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Frsky OPerating Voltage Range

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David Jacobs21/04/2017 09:36:16
45 forum posts

I'm moving from Spektrum to Taranis so just getting my head around various matters. I note that the X8R reciever that comes with the Radio has an operating Voltage of 4-10v - Does this mean it will only work with up to a two cell?


Andy4821/04/2017 10:03:34
1257 forum posts
65 photos

I presume you mean 2 cell lipo. If so yes.

Why would you want to use a higher voltage? Few if any servos will survive 10v never mind higher.

Spektrum receivers have a maximum voltage of 9.6v.

David Jacobs21/04/2017 10:21:25
45 forum posts
Yes i do mean 2 cell Lipo. Maybe I'm misunderstanding the effect. I use 4 cell lipo.
Denis Watkins21/04/2017 10:38:21
2386 forum posts
122 photos

David, your 4 cell lipo will still drive 16.8v through your ESC to the motor

It is just that servos and most receivers work between 4.8v and 6v

Look up set ups to suit your needs

IanR21/04/2017 12:44:54
746 forum posts
4 photos

David, the ESC you are currently using with your 4 cell drops the voltage to (whatever - I've forgotten) to operate the servos and receiver. The same will happen with your Taranis.


Andy4821/04/2017 12:58:26
1257 forum posts
65 photos

I presume your speed controller will have a BEC. Otherwise your Spektrum receiver would have fried long ago. The BEC reduces the voltage down to 5-6 volts to drive the receiver and the servos. The power is sent down the servo lead from the speed controller.

If converting to Taranis, you want to be really careful to reset the throws on your model as the Taranis drives the servos further than a Spektrum, which might either give control problems or cause the servos to stall or jam.

David Mellor21/04/2017 13:27:51
331 forum posts
80 photos






Posted by David Jacobs on 21/04/2017 09:36:16:

I'm moving from Spektrum to Taranis so just getting my head around various matters. I note that the X8R reciever that comes with the Radio has an operating Voltage of 4-10v - Does this mean it will only work with up to a two cell?



Hi David.

I moved from Spectrum to Taranis. The short answer is that nothing has changed. What worked for you with Spectrum Tx and Rx will work for you with Taranis Tx and Rx.


However....... something in the way you have worded your question is worrying me slightly because it indicates you might not understand something that could turn out to be important.


One of the most common types of arrangement encountered is the one in which the Rx and servos are powered directly from the ESC via a small circuit (part of the ESC itself) that supplies the Rx and servos with current at a constant voltage. The small circuit within the ESC that provides this power to the Rx is called the BEC (Battery Elimination Circuit). The BEC provides that power at a constant voltage suitable for any make of receiver and servo.  This is what Andy has just said in his post (I only saw his answer after I'd posted my reply).


I'm assuming that all your models have ESCs that have built-in BECs - simply because that is pretty much the norm for most mainstream park flyers and "out of the box" ready-built models under, say, £200.


BUT.....there are other ways of powering an Rx and the servos. Not all ESCs have BECs, and a plane may not necessarily have an ESC in the first place (e.g. a glider). I may be jumping to the wrong conclusion, but it appears (from the way you worded of your question) that you may not know or understand that situation. Which means you might accidentally burn your Rx and/or servos out if you move onto a different system than a simple ESC with integral BEC.


If you still don't quite "get" what Andy has said, or what I have said then you need to ask again - loads of people here will help and we've all had to go through the learning process ourselves too!



Edited By David Mellor on 21/04/2017 13:32:29

Andy4821/04/2017 14:04:56
1257 forum posts
65 photos

If he's using a 4S lipo then he must have a BEC in the circuit somewhere, otherwise the Spektrum receiver would have sent smoke signals and refused to play long ago.

David Jacobs21/04/2017 15:24:16
45 forum posts

Hi and thanks for all in depth responses. Yes I use straightforward Park Fly type planes, typically using a Plush ESC (with integral BEC). In my stupidity I watched a YT review of FrSky V8R7-II 2.4G 8CH Receiver where the tuber said that that due to the voltage they could not be used in a 3 cell... Otherwise I would never have question it. Thanks again...

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