Imbalance over 0.04V means a cell is going to fail???  
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All Forums >> Electric Aircraft Universe >> Electric Pattern Aircraft >> Imbalance over 0.04V means a cell is going to fail???
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Imbalance over 0.04V means a cell is going to fail??? - 4/2/2007 2:08:34 AM   
xalm04



Posts: 77
Joined: 9/13/2004
From: Quito, ECUADOR
Status: offline 		Hi, I have a TP 4200 10 cell battery that works fine as I can do a complete P07 with normal power, however one cell is dropping almost 0.040 V more than the rest and when charging it reaches 4.224 V while the rest are at 4.209, so my guess is if that particular cell is going to failure. I always charge this 10cell pack with 1010 C TP charger and TP210 balancer connected. Do anyone know what this could mean? Is there any method to "return" to its normal behaviour? Thanks

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Xavier Almeida
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RE: Imbalance over 0.04V means a cell is going to fail??? - 4/2/2007 9:19:09 AM   
Malcolm H



Posts: 276
Joined: 10/24/2002
From: glasgow, UNITED KINGDOM
Status: online 		Xavier,

It looks like this one cell has less capacity than the rest. That is the reason why it drops to a lower voltage quicker than the other cells and is also the reason it gets full while the other continue to accept current.

If this is a relatively new pack, say less than 20 cycles I would return it to Thunderpower who will probably repair it by changing the cell. If it has done quite a lot of cycles then it won't be worth repairing as other cells will start to lose capacity soon.

All you can do in these circumstances is make sure that you don't discharge the pack too low. A few minutes after flight the low capacity cell should bounce back to 3.7V minimum.

Hope this helps.

Malcolm

(in reply to xalm04)
       Post #: 2

RE: Imbalance over 0.04V means a cell is going to fail??? - 4/3/2007 1:43:05 AM   
xalm04



Posts: 77
Joined: 9/13/2004
From: Quito, ECUADOR
Status: offline 		Thanks Malcom. This package has 95 cycles, so I think I´ll try to get the most of it before it dies. I´m buying another 5cell pack to replace the one half and hopefully it will last for another 95 cycles. Do you know is it is possible to repair these batteries, replacing a bad cell?

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Xavier Almeida

(in reply to Malcolm H)
       Post #: 3

RE: Imbalance over 0.04V means a cell is going to fail??? - 4/3/2007 8:59:39 AM   
Malcolm H



Posts: 276
Joined: 10/24/2002
From: glasgow, UNITED KINGDOM
Status: online 		Xavier,

As I said in my last post it is possible to change a cell but it isn't easy to do unless you are very confident in your soldering and some cells have aluminium tabs which requires special solder. Also due to differences in cell capacity between new cells and those with several cycles you are unlikely to end up with a good pack. I'm afraid for the same reason mating a new 5S pack to an old one is also not a good idea. You will soon end up with imbalance between two halves of the pack. I suggest you carefully use the existing 10S pack until you can replace it with a complete new 10S.

Hope this helps.

Malcolm

(in reply to xalm04)
       Post #: 4

RE: Imbalance over 0.04V means a cell is going to fail??? - 4/3/2007 1:14:17 PM   
patternrules


 

Posts: 548
Joined: 7/28/2002
From: Nineveh, IN, USA
Status: offline 		How much have you been putting back in after your flights?
First I would leave the balancer hooked up to and let it run, if voltage gets down to 41.50 volts and recharge, may have to do a few times if your using TP 1010 and 210 balancer.
Send it in postage is cheap and see what they say if it doesn't come back into balance. Thunderpower has been very good, may even offer you a good deal on a replacement. Let them know how much Thunderpower stuff you have.
Steve Maxwell

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Steve Maxwell

(in reply to Malcolm H)
       Post #: 5

RE: Imbalance over 0.04V means a cell is going to fail??? - 4/4/2007 7:05:47 AM   
Malcolm H



Posts: 276
Joined: 10/24/2002
From: glasgow, UNITED KINGDOM
Status: online 		Yes I would agree, Thunderpower aftersales service has been excellent even to here in the UK.

Malcolm

(in reply to patternrules)
       Post #: 6

RE: Imbalance over 0.04V means a cell is going to fail??? - 4/4/2007 3:11:12 PM   
xalm04



Posts: 77
Joined: 9/13/2004
From: Quito, ECUADOR
Status: offline 		I have been putting from 2900 mAh to 3200 mAh. After this weekend I was doing exactly what Steve says, and after a couple of balance-recharge cycles it is now balanced at 0.005 V at full charge. I'll fly with it and see what happens to the cell. In the worst case I'll have to do this every week to protect the low voltalge cell and try to get the most from this package, hopefully at least 40 more cycles.

_____________________________

Xavier Almeida

(in reply to patternrules)
       Post #: 7

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