in the last example the motor current setting on the 12S was reduced from 60a motor current to 50a motor current limit, a reduction factor of (1/1.2 = 0.8333)… in addition to increasing the gear ratio by a factor of 1.2… this is why they both have the same wheel thrust and top speed, and why the 12S system in the previous example had lower motor heating (purple line, top middle chart - ohmic heating watts 2 motors bldc).
but suppose instead you increase the gear ratio by a factor of 1.2 with the 12S system, but leave the motor current at 60a limit for both… now you have increased efficiency with 12S (green line, top left chart) & increased thrust with 12S (yellow line, bottom left chart - vehicle thrust in pounds), but the motor heating is the same for both (purple line, top middle chart - ohmic heating watts 2 motors bldc), top speed nearly the same for both (yellow line, bottom left chart - vehicle thrust pounds 2 motors bldc) & battery amps lower with 12S (purple line bottom right chart - battery amps 2 motors bldc).
I must admit that I’m genuinely surprised by the idea of people pushing the limits so far for little to almost no gain in real life scenario.
The thought of having a much higher chance of malfunction in my board while driving at 25+ mph and being thrown head first into tarmac or in front of the car, scares me to death. Therefore I use 10s wich I still think its a bit of a stretch.
Again guys electric boards don’t have redundancy one failure means total failure, and that could easy be the line between life and death for someone.
Stop giving dangerous advices to people, just because your are doing something and it went OK so far.
My i suggest that one of the guys with a good reputation makes a poll where people can vote about the rate of failure and the voltage they where using. If many enough people answer that could give us a somewhat clearer picture.
Maby
@Hummie, @professor_shartsis@chaka@onloop could be the right person.
Best regards from an engineer who has learnt d through his study that you should always aim to have at least 20 to30% headroom. Specially considering the outcome in case of a failure.
not that its a safe outcome but when i’ve had escs fail they havent launched me and instead just lost throttle. that could be very dangerous if leaning forward and expecting it, or if you were going downhill and you lose your brakes, but so far i cant blame a broken esc but can blame faulty receivers for many injuries.
~10 km/h speed increase going from 10s to 12s. That’s difference between holding up traffic and being able to move with traffic around where I live. Gear ratio sometimes can’t be tweaked. Now I have both torque and speed/E-MTB.
Dual drive, dual receiver. Redundancy right there.
I suggest you try a 10S battery connected to 2 independent drivetrains - each one having an ESC, a receiver, a motor, and a drive wheel. So the ESC are not connected together except for the main battery + and - wires
That way if you have a failure, it’s very likely that you will still have one wheel with power and brakes still
Right. No CANBUS and no split PPM. Not all RC controllers can do this. I know the mini remote can and I know another one can, but I forgot which other one.
The only connection between the drivetrains are the main power wires and radio waves
If all it needs is another receiver for the remote then sounds like its well worth the additional fail safe. Gonna check if it can be done with the firefly!
Oh sorry I meant @b264 as he’s gone full on esk8 and sold his car if I recall right. Definitely would be nice to have though if you get caught out in sudden rain
I can hardly belive that. How fast are you going with 10s and 12s. Assuming that you go 50kmh in 10s that would translate in theoretical 60kmh with 12s. Air resistance, spin resistance and more other factors play inn and they grow almost exponentialy with speed increases. So I do suggest you try and measure the real speed differences first. And don’t go by the calculator.
So here comes my 3 questions :
1)How often and for how long do you ride at 60kmh by the way.
2)most of the time people have to chose between 10s5p or 12s4p. Have you thought for the slight voltage såg that you will get with a lower available current draw?
3) Are you aware that motors also have an efficient voltage range so even if you raise the voltage could mean that the efficiency drops a bit.
So adding :
Air resistance,
Roll resistance,
Motor efficiency
Lower number of parallel cells
And some other factors that I’m not remembering right know, your real speed increase is far smaller than your theoretical. Except maby downhill and in vacume.
BTW, will running 12s but limiting erpm in VESC firmware to 10/123.7Kv be effectively as reliable as 10s? Will the VESC basically cap itself at 80 percent duty cycle and replicate 10s? That might be a reasonable way to combat voltage sag on low parallel count setups
