okay, so as I understand it, when you have regenerative braking allowed for a certain amount, the VESC will bring up the voltage to match the BEMF minus the allowed regen current, which goes into the battery.
doesn’t this mean while regenerative braking sends power back into the battery, it generates less power than it takes to apply braking right? makes me wonder why the ESC sends power to the battery when it could just use that power to brake.
You can’t use that power to brake
All braking is regenerative, the energy needs to go somewhere, you can’t delete kinetic energy,
couldn’t the ESC take the voltage created by the BEMF and just send it right back along a single phase wire to stop the motor? the voltage would then match the BEMF voltage, so it would brake right?
That’s not how a three phase motor works.
the way I understand a 3-phase motor is each phase is a separate copper winding, and the phases need a wave (square or sine) sent down at least 2 of them in an offset sync to produce rotation, a voltage is measured on the 3rd phase to keep the other 2 in sync. I assumed that powering a single phase to maximum with the other 2 at minimum would pull the magnets in the stator to a single position, therefore applying a brake.
No, because now you’re not actually fighting BEMF, which rotates with the motor.
BEMF wins this tug of war and blows your ESC up with it.
oof, would specialized hardware be able to do this then?
No. You can’t magically delete energy with more energy. It needs to go somewhere.
ahh I see the flaw in my thinking. clear as day.
You’re confusing voltage with current here. The BEMF voltage opposing the ESC voltage doesn’t generate any excess heat, because it’s not actually flowing anywhere.
The only undesirable effect from the BEMF is that it sets a hard limit to the maximum speed a given motor can spin at a given voltage, because beyond that point the BEMF would be stronger than the drive voltage, and would prevent any power from flowing into the motor.
Again, you’re mistaking EMF( electromotive force, aka voltage) for power. The ESC can control the amount of current it draws from the motor during braking, thereby controlling the power as a function of current x voltage.
(Maybe this has already clicked for you; that’s fine, I like to talk but you don’t have to listen 
)
As @MysticalDork explained nicely, you seem to be confused about what constitutes “power”. Voltage is not power. Voltage is like pressure. Voltage doesn’t flow, it only causes current to want to flow, which can only happen if you close the circuit.
It’s like a balloon. When I blow up a balloon, the air inside is pressurised slightly. There’s now a “voltage” from the inside to the outside. If I make a hole in the balloon (closing the circuit) the air (current) will flow.
I have no idea if that actually helps. The important thing to remember is that voltage is simply a desire for current to flow. You can create as much voltage as you like without letting current flow, so long as the resistance is high enough. (I mean, technically a very super tiny amount of current is always flowing even when you have the circuit disconnected, but it’s really so ridiculously tiny that it’s irrelevant.)
Picture a battery. There’s voltage between the two terminals all the time, but only when current flows is power being drawn. A motor can generate a voltage without generating heat or otherwise dissipating any power because there’s no current flowing so there’s no power to dissipate.
ahh yeah, voltage is potential and current is a force
Apologies if this has been asked before. What would be the max battery amps with a 13s8p made from LG M50LT 21700 cells?
Cheers.
So 14.4A is the rated max of the cell (always monitor for overheating).
Your 8 p groups multiply this 14.4A to make a theoretical max battery amperage of 115A.
This is assuming your battery is built safely and can deliver that via the nickel strip and other connections.
Good to know I have headroom. It was built by marsen energy in western Australia late last year. I’ve been running it conservatively but now I’m aiming to see what it can really do.
So in Vesc tool you can set both battery current max and a motor current max?
That’s correct.
Also the motor current max can be much much higher than the battery current max.
Motor current limit determines low speed torque and acceleration. Battery current limit determines higher speed torque and acceleration.
