Safe voltage level for receivers?

[durok]

As was briefly touched on before on another thread, many of our most commonly-used receivers have relatively low "listed" max voltage levels.

For example, the R203GF that comes with the Futaba 3PV I have is rated for 4.8 - 7.4V (shared with servo).

My issue is that I have a Mamba X ESC and a ProModeler 470 servo, and I'd like to use the maximum 8.0v output from the Mamba's built-in BEC to get close to what the maximum amount of power the servo will deliver - it's rated for 8.4v.

However, the power from the BEC would then be 0.6v higher than the Futaba receiver is rated for....

I REALLY don't want to have to wire in a separate BEC, or add an extra LiPo just for the servo.

When I search on the internet, I've run into many comments in RC forums (mostly aviation) that state that usually receivers are OK with some extra voltage, it's servos that are more worrisome.

Anyone have any feedback or information on this?

I worry, because Futaba receivers are not cheap!

[mikemcE]

Rx bypass

Use a bec........
Hang up and Drive

[svt923]

If a receiver is rated for 7.4V, I always take that to mean it is safe to be powered by a 2S lipo (8.4V max voltage) as would be the case in a nitro vehicle. This has been my experience for all of the mainstream brand receivers I own (Futaba, Sanwa, Spektrum) but it may not be so for some of the cheaper brands. The only receiver I had die from too much voltage was a Orange Spektrum compatible one from Hobbyking that suffered near instantaneous death at 8V.

[Jim85IROC]

Rather than use an expensive external BEC for a servo, you can make a cable similar to that Holmes cable above with a cheap BEC tied to the receiver instead of the servo. This will drop the ESC voltage to 5-6v for the receiver. This way you can use a cheap 5v UBEC, or better yet, a $1 buck converter, as shown in the diagram below

[Rekreant]

Its a risk for sure, but I run my tactic that is rated at 6.6v at 7.4v with no noticeable issues. At best I think you may shorten to life of the receiver, but as for how much shorter there is no way to know. A lot of these ratings are simply to stay within certain standards and requirements. FCC, CE, and the other lower quality Chinese standard(cant remember the name) have various requirements to put their seal of approval on your product.

[mewalsh100]

Like mikemcE, I run an RX Bypass harness on all my Rigs along with an external Castle BEC. My Rigs have HH BLE or BR-XL ESC's, and in most instances could deliver what I would need for my Hi-Torque servos. For me, it's more about an ounce of prevention really.

[durok]

I really appreciate all the input and there are certainly more options offered up here than I had thought of!

I have an unused new CC BEC 2.0 Waterproof, and I have a Holmes Bypass cable, but I also have an extra FlySky receiver that is rated for 8.4v...

...and as much as I wanted to try out my Futaba 3PV, I can simply setup a second profile on my FlySky GT3C tx for the Bomber and use the max 8.0v output from the Mamba X BEC safely.

I'll save my Futaba radio for the second Bomber build, which will be using a Holmes SHV500 v1 servo, allowing me to set the BEC from the Mamba Monster X that is going in that build to a lower voltage, as the servo will be getting power from a GearHeadRC XT60 inline-connector that has a servo lead wired to it, allowing the servo to be powered directly from the 3S packs.

I can't use one of those inline connectors on this first Bomber, as it will be using a 4S pack powering the HH 540 Revolver 1800kv - 4S is too much power for the SHV500 v1.

I really would prefer to not have to solder in a BEC, and this way I can avoid it on both rigs.

If later I feel that 8.0v is less than optimal for the ProModeler servo, I will give in and wire in my CC BEC 2.0 Waterproof using my HH Bypass cable, allowing me to program an output of exactly 8.4v, from the available range of 4.75 to 12V.

Thanks again, everyone!

[Jim85IROC]

I run my Promodeler on 8v in my Bomber and I'm very happy with its performance.

[durok]

Originally Posted by Jim85IROC

I run my Promodeler on 8v in my Bomber and I'm very happy with its performance.

That's great to hear, many thanks my man!