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Old Jul 09, 2006, 04:07 PM
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Montag DP's Avatar
United States, GA, Atlanta
Joined Apr 2005
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Help!
Vampower battery problem

I recently bought a Vampower 1700 mah 3S pack, along with the LiP BalM balancer. I charged the battery and balanced it, and it worked fine for five flights. After five flights, I balanced it again according to the instructions that came with the balancer. It kept balancing for hours, which I thought was okay because the instructions also said that new packs may take a long time to balance. After three or four hours, it was still not done, so I left the balancer going and went to bed. When I woke up the next morning, the balancing lights were off. However, the battery would not charge anymore with my Apache 1S-4S lipoly charger. I get the blinking error light every time I try to charge it now.

Is there anything I am doing wrong? The only thing I could think of is that maybe the balancer discharged the cells too low? That seems very unlikely to me, especially since the voltage of the cells jumps back up after load is removed. For the record, I tried charging and balancing at the same time before I went to bed, but I still got the blinking red charge light signifying a charge error. At the time I figured for some reason my charger had trouble recognizing the battery pack while I was balancing, but it didn't work later either without the balancer attached. I have not discharged the cells too low. The fifth flight was no longer than any of the other flights, and there is no sign of swelling either. It seems that my charger just cannot recognize the battery anymore. I have charged other batteries successfully since this time.

Did I just get a dud, or did I do something wrong? What can I do to make my chrager recognize the cells again, and should I balance differently in the future?

Dan
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Old Jul 09, 2006, 07:30 PM
ParkFlyer
xFxLxYxExR's Avatar
Joined Nov 2005
754 Posts
Dont leav your batterys unatended, ever. lol that was a stupid thing to do. What if your pack was to catch fire while you were sleeping and your you get killed while asleep? Dont go to bed inless everything is off and everyhting is unpluged. Now I dont mean to stare at the pack whole charging or anything, im just saying atleast be awake. Now as for the problem, if you can try to charge it on your friends charger or try a different charger if possible...also have you checked the voltage? Without of wattmeter your walking blind in a room full of poisines snakes....
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Old Jul 09, 2006, 07:46 PM
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Montag DP's Avatar
United States, GA, Atlanta
Joined Apr 2005
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Well I don't think it was going to blow up while balancing. Take note it wasn't connected to the charger at the same time. Correct me if I'm wrong.

I don't have another charger or a friend's charger to use. I know I need to get a wattmeter, I was just wondering if there was anything I could do about it now. Honestly, if the pack had been discharged too much I don't think that would have caused the charger to not recognize it. I will get a wattmeter as soon as I get a chance, but I don't really think it would help me that much in this situation. Thanks for the input though. In the future, should I start balancing while I charge or even wait until the pack is done charging?
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Old Jul 09, 2006, 07:55 PM
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United States, CA, Bear Valley Springs
Joined Feb 2000
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If the pack voltage is too low the charger indeed may not recognize it. Find a slow charger of some kind and slowly bring the voltage back up watching it very carefully and taking voltage readings along the way. Once it reaches 3 volts/cell the charger should recognize it.

mw.
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Old Jul 09, 2006, 08:20 PM
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Montag DP's Avatar
United States, GA, Atlanta
Joined Apr 2005
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Thanks, I will try to do that. I just read the Vampower balancer thread and the manufacturer recommends balancing after charging. I guess I got that wrong. Anyway, do you really think the balancer could discharge the battery that much? I am quite sure I didn't over-discharge during flight.

