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Futaba and Lithium Ion Batteries question

Old 12-16-2016, 06:21 PM
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paco ritter
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Default Futaba and Lithium Ion Batteries question

OK guys, here's what I want to do. Using a Futaba R6014HS receiver which I'm told is capable of handling the 7.2V power of a Fromeco Lithium Ion battery. Using Savox SV-1270TG High Voltage servos on all control surfaces which will also handle the high voltage of the Lithium Ion batteries. Now, I hate to use this expensive and high powered servo on the throttle. Can I use a standard servo (6V) with a regulator in line bringing the voltage to this one servo to the 6V range? Is this possible? Anyone ever tried this method?
Thanks
PACO
Old 12-16-2016, 08:29 PM
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No, I would not go that route, since HV servos are not at all that expensive. The Hitec HS430BH is HV and is only about 14 bucks. Hitec also has an HV sport digital that runs a little more, check them out.
Old 12-17-2016, 04:26 AM
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paco ritter
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PilotPete, I think you are on to something there. I never research how inexpensive some of the HV servos were since I was dealing with only more expensive Savox 1270's. I really didn't want to put one of those on the throttle. I purchased a less expensive $23 Savox HV servo for the throttle. Thanks for the advice.
Old 12-17-2016, 07:59 AM
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And just to reinforce the point, I am flying 3 planes right now with 2S Fromeco Relions with the 6014HS receiver. Zero issues. With any of the Futaba receivers it is your servo voltage that is the true limit on voltage you use. All Futaba 2.4 receivers can handle unregulated 2S lipos/2S Lions with no issues at all.

Bill M.
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Orange County, CA
Old 12-17-2016, 08:34 AM
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Bill, that is exactly what I intend to do with my set up. I have one (7) ch, three (8) ch and one (14) ch receivers laying around awaiting a plane to be installed into. My winter project will be a scratch built (with the help of a short kit from LazorWorks, Wichita Falls, TX) BIG HOTS from the days of the Dan Santich HOTS kits. My all around favorite plane from way back when. I want another, so I am gathering parts and pieces to make it happen. After some reseach around Litium Ion batteries and Futaba receivers, I arrived at the same conclusion you have stated. The servos are the limiting factor. So, I went with Savox high voltage servos but didnt want to use one of the more expensive ones merely for a throttle servo. Was searching for a way to get a standard servo to work in this application. Did not realize I could get an HV servo as cheap as they were offered as my focus had been on the more powerful ones, not the less torque versions. That is the route I chose to take, less expensive HV servo on the throttle and my BIG HOTS should be well equiped with radio and servo gear. Spring should bring my BIG HOTS to life and ready hopefully for a lifetime of good flying!!!!
Old 12-17-2016, 04:10 PM
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Silent Is this Futaba's position? Dan.

"All Futaba 2.4 receivers can handle unregulated 2S lipos/2S Lions with no issues at all."
Old 12-17-2016, 04:51 PM
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Originally Posted by All Day Dan View Post
Silent Is this Futaba's position? Dan.

"All Futaba 2.4 receivers can handle unregulated 2S lipos/2S Lions with no issues at all."
Here is what Bax from Futaba has written:

http://www.rcuniverse.com/forum/futa...08hs-7-4v.html

http://www.rcuniverse.com/forum/futa...iver-7-4v.html

http://www.rcuniverse.com/forum/futa...ell-lipos.html

http://www.rcuniverse.com/forum/futa...al-servos.html

http://www.rcuniverse.com/forum/futa...r-voltage.html

There's more, but you get the idea. You will not hurt the Futaba FASST/FASSTest receivers using unregulated 2S lipo or lion packs. Add to that that I have tested most of them with 3S lipos myself and 5 amp loads (all I could do at the time) without any issues.

I am currently running 3x6014, 2x6303, 2x7008 and 2x7003 receivers all on 2S lipo or Lion with zero issues and have done so for years.

Bill M.
Team Futaba
Orange County, CA
Old 12-17-2016, 06:45 PM
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Bill, Perfect. Thanks, Dan.
Old 12-17-2016, 07:15 PM
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That pretty well sums it up, any Futaba 2.4 receiver will handle the Fromeco 7.4V bats without a regulator as long as your servos will withstand said voltage. I got that covered, too!!!
Old 12-18-2016, 04:56 PM
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Bill, after that great response, let me try another. As the voltage is raised to the receiver and especially the servos it can be expected that the current drawn by them will increase. Can it be assumed that it is directly proportional to the increase in voltage or will actual flight testing be required? Dan.
Old 12-18-2016, 06:44 PM
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Voltage = current X resistance. Or Current = voltage / resistance. The resistance is the same, and current and voltage are proportional in this case. You can bench test this, and not discover a failure in flight. Or spend $20 for insurance. http://www3.towerhobbies.com/cgi-bin...RKkaAtaf8P8HAQ
Old 12-20-2016, 10:51 AM
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Originally Posted by All Day Dan View Post
Bill, after that great response, let me try another. As the voltage is raised to the receiver and especially the servos it can be expected that the current drawn by them will increase. Can it be assumed that it is directly proportional to the increase in voltage or will actual flight testing be required? Dan.
Hi Dan,

This is an old discussion that has been addressed, tested and documented several times in the various forums. We're not talking simple ohms law here because we're doing work with a dynamic device called a servo. A servo does not act like a simple resistor! The power consumption of a servo varies with the load applied to it. As we increase voltage, for a given amount of work being done (airload on surfaces in this case) the current will actually go down as our simple and common watts formula (P=IE) comes into play. If "P" is constant and "V" increases, "I" has to go down. Now if more work is being done, certainly the current will go up. Servo idle current will increase very slightly but only an extremely low amount so this is really no factor.

I know when switching from 4 cell to 5 cell batteries in the Nixx days, when using the same cells, my power consumption went down when the only change in an airframe was the battery. As always, I'd suggest flight testing to satisfy personal curiosity. Just be sure to only change the one variable, the battery voltage. Fly several flights at the lower voltage then several similar flights at the higher voltage. Charge after each series of flights to see what the battery consumption was.

Last edited by Truckracer; 12-20-2016 at 10:58 AM.
Old 12-20-2016, 12:39 PM
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Thanks Truck. As usual you're right on. Dan.

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