Transmitter / receiver issues, help needed pls

[PatMc]

Daire, the problem is probably because the ESC has a linear mode BEC.
Linear BEC's reduce the input voltage down to the output voltage level by absorbing and dissipating the difference in the form of heat. This means that the higher the I/P voltage the fewer servos they can run without overheating & also reducing the O/P voltage.
For example if you were to use a 2s lipo the BEC would probably run 4 servos with no problem but of course your model would then be underpowered.
Not all ESCs with linear BECs are restricted to the same balance of I/P voltage against servo count but they are all restricted by the heat they can absorb or dissipate. Also some servos take more current than others so the actual servo count can differ but is always restricted with any linear BEC.

Some ESC's have switching mode BEC's. SBEC's reduce the voltage in, as you might guess, a switching process that I'm not going to explain further other than to say it's much more efficient, produces less heat & is much less restricted in servo current against I/P voltage.

AFAIK most ESC's below about 40A rating only have linear BEC's. However I received an email the other day from Hobbyking advertising the launch of a new range of their Turnigy Plush brand ESC's that all claim to have SBEC's fitted. As yet I've not bought one from this new range so can't recommend them on experience but I have used Turnigy Plush ESC's from their previous range with no issues.

Here's a couple of links to the Turnigy 20A ESC & to the 30A ESC . If you do decide to get one of these my advice would be the 30A if the model can accommodate the greater bulk.

PS other than being a customer I have no connection with HK.

Edited By PatMc on 22/06/2019 22:10:04

[DAIRE CONNOLLY]

Hi Folks,

Thanks for the replies on this thread - its been a steep learning curve so far.

What I have now is a 3.7v battery powering the Rx and servos separately and the ESC only powering the motor which works (obviously). 3.7v seems to be grand to power the Rx and servos without an issue and I've been able to get the machine off the ground so far.

I'm going to leave it in this configuration, find a larger place to fly this yoke, and get it in the air properly.

Thanks again

(edit: not 2s - just 1 - 3.7v)

Edited By DAIRE CONNOLLY on 24/06/2019 17:02:43

[David Tayler]

Daire, Do you know the brown out voltage for your receiver? 3.7 volts seems rather low for a receiver supply .However you say 2s. if that is a lipo that gives 7.4 volts which is high for many servos. I hope your new esc will give 5 volts which is fine for most receivers and servos.

[DAIRE CONNOLLY]

From the online docs it does seem to be 4v minimum but the 3.7 seems to work ok.

[Frank Skilbeck]

Posted by DAIRE CONNOLLY on 24/06/2019 17:04:27:

From the online docs it does seem to be 4v minimum but the 3.7 seems to work ok.

Until you've pulled a few mah out of the battery then the volts will drop, lipos start off at 4.2v fully charged (with no load), dropping to 3.6v (no load) when almost fully discharged. So you may be OK initially........................

Note you can get voltage boosters which raise the Lipo voltage to 5v, often used in small discus launched gliders, I've used then with a small single cell (700 mah) lipo.