There is no good reason to lower the motor amps to 20a motor amps each on the 18s setup. You can draw 40a battery amps total (20a battery per motor) while at the same time putting 30a motor current through each of the 2 motors.
So please explain any rationale for reducing the motor current limit from 30a per motor to 20a per motor on the 18S setup. You’re giving up torque by doing it, but for no rational reason.
What I am saying is that you have 50% extra amps on the battery side with a 12s battery.
lets says 36 samsung 30q cells
12s3p = 60 amps battery max
18s2p = 40 amps battery max
Lets assume 100% efficiency. You can only draw 20a per motor at max speed on the 18s setup. On the 12s setup, you can draw 30a per motor at max speed.
My point is, you will always have 50% extra amps available through your system on a 12s setup at any given speed/throttle position.
There is also no reason to not use the 50% extra amps you have available on the 12 setup.
Yes, I understand your rationale for lowering the battery amp limit on the 18 S set up, but there is no logical reason to lower the motor current limit.
Bro, you can set the motor amps to a million amps. The point is, you don’t have the amps on the battery side. Where are these motor amps coming from?
Because the vesc is a buck converter, it lowers the voltage to the motor while increasing the amps. You will always be putting more amps through the motor than are drawn from the battery unless you reach 100% duty, which is impossible on a vesc, because it only goes up to 95%.
But the max motor amps available on a 12s will always be 50% higher than on a 18s setup.
In the example above, at any point, you will always be able to get 50% more motor amps on a 12s setup. I don’t understand what you are trying to say.
Show me a single data log where the motor current per motor is lower or the same as the battery current per motor. You won’t find it because it can’t be done.
Say what? No one is claiming this. What does that have to do with anything?
I’m saying you have a good reason to lower the battery current limit with the 18S set up because, as you say, you have less P groups. But there is no good reason to lower the motor current limit, because the motor current per motor is always higher than the battery current per motor.
But it is still constrained by the wattage of your battery.
Do you agree that a 12s3p and a 18s2p of the same cells have the exact same output watts?
No, at low speeds (2mph), with either the 12 S set up or the 18 S set up, both pulling 30 a motor amps per motor, neither is getting anything close to the battery current limit out of the battery. Neither setup is drawing 30a battery per motor or even 20a battery per motor.
Let me rephrase
Do you agree that a 12s3p and a 18s2p of the same cells have the exact same maximum potential output watts?
Sure, but that doesnt mean you have a good reason to lower the motor current limit with 18S.
For example 18S, constant 30a motor current per motor while accelerating, you’ll get something like 2a battery amps at 0mph, increasing with speed, then maybe around 20mph you’ll hit the 20a battery current limit per motor, at which point the battery current will remain constant with further acceleration and the motor current will be decreasing. Close to top speed you’ll have around 20a battery current and 21 motor current with 20a bat limit and 30a motor limit per motor.
Now go a step further. whats the reason to not use the extra available 50% amps for a 12s setup?
Pick any number for your 18s setup motor amps. You will always be able to pick +50% for the same 12s setup. Why wouldn’t you?
Now, please. I beg you. Do the same experiment for a 12s setup where your motor amp max is 45 amps.
50% more battery amps with the 12s setup is the same wattage from the battery, so you are using it, but only from maybe 20mph to 30mph, below that you probably can’t get anywhere close to the battery limit at full throttle but you are hitting the motor limit.
In the first phase of acceleration you are hitting the motor current limit but not the battery current limit.
In the second phase, you are hitting the battery current limit but not the motor current limit.
In the 3rd phase, you have hit the duty cycle limit, but you aren’t hitting either the motor or battery current limits.
But the motor current limit is higher on the 12s setup. So no difference here either.
But you have no rational reason to lower it on the 18S setup.
At those low speeds, the motor voltage is low so it doesn’t matter if it is coming for a 12s or 18s battery.
At low speeds you can draw 30A motor per motor on either the 18S or 12S setups, and you won’t be drawing anything close to the battery current limits on either setup (either 20a battery or 30a battery per motor).