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LiIon, LiPo, NiCd & NiMh General General Battery Support


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Old 06-22-2008, 06:45 PM   #1 (permalink)
 
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Default Reviving a lipo...

Hi guys, I have 2 E-Flite 7.4v 800mAh 2-cell Li-Po batteries and they seem to not be able to take a charge. I do not want to buy a new charger or a new battery because of money problems(trying to save up for a 400) I do not have a good computer charger as I am using the stock E-Flite charger. I can get at least maybe a minute charge of flight time out of them before they can make my CX barely hover. Is there anything I can do to revive the Li-Po battery without buying a new charger? BTW, I have a NiCd Tower hobbies charger if that would be able to do any good... I am going to check the cell balance when I get access to a Volt meter. Help would be appreciated...
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Old 06-23-2008, 09:13 AM   #2 (permalink)
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Nobody can help me??!?!
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Old 06-23-2008, 12:30 PM   #3 (permalink)
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unfortunately those batteries are finished. they've developed high internal resistance and it's not that they can't take a charge, rather that they cannot output the current needed to fly your cx. the eflite ones do not last very long IMHO.

definately DO NOT charge them on your NIMH charger.........a definite NO NO!

throw them away and get some new ones.
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Old 06-23-2008, 04:16 PM   #4 (permalink)
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Adding my voice to the chorus: If the LiPo won't take a full charge, discharge it to empty and chuck it. I normally slice off the balance leads and the discharge lead. The wiring and connector are useful.

The E-Flite Blade CX cells (E-Flite 800mAh 2S) are total crap. They advertise them as "10C"... yeah, if you fly them at 8 amps (10C), your total number of cycles will number less than three dozen, guaranteed. Fly them as 6C cells (4.8A max discharge) and their longevity is just fine. They are really 6C LiPos.

The Blade CX pulls 8A peaks. The only way I got E-Flite's batteries to last for more than 50 cycles was to wire a parallel cable and balance the amp load across two batteries at the same time. They lasted for about 70 cycles each that way, and bonus: I doubled my flight time

For the nay-sayers, I live at around 5000 feet elevation, which requires substantially more throttle than sea level on a Blade CX. The batteries are really marginal on cycle life discharging more than 5A sustained. Parallel them up and treat them as 6C batteries, and they are fine. Or else use them in a 4A peak-discharge setup, like a light flying wing or something.

I also like many other E-Flite products. It's just their vendor for their 800mAh 2S batteries isn't doing the job right for a 10C discharge, IMHO. I've seen a ton of CX helis fly, and everybody at this altitude has the longevity problem. Gang them in a pair in parallel, and the batteries last more than twice as long, even though you have to hold higher throttle to deal with the extra weight.

Or, better yet, buy a battery that's actually 8C+ discharge, costs half as much, and has great cycle longevity: http://www.commonsenserc.com/product...products_id=58 . Not trying to be a shill for CSRC, but those boys rate their packs truthfully. Most other vendors would call CSRC's 8C packs 12C packs, and their 15C packs 18-20C packs.
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Old 06-24-2008, 10:07 AM   #5 (permalink)
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stock eflight charger is JUNK
I had similar but not as bad issues with my CX2 batteries. Low flight times at about 2-3 minutes. 1st charge on my new then Cellpro 4s and I was at 5mins. 2nd charge I think it was about almost 7mins. Couldn't believe it. May help you, may not. but that charger from eflight is HORRIBLE, and my Blade 400 eflight charger suxed too.
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Old 06-25-2008, 03:17 AM   #6 (permalink)
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i am happy with these batts. better battery at a better price.
http://www.helidirect.com/product_in...oducts_id=2108

and they work ok with the stock charger.
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