Help! EDF speed and throttle issue

Flying_Fast74

New member
I have made foam board RC F-18 super hornet following Ben Harber's plans. I am using parts listed below. The issue I have is - After connecting the battery, when I increase the throttle on transmitter, the edfs speed up and reach to only about 80% max speed before max throttle position and then slow down to 30-40% of max speed when I shift to max throttle position. If I were to immidietly push the throttle to max speed instead of gradually, the EDFs will go to max speed, but stay at that speed only for a few seconds and then slow down to about 30-40% of max speed. In each subsequent tests with the battery still connected, the EDFs reach their highest speed about 10-20% slower than the time before. E.g. if I reconnect the battery and EDFs go to 80% max speed before slowing down to around 40%, then the next tests it will reach only upto 45% max speed, and then slow down to 30% of max speed, so on and so forth. Once the speed dips to or below that 30-40% mark, the speed remains constant irrespective of the throttle position. My battery is fully charged (though, I would welcome suggestion of a battery level tester). I want to make sure the edf speed gradually increases and reaches the highest at the full throttle position in repeated tests. I have used one ESC for each EDF. Both of my ESCs are connected to one battery, and are calibrated as well.

Connected parts list:
1) TWO Powerfun EDF 50mm 11 Blades Ducted Fan with RC Brushless Motor 4300KV (Balance Tested for EDF 4S RC Jet Airplane).
2) TWO ZTW Beatles Series 50A 60A Brushless ESC with BEC for RC Airplane 4S 6S (Beatles 60A ESC with Connector)
3) 3.5mm Banana Gold Bullet Connector Extension Cable for RC Brushless Motor ESC Extension Cable Wire (16AWG 30CM).
4) Flysky FS-i6 radio transmitter and FS-iA10B 4.0-6.5V/DC 2.4GHz 10 channel receiver.
5) OVONIC AIR 3000 50c mAh battery. 11.1V (Main Battery for ESCs)
6) ONE Blomiky 8.14Wh 7.4V 1100mAh 35C Li-ion-Po Battery with JST Plug (For External BEC)
7) BW RC Servo BEC UBEC 3A 5V Airplane Receiver Servo Power Supply
8) Onkuey T Plug Male to 2 T Plug Female Parallel Battery Connector Cable (120mm)
 

leaded50

Legendary member
agree with @LitterBug , cant see anything ells should be the problem. Check if some connections on bananas, battery, or ESC eg are very hot though.
 

Flying_Fast74

New member
Sounds like your battery can't handle the load of two EDFs and is sagging. What happens if you do the same test with a single EDF connected?

Thanks for the tip. I'll try connecting the battery to only one of ESCs. Would the solution to this be getting a bigger battery that can handle two EDFs, or something else?
 

Matthewdupreez

Legendary member
Thanks for the tip. I'll try connecting the battery to only one of ESCs. Would the solution to this be getting a bigger battery that can handle two EDFs, or something else?

THIS IS THEORETICAL

just looking at it and your battery your are using is rated for a constant current of 150 amps..
the esc's on the other hand are only rated for 60 amps....

if you are using 2 esc's then your max current would be 120 amps, and your battery is rated for 150amps...

it would seem as if it is not your battery that is the problem, but rather your esc's...

please correct me if i'm wrong...
@leaded50 @LitterBug
 
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LitterBug

Troll Spammer
just looking at it and your battery your are using is rated for a constant current of 150 amps..
the esc's on the other hand are only rated for 60 amps....

if you are using 2 esc's then your max current would be 120 amps, and your battery is rated for 150amps...

it would seem as if it is not your battery that is the problem, but rather your esc's...

please correct me if i'm wrong...
@leaded50 @LitterBug
Not so fast. Battery C ratings are not always what they seem. The THEORETICAL max is 150 A. I can show you a pile of batteries, that for various reasons either never met, or no longer can do their rated load.

Testing individual motors will also help determine if one is pulling more load than it should.
 

Flying_Fast74

New member
When I try only one EDF connected to my main battery, it spins fine all the way up to 100% as well as if I have an external BEC for the RX and servos. The manufacturer for the EDFs say that the max continuous current is 38A and it has a 4300KV/4S motor (probably explains why it could be sagging; I overlooked that & just realized), so they recommend a 40A ESC & a 3s battery. I have 60A ESCs, so I'll try using a 4s battery and see what happens.
 

quorneng

Master member
An ESC will only deliver the amps that the motor requires. My research suggests that motor on a 3s will draw 20.1A so well within the capability of your 40A ESC.
The fact that with only one motor connected it runs correctly means you have either a bad battery or some very poor wiring or both!

Get yourself a Watt meter (as recommended on your similar post on another site!). It will tell you how many amps you are actually drawing and the voltage the battery falls to whilst it is doing it.