with no hassle.

[barryorbik]

I bought two Haiyin 3S 2650 packs at Weston park to use in series in my Gaui 550 and although they have only done eight flights in total and have always been balance charged at 1C and stored at 3.8 Volts when not in use but one pack now has a cell at 0.8 Volts. When I contacted Electrifier the initial response was not positive but eventually Paul offered me 50% off a replacement pack, so a result of sorts.

[Planehazza]

I bought two Haiyin 3S 2650 packs at Weston park to use in series in my Gaui 550 and although they have only done eight flights in total and have always been balance charged at 1C and stored at 3.8 Volts when not in use but one pack now has a cell at 0.8 Volts. When I contacted Electrifier the initial response was not positive but eventually Paul offered me 50% off a replacement pack, so a result of sorts.

Shame that like. Chris was spot on every time I spoke with him.