Direct wire Reciever to 7.4 volt battery?

[Craps]

I know alot of you use the UBEC to hook up the reciever that powers the steering servo, but about hooking it up directly to 7.4 volt li-po or 7.2 volt nickel battery packs without a UBEC?

Is it too much voltage for the reciever and steering servo?

Will the reciever have more range and less chance to glitch on higher voltage?

Will the steering servo have more torque and be faster on higher voltage?

Just curious if anybody had tried that and what were the results?

[Mr. Constructor]

i tried that some time ago with these receivers:
jeti 4channel micro FM, Graupner/JR synthi SB 6, Proton FM Synthi, simprop 7channel synthi, Futaba FM F 123 R; several older AM receivers.
the result: the Graupner/JR SB 6 takes it best, as it has a built in BEC for use with these lipos, i use 2 of them in my big scalers as there should be extra safety with a receiver liion pack.
The jeti just died after a longer period, same with AM ones (but some of these receivers came back after letting them cool down.)
The proton could easily hold the power, but the power (7,4V) is also trannsferred directly to the servo, the newer digital ones do NOT like that ;-)
some older analog series do hold that, with having more power, more speed and likely they wear out faster too.

in general it could be said, that the sevos cannot handle it very good, the receivers might do that, but most (only exception: Graupner/JR SB 6 Synthi) will not be usable as the volatge for the esc AND the servos will be too high for continous use.

Several older fet servos are used to a separate harness cable wich should be connected to the 6 cell main battery (10th cars only) these will do fit very well in this thing with a Proton receiver.

so best solution: JR SB 6 synthi with BEC for up to 2 servos (wich should be OK, unless these 2 are way too powerful (meaning 2x 11 kg digital ones with aluminium cooling sink) and then a Liion or lipo pack for powering it.

[TheSteve]

Many receivers can handle the voltage, most servos though will suffer a lot. Using 6 volts generally shortens the life of a servo, whats 7.4 to 8.4 volts going to do to them?(nothing good...)

[Craps]

If the reciever can take it, then one of the giant Hitec servos for robots that is rated for 7.4 volts is faster and has more torque if the reciever can take it for larger scale vehicles in the 1/5th to 1/4th range.

I was going to double up on servos and R/Xs using the Futaba HRS RXs!

[studysession]

I have my stupid hat on - what is UBEC?

[Craps]

UBEC stands for Ultimate Battery Eliminator Circuit

It is the same as a BEC too!

Some ESC don't have the power wire to run the rx or the steering servo, so we add a BEC to reduce the 7.4 or 7.2 volt pack down to 5 or 6 volts to run the rx and servo.

[Chase023]

Why not go with the Hi-tec HRS5995TG?? It is a regular sized servo with super torque that has more than alot of the Giant scale ones? (it is a robotic servo as well but I am going to use two for my custom MT project).

Specs
7.4 volts at 416.61 oz/in @ 0.12 secs
6.0 volts at 333.29 oz/in @ 0.15 secs

http://www.juggernaut23.com/Juggernaut%202%20(Jugg%20Dreadnaut)/Hitec%20HSR-5995TG%20000.JPG
http://www.juggernaut23.com/Juggernaut%202%20(Jugg%20Dreadnaut)/Hitec%20HSR-5995TG%20002.JPG

[studysession]

OK Ultimate BEC. I have seen those before. Was thrown with the abbreviation. I have always used RX packs. Never used the Ultimate BEC.

[tcolesen]

UBEC's are external circuit boards that take in as much voltage as 35volts (or more possibly) from the battery pack(s) and turn it into 6volts. Some UBEC's supply up to 3 amps (maybe more?). I am very, very soon going to be making my own UBEC (except maybe more of a BEC without the Ultimate) using electronic components and a circuit board. It should be able to handle 1 amp and 16volts. Later on though, I could very easily change it to work with 35volts. The cost for this was ~$5, the heat shrink tubing (for wrapping it in) being $3 of that price. If anyone wants directions for this, shoot me a PM.

Sorry for being a little off topic.

EDIT:
I started typing this, and then when I posted it there were already 2 more posts!

[Craps]

Why not go with the Hi-tec HRS5995TG?? It is a regular sized servo with super torque that has more than alot of the Giant scale ones? (it is a robotic servo as well but I am going to use two for my custom MT project).

Specs
7.4 volts at 416.61 oz/in @ 0.12 secs
6.0 volts at 333.29 oz/in @ 0.15 secs

http://www.juggernaut23.com/Juggernaut%202%20(Jugg%20Dreadnaut)/Hitec%20HSR-5995TG%20000.JPG
http://www.juggernaut23.com/Juggernaut%202%20(Jugg%20Dreadnaut)/Hitec%20HSR-5995TG%20002.JPG


That is what I meant when I posted this:
If the reciever can take it, then one of the giant Hitec servos for robots that is rated for 7.4 volts is faster and has more torque if the reciever can take it for larger scale vehicles in the 1/5th to 1/4th range.

Now if my Futaba HRS reciever will take 7.4 volts. I guess a phone call to Futaba would let me know.

[OptimaMan]

You could simply make a plug with some diodes in line with the power. Each diode in series will drop the voltage by .4 volts. Get three of those in series with the power wire (keep in mind a diode has polarity and will allow current in only one direction) and you can do a direct line from the batteries w/o receiver pack or UBEC. Larger diodes usually have pretty high amperage ratings.

[Craps]

So the power wire in the servo wire harness can be seperated to a battery wire direct and still have a controller wire/s from the rx. The power wire to the rx would then have the 3 diodes to drop the voltage to 6 volts.

I think I am clear on this. RR sent me a link with wiring schematic to do this also.

I am going to call Futaba today.

Thank you

[Mr. Constructor]

Be careful, the diodes may be getting seriously hot, they could melt the shrinkwrap, as most asre only for around 1 Amp rated (seen in various tech manuals) so the heat will be a problem AND the low battery, if ther battery comes to an end, the car will be undriveable due to the less voltage, the receiver and servos fail and the car will run out of control, the circuit in these UBEC boards does prevent this as the voltage it controlled and the receiver will be totally shut of when the voltage will go down, the safety should be the first thing to think of, no matter if it costs 30 USD, you car costs a lot more so the money should be worth it !!!
(esp. in high powered 5th scalers this AND a failsafe will be the best thing to protect your car and wallet !!)