Jun 17, 2012, 10:03 PM Registered User Joined Dec 2011 46 Posts 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
 Jun 18, 2012, 12:12 AM Crash and learn United States, PA Joined Dec 2011 2,689 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 Last edited by Ribble; Jun 18, 2012 at 12:29 AM.
 Jun 18, 2012, 02:31 AM Registered User Letchworth, Great Britain (UK) Joined Jul 2004 12,814 Posts 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.
 Jun 18, 2012, 10:02 AM Cranky old fart Germantown, WI. Joined Oct 2007 21,539 Posts 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.
 Jun 18, 2012, 12:16 PM Registered User United States, OR, Canby Joined Aug 2011 2,710 Posts How about this LiFepo4? http://www.batteryspace.com/lifepo41...olyswitch.aspx
 Jun 18, 2012, 12:25 PM Cranky old fart Germantown, WI. Joined Oct 2007 21,539 Posts 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.
 Jun 18, 2012, 04:33 PM Registered User United Kingdom, England, Liverpool Joined Mar 2009 1,654 Posts 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.
 Jun 18, 2012, 05:28 PM Cranky old fart Germantown, WI. Joined Oct 2007 21,539 Posts The HBFP V2 used 3S batteries as standard. It realy made a difference in performance.
 Jun 19, 2012, 06:59 AM Registered User United Kingdom, England, Liverpool Joined Mar 2009 1,654 Posts 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.