So, when a receiver says “4.8-6 volts”.....does that imply that the “.6” extra voltage is okay? Said another way, there isn’t a 6-volt pack, so is that a hard number and must be regulated? Or is using one of the common 6-volt battery combinations okay?

Specifically, I’ve got a Futaba R617FS receiver and a 6.6 volt LiFE pack I’d like to use.

Question also applies to servos but I was more concerned about the receiver.

If the answer is regulation, I have to wonder why these manufacturers wouldn’t factor in common battery voltages in their product design.

Thank you.

JAM

For our purposes receivers are not voltage limited...that is you can run straight 2s lipos (8.4v) with no problem. So you’re fine with life packs.

^^^^What he said^^^

I can confirm for you that all current Futaba 2.4 receivers will works fine on 2S lipo voltage. It is the servo voltage of the servos you are using that limit system voltage.

FWIW, I tested the R617FS on 3S lipo voltage pulling 10 amps and it worked perfectly.

Servos are another matter. There are some brands that when they say 6.0 volts max, that is an absolute limit. Other brands are more tolerant. I ran several Futaba 3150 servos, rated at 4.8 volts on 2S LiFe (7.2 volts fully charged) for a couple of years with no issues. So it really matters what brand you are using.

Awesome, guys. Thank you.

Regarding the servos - they’re Futaba 3004 servos. Not a high-end servo by any means. But I ran them a bit with the pack plugged in and it seemed to work okay. I guess the question would be how long they will run that way. I can’t imagine an extra “.6” volts being a deal-killer. Again, why anyone would design a servo to take 6 volts, but not the voltage of the common 6-volt packs is beyond me.

The servos are in a large scale Decathalon so basic sport flying. Nothing extreme. Was just hoping to make good use of the pack I had.

I'm running R617FS in 7 planes on 6.6V LiFe
With both analog or digital servos
Mixed bag of servos from several manufacturers
None are listed as HV
1 plane has 3004s
started 4 yrs ago
No problems

Originally Posted by Motomazzo

Awesome, guys. Thank you.

Regarding the servos - they’re Futaba 3004 servos. Not a high-end servo by any means. But I ran them a bit with the pack plugged in and it seemed to work okay. I guess the question would be how long they will run that way. I can’t imagine an extra “.6” volts being a deal-killer. Again, why anyone would design a servo to take 6 volts, but not the voltage of the common 6-volt packs is beyond me.

The servos are in a large scale Decathalon so basic sport flying. Nothing extreme. Was just hoping to make good use of the pack I had.

Those servos will be just fine on a 2S LiFe pack.

As to why some servos are less tolerant, that's an unknown. I can tell you that all the Futaba servos I am aware of do not have that kind of sensitivity. Especially the standard size / larger digital servos.

More great info. Thanks guys.

FWIW - I was just talking to the guy I received the plane from and ironically, he used a 6.6v LiFe on the plane as well. So, I think we’ve put this one to bed. Y’all have a good Memorial Day weekend!

JAM

3004 servos date from several years ago... at the time almos all rc'ers used nicd packs a 4 cell nicad is rated 4.8 to 6.0 volts, fully charged gets a bot over 6.0 volts, a 5 cell nicd gets closer to 7 volts fully charged, no problem on said 3004 servos.
Life's work fine

Originally Posted by Judge

FWIW, I tested the R617FS on 3S lipo voltage pulling 10 amps and it worked perfectly

I would like to believe you but the manual doesn't recommend it

Originally Posted by haribo

I would like to believe you but the manual doesn't recommend it

Well, you are certainly free to believe what you wish to. The manual is fairly dated and long experience of myself and countless others have proven that this receiver, and every other current Futaba RX is fully capable of operating on unregulated 2S lipos. It is your servos that limit the battery voltage you choose.

All of these receivers have internal voltage regulators that regulate the input voltage to a lower voltage for receiver operation while the bus that provides power to the servos continues to operate at the supply / battery voltage. As others have stated, no issues operating these receivers at higher voltages. I've never heard of a receiver failure due to running at typical HV voltages. Going to the next level of 12V plus may exceed the input voltage limits of some of these receivers but we're not discussing that here.