every motor has the same potential of torque or power but not every motor has the same potential of top speed
yes, it has difference top speed.
slower motor has more resistance and needs less amps to achieve the same torque.
Anyways, 5t better for slow trails. 4t better for roads. 5t less amps hungry but less top speed.
yes, field weakening is not in sim.
slower motor does not heat up faster or slower. People say that that it heats faster because people supply it with too many amps or are not able to cool it down fast enough.
Motor max power much depends on how fast it can shed accumulated heat. When you pump lots of amps into motor its temp raises faster compared when you pump only few amps therefore prolonged high power usage increases motors temp and motors performance capabilities depends how fast you can eliminate that heat. When you go fast you pump lots of amps, you generate more heat, you need bigger better battery to sustain high speed, also you need more amps.
use a cheaper/weaker/smaller/ battery and controller and it will do it's job and have good performance
It's heavy powerful motor. You current battery is too weak even for 5t, but you still can ride with it but with better battery ebike would run better. Your battery is 50a constant and 150a peaks. With 3kw motor I would recommend at least two such battery packs, 12p20s instead yours 6p20s.
compare following battery packs:
6p * 8a = 48a
12p 96 = 96a
18p *8a = 144a
Mpre p more amps you can draw from pack. With higher discharge cells you need less p but usually get less capacity.
what do you think will be realistic top speed with my 72v, 21mah, continous 50 amps, peak 150 A battery, a unlocked sabvoton 72150 and a 5T motor in a 18 inch rim ?
~70kmh and ~90kmh with fw but you will finish your current battery if will use fw.
speed depends on battery voltage. These speeds are with fullu charged battery, when it discharges you will get less and less speed. When it's discharged you might have ~55kmh without fw.
Speaking about FW.
If you will turn ON fw to gain speed than you will have more amps demand and even higher voltage sag.
So as i already mentioned i'd really love a lot of acceleration but would also like to be able to get up to 80 kph. As i think now with a 4T Motor and more amps both is possible right
no, too weak battery. 4t will have high sag in top speeds. Also sag in acceleration. But it is still usable.
Insane acceleration and a good top speed ?
Insane is very strong word. I would say it will be rideable and better battery is required especially with faster wind motors.
how do i calculate the amps of a battery pack ?
usually who builds pack writes it on it. Otherwise you can determine yourself. Its discharge capabilities depends gow well it is built and mainly depends how many cells in parallel, in you case 6cells in P and it says 50a constant (parallel cells number multiplied by constant one cell discharge capabilities, 6 * 8 = 48A, about 50A.) Battery building is whole another story.
One more example from true case scenario with your to be setup:
Assume you get 4t and the controller and run with your battery and set it for best performance by settings amps to 150/350. You accelerate and see big voltage drop, your battery heats, battery life shortens drastically, because of voltage drop your top speed less than it would be with better battery.
You can't ask many amps from battery which is not built to do so. Actually you can, but it will decrease in performance, generate excessive heat (not desired effect), voltage drop (less speed), brake prematurely.