Futaba Receiver and High Voltage Servo Setup Question

[zxb466]

Hello Everyone,

I have a Futaba R404SBS receiver and the voltage specification on it says 3.7v-7.4v. I'm going to be using "high voltage" 7.4v servos with a 7.4v battery but am not sure what I need to make this work. Is there some type of voltage regulator on the market that drops the voltage down below 7.4v for the receiver?

And if so, how do I make my receiver output 7.4-8.4v for the "high voltage" servos when it receives voltage below 7.4v? Do I need a special high voltage receiver or something else? I've never run high voltage servos so am not sure how to do this or how people run these high voltage setups. This is for my 1/8th scale Team Associated RC8B4.1 nitro buggy. Would appreciate anyones advice and input on how to accomplish this. I've seen people running the high voltage servos but not sure how to do this when the futaba receiver is rated at 3.4v-7.4v.

Thank you!

 

[ferrebee88]

Hello Everyone,

I have a Futaba R404SBS receiver and the voltage specification on it says 3.7v-7.4v. I'm going to be using "high voltage" 7.4v servos with a 7.4v battery but am not sure what I need to make this work. Is there some type of voltage regulator on the market that drops the voltage down below 7.4v for the receiver?

And if so, how do I make my receiver output 7.4-8.4v for the "high voltage" servos when it receives voltage below 7.4v? Do I need a special high voltage receiver or something else? I've never run high voltage servos so am not sure how to do this or how people run these high voltage setups. This is for my 1/8th scale Team Associated RC8B4.1 nitro buggy. Would appreciate anyones advice and input on how to accomplish this. I've seen people running the high voltage servos but not sure how to do this when the futaba receiver is rated at 3.4v-7.4v.

Thank you!

From my experience, a standard 2s lipo pack will work just fine with a receiver rated for 7.4v. I've done this without issue with spectrum and futaba.

 

[DavidB1126]

A fully charged 2s pack is 8.4v so it would blow the receiver. You would probably need a external BEC

 

[zxb466]

From my experience, a standard 2s lipo pack will work just fine with a receiver rated for 7.4v. I've done this without issue with spectrum and futaba.

I think I'll just get a BEC just to be safe. Futaba customer service said to never input any voltage higher than 7.4v. What receiver do you run?

 

[ferrebee88]

I think I'll just get a BEC just to be safe. Futaba customer service said to never input any voltage higher than 7.4v. What receiver do you run?

I use a Futaba R203GF in my 1/5 with a 2s battery.

 

[WickedFog]

I think I'll just get a BEC just to be safe. Futaba customer service said to never input any voltage higher than 7.4v. What receiver do you run?

I have never seen a receiver that wouldn't handle 8.4v. That doesn't mean there are some that won't. I've just never had one that wouldn't. But Futaba would know best. They're likely just covering their butt, as most electronics won't actually burn up at their upper limit. There is always a little buffer there. Me personally, I'd try it. But Futaba Rx's aren't cheap, so yeah, a BEC is a pretty good safeguard if you're not the adventurous type

 

[tntpoof]

This is one of those RC wrong info from Brand . The 7.4 is off it means a 2 cell lipo ... There are a few others that have been said by Brands....
A fully charged 2 cell lipo will not blow the receiver ..if your that worried then you .pull the pos(+0 and negative wires out futaba plug and add the lipo to those 2 wires then plug single signal wire into receiver.

 

[Greywolf74]

A fully charged 2s pack is 8.4v so it would blow the receiver. You would probably need a external BEC

I think I'll just get a BEC just to be safe. Futaba customer service said to never input any voltage higher than 7.4v. What receiver do you run?

A BEC is technically the correct way to go, but as some of the other folks have said, I've never had a 2S lipo damage a receiver. Typically, if something is rated for let's say 7.4V in this case, the engineers will have built a tolerance of a couple/few volts in to it for safety reasons. Good quality electronics will often times have overvoltage protection built in to them also. (not to be confused to overcurrent protection) If you exceed the recommended voltages, you always take a chance, but 1V difference in this case shouldn't matter, and of course the longer you run the pack, the lower the voltage will drop anyway. It will likely drop from 8.4V to 7.4V within a handful of minutes.

 

[WickedFog]

This is one of those RC wrong info from Brand . The 7.4 is off it means a 2 cell lipo ... There are a few others that have been said by Brands....
A fully charged 2 cell lipo will not blow the receiver ..if your that worried then you .pull the pos(+0 and negative wires out futaba plug and add the lipo to those 2 wires then plug single signal wire into receiver.

Add the lipo to what two wires? You lost me here man. He has to connect the battery to the Rx to power his servos. There is no signal wire there.

 

[Greywolf74]

Add the lipo to what two wires? You lost me here man. He has to connect the battery to the Rx to power his servos. There is no signal wire there.

LOL, I was wondering the same thing

 

[RustyUs]

They do make LiFe receiver packs if overly concerned about things.

 

[WickedFog]

They do make LiFe receiver packs.

Yes.
Spektrum 1450mAh 2S 6.6V Li-Fe Receiver Battery SPMB1450LFRX https://a.co/d/iCf9BIB

 

[Weezel]

Add the lipo to what two wires? You lost me here man. He has to connect the battery to the Rx to power his servos. There is no signal wire there.

LOL, I was wondering the same thing

@tntpoof is talking about wiring the servo directly to LiPo battery.
LiPo battery positive and negative to servo (they wouldn't be connected to receiver). And servo yellow wire(signal is the only thing to receiver).
Basically a BEC bypass. TNT just described what the harness from Holmes Hobbies does.

 

[tntpoof]

Figures..l ok the servo has 3 wires. A positive wire a negative wire and a signal wire. so you connect the positive wire to the positive side of the battery and the negative to the negative.

and how is a life battery going to give a high voltage servo the power and voltage this guy is after it can't

 

[RustyUs]

Figures..l ok the servo has 3 wires. A positive wire a negative wire and a signal wire. so you connect the positive wire to the positive side of the battery and the negative to the negative.

and how is a life battery going to give a high voltage servo the power and voltage this guy is after it can't

Yeah, the actual voltage in high voltage (HV) servos can mean a couple/many things depending on manufacturer's specs of their servos. Lots of servo options out there that will give a person the torque & speed they want at less than 7.4 volts. I personally would use a 2S LiPo in OP's situation... not enough variance for me to get concerned about.

 

[tntpoof]

most times theres major differences in speed and torque id be concerned .

 

[zxb466]

Thanks for all the input on this! I think I'm going to take a risk and plug in a fully charged 2s lipo to my Futaba receiver that says max 7.4v. Hopefully it doesn't fry it lol. I will update this post once I get my hands on a 2s lipo and test it out in this week.

 

[DavidB1126]

Really wouldn't do it. I'd rather get a bec and run it that way.
Did that on one of my old radiolink receivers rated for 7.4v. plugged in a fully charged 2s pack. The circuit board got really hot and the led light blew out. Can't remember if it still actually worked or not.

 

[Weezel]

Really wouldn't do it. I'd rather get a bec and run it that way.
Did that on one of my old radiolink receivers rated for 7.4v. plugged in a fully charged 2s pack. The circuit board got really hot and the led light blew out. Can't remember if it still actually worked or not.

It's too bad the manual for the Op's receiver isn't on the Futaba website. I know on my 304sb receiver descriptions said what it was rated for but in the manual it also gave a bigger (wider) acceptable voltage range.

 

[zxb466]

Will a 10 amp BEC work for two servos? I have two AGFRC 74KG high voltage servos but can't find the wattage or amperage rating for them