One more question, what voltage should I use to slowly bring the pack up?
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Old Jul 09, 2006, 08:50 PM
swede
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United States, UT, Vineyard
Joined Aug 2005
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Will LiPo's still take a charge if they were discharged too low? I had a LiPo that was left attached to a plane (ESC had a power switch to turn everything off) and evidently the power switch didn't turn it all off. I went to top off the pack a week later and the cells were down to 1.5 volts. My Apache charger did the same thing as Montag DP's did. I just figured the battery was a loss.
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Old Jul 10, 2006, 01:30 AM
Vic and Quinn Walton
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Santa Barbara CA
Joined Jan 2006
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generally the power switch on esc only turn off the BEC so that the reciever does not get power but they keep power going into the motor so that if you leave a battery connected it will be drained
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Old Jul 10, 2006, 08:21 AM
swede
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Yeah, I found that out the hard way. Bummer of a deal.
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Old Jul 10, 2006, 09:08 AM
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yes, the balancer will keep right on trying to exactly balance a pack which means each cell gets a tiny discharge depending on it's state compared to the other cells. the balancer keeps going from cell to cell as long as it's connected to the pack. that's what the lights tell you as they blink.
I think twelve volts would be sufficient to bring the pack back up.

mw
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Old Jul 10, 2006, 09:44 AM
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Montag DP's Avatar
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Thanks a lot. I'll see what I can do.

Dan
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Old Jul 10, 2006, 01:28 PM
Registered User
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Joined Apr 2005
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A NiMH charger can bring a lipo pack up to the point where your lipo charger will pick it up; set it on 250-300 mA and charge for maybe a minute at a time. If you don't have a multimeter to check pack voltage, take it off the NiMH charger and put it on the lipo charger and see if it'll pick it up. If it doesn't then charge another minute on the NiMH and try it again. Whatever you do, DON'T leave the pack unattended while on a NiMH charger and DON'T try to charge to capacity! Since you say you don't have another charger, you can probably find somebody to help you out with this at your local field or at a hobby shop.
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Old Jul 10, 2006, 01:28 PM
Über Geek
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Quote:
Originally Posted by denial15
Will LiPo's still take a charge if they were discharged too low? I had a LiPo that was left attached to a plane (ESC had a power switch to turn everything off) and evidently the power switch didn't turn it all off. I went to top off the pack a week later and the cells were down to 1.5 volts. My Apache charger did the same thing as Montag DP's did. I just figured the battery was a loss.
Sometimes yes, sometimes no. Montag has a 50/50 chance of reviving his kaput battery. The other 50% is blowing it up. Montag, be careful. When you over-discharge a lipo (even just one cell) charging it back up is a risky thing, and almost invariably there will be pack damage at the least. Worst case is a fire/explosion/etc - you know the rest.

Just as a FYI, *all* seperate cell balancers I've encountered have balanced cells by *discharging*. So, yes, if you leave a non-charged pack on one overnight, it'll over-discharge the cells. I think some of the more expensive balancers watch to make sure they don't drop the cell voltage too much, but some of the less expensive ones just seem to discharge to balance (and the cells will never be PERFECTLY in balance, so it'll discharge continuously). It's normally not a big deal, because it's a very slow discharge, but if you leave it overnight on an already close-to-empty pack, it could very easily take it below the margin of safety for lipo cells.

David
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Old Jul 11, 2006, 08:20 AM
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Montag DP's Avatar
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Well, thanks for the responses guys. I hooked it up to a 450 ma slow chrager, which was the only one I could find, for about a minute. After that the lipo charger recognized it. I have it slow charging on the lipo charger right now. Still no sign of puffing or anything unusual. I just wish they'd say in the instructions to balance only while charging or afterwards. Now I have to hope the battery works and doesn't blow up or something... I'll have to see.

Dan
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Old Jul 11, 2006, 09:07 AM
Southern Pride
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http://www.rcgroups.com/forums/showp...39&postcount=1


My mini review

http://www.rcgroups.com/forums/showp...0&postcount=11



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Old Jul 11, 2006, 10:10 AM
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Montag DP's Avatar
United States, GA, Atlanta
Joined Apr 2005
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Yeah, thanks Charles. I actually saw those posts, just too late. I'll report on the battery after it's done charging and I try it out again in my helicopter.
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