Servo voltage question

[Greg Johnson]

Here's my scenario. My throttle and mixture servos are rated at 4.8v to 6v. I want to use a steering servo with a range of 6v and up. I'd like to switch over to a LiFe battery which is 6.6v. Will that voltage damage my throttle and mixture servos?

 

[Hydro Junkie]

Depends on the servos. Some could work for a while but the lifespan would probably be reduced. What servos are you using?

 

[Greg Johnson]

Depends on the servos. Some could work for a while but the lifespan would probably be reduced. What servos are you using?

Savox SW 0250MG and SW 1210SG

 

[Mark Anderson]

I have never used Savox, But my experience with other brands I would make the switch to 2 cell life with no worries. A fully charged nicad or nimh 5 cell is right around 7 volts. If you are concerned there are several small inline regulators that can be put in the system between the reciever and servo. I have run nothing but life since the first A123 cells came out in power tools. I have never seen a problem.

 

[ricwally]

I am not sure about your particular servos. But, Savox usually gives servo ratings at different volts in the specs. Most ratings listed are 7 or 7.4 volts. If you look down in the specs. It will give servo ratings at a lower voltage. I would bet that you are safe at 7 to 7.4 volts with no issues. Almost everything built these days have a fudge factor built into them for situations just like this.

 

[Grimracer]

ANYTHING over 6 and you are spinning the chamber.

Sure they might last awhile.. but.. then.. they might not.

I have a picture some place around here that shows the results of 6.6 on a 6V servo.... its UgLy!

Grim

 

[Hydro Junkie]

I am not sure about your particular servos. But, Savox usually gives servo ratings at different volts in the specs. Most ratings listed are 7 or 7.4 volts. If you look down in the specs. It will give servo ratings at a lower voltage. I would bet that you are safe at 7 to 7.4 volts with no issues. Almost everything built these days have a fudge factor built into them for situations just like this.

I have a simple question for you. You say it's safe to run a 4.8-6V servo on 7-7.4V. I'm assuming you have a smart phone with a USB style charging cord. Since USB ports run 5V, would you be willing to charge your phone from a 7-7.4V source? It should be safe, considering there is a built in fudge factor just for situations like this in all electronics, right?

 

[Greg Johnson]

ANYTHING over 6 and you are spinning the chamber.

Sure they might last awhile.. but.. then.. they might not.

I have a picture some place around here that shows the results of 6.6 on a 6V servo.... its UgLy!

Grim

So I see you are a big fan of the Li Fe batteries. This in fact is why I wanted to make the switch as opposed to NiCad. NiMh is failing on me. In fact I just had a set melt all of my electrics in my 7.5 tunnel as one of the cells shorted internally. It scorched the wood radio box but did not start a fire. This is why I'm now down this path.
With the 7.5 OB I'd like some higher torque for steering but need just standard waterproof servos for throttle and mixture.
I started a different thread where I was going to try to run a mixture of HV and LV servos but everyone recommended against it.
When I look at the specs any servo giving me the torque I want needs at least 6V to be an option. I hope this sheds some light on what I'm trying to do. It seems the simple fix is 5 1.2v nicads. Then I'm not over the 6V rating of the throttle and mixture servos and at the minimum for the steering servo.

 

[Grimracer]

Greg, Hope you are well,

Your right I am a HUGE fan of LiFE... BUT.. if I have low voltage servos in anything they get a regulator. I use the Futaba PS-10BR Reg. . not cheap!.. but they work great.. here is the link.. just for your information..

Futaba PS-10BR

NiCADS are my next choice.. i have ZERO love for NiMH...

I dont follow the "water proof" servo path. Part of it is Futaba does not make one.. (thats to bad) and the other is... me... they would go in a box anyway.. !

Be well

Grim

 

[Greg Johnson]

Greg, Hope you are well,

Your right I am a HUGE fan of LiFE... BUT.. if I have low voltage servos in anything they get a regulator. I use the Futaba PS-10BR Reg. . not cheap!.. but they work great.. here is the link.. just for your information..

Futaba PS-10BR

NiCADS are my next choice.. i have ZERO love for NiMH...

