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battery question

Old 01-25-2007, 11:20 PM
  #1  
supra guy
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Default battery question

Ok I recentely got two 8.4V 600mAh Ni-MH battery packs from my friend to replace my old ones. Anyway, I charged one of them up today and put it into my parkzone J3 cub and headed off to the flying field. The takeoff was an uneventful hand launch and I proceeded to assert my aerial dominance over this otherwise unused field (lol ) anyway, every thing was all good until my motor stopped, I was able to do a rough landing which ended in my plane upside down on the ground, no damage though. So I picked it up and tried to start the motor, it spun for like five seconds then stopped, although I still had full control of my control services. What happend seemed to be similar to the battery dying, yet I had only been flying for maybe a minute minute and a half. Now according to my friend, he charged up both batteries about a year ago, used most of the charge on one, none of the other. He finally fully discharged them about two months later (don't ask about this weirdness, I don't know either :| ) anyway, since then they hadn't been used, I figured they'd be fine but now I'm wondering if the weird charging and discharging past of these batteries could of had an effect on what happend, or if I charge them a few more times if they'll be fine.

Sorry for the long post, thanks in advance.
Old 01-26-2007, 12:45 PM
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bluestratos
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Default RE: battery question

I would cycle the batteries a few times with a good digital charge/discharge charger. If you dont have one you can buy them starting around $100. If after a few cycles you are not getting charge readings within 10% of the pack capacity, say about 540 or better the batteries should be replaced. The BEC circuit in you speed control sensed that the batteries were low and cut off power to the motor to preserve enough power to power the servos. NMHD are good but in electrics Lipos are much better as you can get a lot more capacity for the same physical size. 600 is pretty small evey for a very small electric motor. I have a Funtana electric that I fly with 1100 lipos and I get a solid 15mins of flying time. If I just cruise around I have pushed that to 25 mins.
A warning though.. although new technolgy is making lips safer, for the most part they are still very subject to bursting into flames if they are not charged correctly or are damaged, say in a crash so be sure to charge in a safe place under supervision and only with a charger that clearly states it will charge Lipos.

Best regards,
Randy
Old 01-26-2007, 03:23 PM
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2slow2matter
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Default RE: battery question

No way you can expect NiMH or NiCd batteries to hold any appreciable charge over a period of 10 months without re-charging. If they are used or not.
I would cycle them, but guess they are probably toast. . They've been mistreated.
Old 01-26-2007, 09:25 PM
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supra guy
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Default RE: battery question

thanks guys, I might just replace them, I had a rather evil idea of buying new batteries than taking the messed up ones back in the new ones packages haha. Anyway, thanks again.
Old 01-27-2007, 08:38 AM
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Rodney
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Default RE: battery question

As a last resort befor pitching them, check out the following thread and try it out. http://members.aol.com/davthacker/balancecharging.htm

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