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Forget the %s.... What individual cell voltages is it displaying when the charge cuts off? Are all the cells in balance, or is there one significantly different from the others? It sounds like your pack may have a duff cell and the charger is sensing that, but we need this info to be sure. If you charge another pack using the identical programme, does it reach full charge (4.2V/cell for any std lipo, 4.35V/cell for an HV variant)?

Edited by MattyB
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Wow, those are miles out of balance. If your charger just run it on a balance cycle only (no charge), then once that finishes run a balance charge again and see if all 4 cells get to 4.2V again. My suspicion though is that the pack is probably not long for this life...

 

How many cycles does it have on it, and what kind of C ratings do you discharge it at? Has it ever been discharged below 3V/cell?

Edited by MattyB
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OK, so this is a brand new pack? Never charge a pack without checking the cell voltages, as most suppliers will not take it back once it has been charged as they have no idea how it has been treated. 

 

Re: balancing, most chargers can run a straight balance cycle - what charger do you have?

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2 minutes ago, Diamond Geezer said:

How do i run a balance charge cycle if I connect the battery by balance lead only it says no battery connected 

 

You'll want the main connector put on.

 

I would expect a "charge" mode as well as "balance charge" - you want the latter.

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5 hours ago, MattyB said:

Forget the %s.... What individual cell voltages is it displaying when the charge cuts off? Are all the cells in balance, or is there one significantly different from the others? It sounds like your pack may have a duff cell and the charger is sensing that, but we need this info to be sure. If you charge another pack using the identical programme, does it reach full charge (4.2V/cell for any std lipo, 4.35V/cell for an HV variant)?

That's some of the best advice I've ever seen posted on the topic ? - the % read out is halfway to chocolate teapot territory IMO. The individual cell voltage is what needs checking, I check mine before and after nearly every flight to see how much they have been discharged and what the balance is like. My meter doesn't show percentages.

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3 hours ago, Diamond Geezer said:

Matt

the charge don’t cut off it just keeps going all the time it was on charge for a good few hours yesterday went up by 1%the cells are 

This would be typical of a battery well out of balance - it can take many hours.

 

As one cell has reached 4.2v the charger will continue to float a charge voltage across the pack to charge the other cells while continuously terminating the charge and loading the high cell to keep it from exceeding its safe voltage. This is a very slow process…
 

You do need to consider that the battery is probably faulty though - it shouldn’t have ever got this far out unless you have habitually charged without using a balance charge facility. 

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If that was my LiPo, I'd have long ago recognised that it was duff - dangerous in itself let alone unreliable for use in a heavy flying object costing a lot more than a single battery - and for the sake of a few quid I'd have immediately discharged it entirely for disposal and purchased a new one.

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