I dont follow the "water proof" servo path. Part of it is Futaba does not make one.. (thats to bad) and the other is... me... they would go in a box anyway.. !

Be well

Grim

Thanks for the additional information.

 

[timothy johnson]

Greg, without a long explanation I have been using the 6 volt Life batteries with the Savox servo's you listed and also several Hitec waterproof servo's with zero issues over several years. Please understand I'm not an expert, what I have done in the past with a question like your's is contact the manufacture which I did about your same question and was told everything should be good. With that said people like Grim are experts and are careful to give you a simple yes or no because they know all the complicated electrical parts of the servo's, batteries and RX's. Grim I believe is a Futaba rep and he has helped me in the past and really know's his stuff. Your in the right place to get great advice from great people who will always help you and I . Hope this helps.

 

[John Beardslee]

Greg, all chemistry batteries are at their peak voltage right off the charger. I’ve used LiFe chemistry in my helis from the time they first came out. I only regulate the tail rotor servo voltage. All others run full voltage but a habit I was taught is to run the system a little before flying and it knocks the peak voltage down into a much better range. I do the same with all my boats but only by running the rudder servo. I have a Futaba BR-2000 tester that allows me to put a load on battery packs and watch voltage changes. Very useful for peace of mind.
Thanks John

 

[ricwally]

Hydro Junkie, I have no clue who TF you are. But, running a servo and powering some sort of application are two different scenarios! And, actually the 1210 servo he was inquiring about is rated for 7 volts. So, if you are dumb enough to think that there is always a constant voltage to anything using power? You better think again. Try checking the power to your home at different times during the day. You are probably someone that doesn’t drive over the speed limit either!
Give me a break!

 

[Hydro Junkie]

Actually, I'm a Navy trained avionic tech that works in civilian aviation. With that said, when someone says to "go ahead, it will handle it", that's asking for trouble. Same deal with running a car on regular or E-85 gas that says only use premium unleaded in the owners manual or running 5-30 in an engine that says 10-40 because some hack says it's fine. Either one of those scenarios will result in a damaged engine and major amounts of cash to repair it. If the servo says use a specific voltage, use it. You are correct, there is a fudge factor, based on how much the batteries will hold at peak charge. A 6 volt nicad pack will probably top out at 6.5 or so, about where a LiFe pack is rated. You put a fully charged LiFe pack on a meter, it's probably over 7 volts. That will fry a 6 volt servo in short order. And, just for the record, I don't know of anyone under the age of 75 that drives the speed limit. If you try to drive 60mph on the freeway in my area, some one will end up dead

 

[Greg Johnson]

Actually, I'm a Navy trained avionic tech that works in civilian aviation. With that said, when someone says to "go ahead, it will handle it", that's asking for trouble. Same deal with running a car on regular or E-85 gas that says only use premium unleaded in the owners manual or running 5-30 in an engine that says 10-40 because some hack says it's fine. Either one of those scenarios will result in a damaged engine and major amounts of cash to repair it. If the servo says use a specific voltage, use it. You are correct, there is a fudge factor, based on how much the batteries will hold at peak charge. A 6 volt nicad pack will probably top out at 6.5 or so, about where a LiFe pack is rated. You put a fully charged LiFe pack on a meter, it's probably over 7 volts. That will fry a 6 volt servo in short order. And, just for the record, I don't know of anyone under the age of 75 that drives the speed limit. If you try to drive 60mph on the freeway in my area, some one will end up dead

Don't want this to go any further south than the original thread request for information. Hydro Junky you hit the nail on the head as the reason I posted the question. My history has been with nicad and NiMh and after a full charge they sometimes get into the 7's on voltage. I assumed it would be similar for LiFe except they're already rated at 6.6 so was that added voltage enough when fully charged to fry the 6v rated servos. The message I'm getting from most is don't try it. I'm good with that answer and will take necessary steps to avoid that.

 

[Bill Brandt]

I have sold many, many 250s and 1210s as well as many others in the Savox line. No customer has raised the issue of premature failure. I myself run 7.4 lipos with all Savox. No issues but the choice is yours.