Here is a bench test I have done to find out if a 2s to 4s Afro ESC's can run on 6s.
ESC’s and Label Specs
Afro Slim ESC 20amp 2- 4s battery afro_nfet.hex firmware
Afro Bec ESC 30amp 2- 4s battery afro_nfet.hex firmware
Afro HV ESC 20amp 2- 8s battery afro_nfet.hex firmware (control)
ESC component specs taken from the manufactures data sheets.
Afro Slim 20amp 2-4s:
5v MCU supply regulator LM78L05 Max input 30v Max load 100ma
NFets FDMS8018 Max Voltage 30v, Continuous Drain @ Ta=25°C = 30amps
BC817-40W 6CW max Voltage 45v 500ma
All components are rated up to 150°C
Afro bec 30amp 2-4s:
5v MCU supply regulator LM78L05 Max input 30v Max load 100ma
NFets FDMS8018 Max Voltage 30v, Continuous Drain @ Ta=25°C = 30amps
BC817-40W 6CW max Voltage 45v 500ma
All components are rated up to 150°C
Afro HV 20amp 2-8s:
5v MCU supply regulator LM78L05 Max input 30v Max load 100ma
(But this LM78L05 is fed from two DAR transistors that take the HV voltage and step it down to 12v, their Max voltage is 40v) this is why I think the Afro HV was de-rated from 12s to 8s.
NFets FDMS86540 Max Voltage 60v, Continuous Drain @ Ta=25°C = 20amps
(If the 5v MCU supply was by-passed and you fed the MCU with 5v from another source the Nfets are rated at 60v) So I would assume the ESC will run at 12s with a new 5v supply for the MCU.
All components are rated up to 150°C
Test equipment:
Power supply 60amp 24v power station
Amp and Watt meter Turnigy 130A
Tarot 4114 motor with 15 x 5.5 prop fitted
Test meter with temperature probe
Motor stand with weight scale attached for thrust readings
Servo tester for PMW control
Method
Apply a constant 24v supply to a power meter then to an ESC to measure amps drawn with the esc connected to a standard motor and propeller running at 50 % PWM throttle controlled by a servo tester and run for 10mins whist monitoring temperature, amps, watts and thrust.
Result
ESC Amps Draw Watts Temp Thrust
1st Afro slim 20A 5.65 133 47.1C 1114g
2nd Afro BEC 30A 5.68 134 53.8C 1160g
3rd Afro HV 20A 5.3 125 46.0C 1111g
Conclusion
It Appears as if the Afro Slim 20amp and the Afro Bec 30amp ESC’s are capable of handling the use of a 6s battery as a power source, according the specs of the components provided by the chip manufacturer, the temperature of the components was very similar and the amps drawn the same. So if you wanted to hide the ESC’s in the arms of the Multi-rotor (provided cooling holes for air was allowed for) then this will be fine and they will run on 6s power.
Caveats
Slim ESC wiring was upgraded to suit a higher amp draw and the use of 6s batteries, (although the original wiring fitting is 20amp rated so should be fine for most Multi-rotors) the other component’s on the boards were not investigated, so no information on them is known.
Use this info at your own risk.
Video https://youtu.be/91rc37c5YBQ
Photos
Comments
I agree with Peter, you have to had quite big safety margin to make sure you never exceed maximum voltage rating on FET. This voltage consist of battery voltage and induced voltage on motor wiring during transitions of speed(braking). Here is application brochure from infeon for MOS-FET in baterry aplication, and for 24V at battery is 60V MOS-FET voltage recommended. If you will use 4S ESC on 6S battery, ESC probably burn out sooner or later.
You have interpreted the component capability based upon their maximum values. For instance, a 78l05 on 24v input will not be able to carry a current of 0.1A as it will have to dissipate about 1.9W. You need to calculate the junction temperature based on the heatsink capability to see if it remains within spec. I would suggest it will cook itself to death!
You have also not considered the practical aspects of the FET's working in a switching environment with inductance and capacitance that can result in voltage spikes above the supply voltage. It is not unusual to allow for a 2 to 1 margin when using a power component. I would suggest 6S which is 25v gives no margin on a 30v rated FET.
I would not recommend running the Afros at anything greater than their rated values. I would also not recommend putting ESC's in tubes as they are designed to have cooling air passing over them to limit the junction temperature rise.
regards Peter
I'll have to give the DYS models a go. QC is terrible on most ESCs so it's something I deliberately look for now. Try pulling the heatshrink off the bullet connectors on a random ESC. In many cases the soldering is very poor.
Um do you mean me James?
I have the afros on two quads and haven't had any issues so far. I have however gone over to the DYS Esc's now from BoltRC (Hobbyking sells them too, but Bolt is faster) and have had no issues with them either, but they are much smaller and lighter than the afros and seem to have better QC. They also have higher manufacture cell ratings.
I've had one 30A afro catch fire while on the ground (running off a 3s, throttle in neutral) and two others produce stuttering at high throttle settings. The stuttering turned out to be due to poor solder joints on the power lines, but it hasn't given me much confidence in them. I know others like them, though, so I'm keen to hear your thoughts.
Nice!
Have you tested them to full throttle as well?
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