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Old Jun 17, 2012, 10:03 PM
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Joined Dec 2011
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Help!
8.4v NiMh conversion to Lipo

Hey Guys and Gals,

I was given a Jabo 2 electric Heli, however the NiMh battery packs are dead and won't charge.

I want to switch to LiPo which would be easier than making new packs.

However I can not find one that has the same voltage, the packs for the Heli are 8.4v 800mah or7x AAA 1.2v batteries.

What could I use to replace the NiMh, 7.4v Lipo?

Any help would be great.

Thanks
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Old Jun 18, 2012, 12:12 AM
Crash and learn
United States, PA
Joined Dec 2011
1,605 Posts
NiMh 8.4v 800mah or7x AAA 1.2v batteries has a voltage range of roughly 7.0v to 9.8v.

LiPo's
Two 3.7v cells = 7.4v -- voltage range roughly 7.0v to 8.4v
Three 3.7v cells = 11.1v -- voltage range roughly 10.5v to 12.6v

So, a two cell 7.4v LiPo would work. You would have to be careful not to fly it below 6.0v and buy a LiPo battery charger. Using the NiMh charger would be dangerous (fire hazard) and likely ruin the LiPo battery.

If it were me, I would build a NiMh 7 cell battery pack from AAA cells which would be the correct physical size with perhaps higher mah ratings for longer flight time.


Understanding RC LiPo Batteries
http://www.rchelicopterfun.com/rc-lipo-batteries.html
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Last edited by Ribble; Jun 18, 2012 at 12:29 AM.
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Old Jun 18, 2012, 02:31 AM
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Letchworth, Great Britain (UK)
Joined Jul 2004
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A 2S (7.4v nominal) 800mAh LiPo pack would be much lighter than seven AAA cells, which I think would compensate for the slightly reduced voltage.

But I think the hazards outlined by Ribble outweigh the advantage.
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Old Jun 18, 2012, 10:02 AM
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Germantown, WI.
Joined Oct 2007
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I think they stopped making this heli in 2005. It's a copy of the original Hummingbird FP heli. Parts will be very difficult to find. So you best make sure you have all the parts and the crystals for the transmitter and receiver before getting too involved. If you are sure you have everything, a 7.4v 800mah battery is your best choice. These helis had very marginal motors for the mass they had to lift and this size lipo weighs a lot less than a comparable nimh battery.

It was standard procedure to replace the the 8.4v nimh battery with a 7.4 lipo on all of the old Hiller head 300 size FP helis that used this same design (Hummingbird, Jabo, Walkera 4#, HBFP, etc.). The practice was so common the manufacturers even started doing it as an "upgrade". So, you know you got the real old one, if you got the nimh version.
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Old Jun 18, 2012, 12:16 PM
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United States, OR, Canby
Joined Aug 2011
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How about this LiFepo4?

http://www.batteryspace.com/lifepo41...olyswitch.aspx
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Old Jun 18, 2012, 12:25 PM
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Germantown, WI.
Joined Oct 2007
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I would be very careful about increasing voltage. The boards on many of those helis were marginal and it didn't take much extra load to burn out FETs.
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Old Jun 18, 2012, 04:33 PM
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United Kingdom, England, Liverpool
Joined Mar 2009
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my friend has donated to me a HBFP1 variation, but there are so many different parts on it, I don't know what the helicopter actually is, it is partly HBFP1, partly the V2, but it also has the old IMH battery tray style. I am actually running a 3 cell but I it is known that the Esky 4in1 can take this, I am not sure about other variations. All I know is my 4in1 is an Esky 35mhz, so I imagine you can risk a 2 cell surely.

Yeah - I don't know how long mine will last on a 3 cell, I wouldn't recommend it on yours it might not be able to take the voltage. Lol.

(Good to see people still try and attempt to fly these retro-birds, other than just me.
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Old Jun 18, 2012, 05:28 PM
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The HBFP V2 used 3S batteries as standard. It realy made a difference in performance.
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Old Jun 19, 2012, 06:59 AM
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Yeah, I know, I don't know what this 4in1 is from but it is taking 3s nicely, and is flying much better on the advanced swashplate settings.
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