Quote:
Originally Posted by hemiblas
...Idea: Lets say you have only 6S battery config but you only need 14.8V because 22.2V out. It would be nice to program the controller with a max voltage out setting to run the motor within spec. Or maybe a percentage of battery output feature that would limit the voltage of the battery to the motor.
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There are only two ways to limit the voltage to the motor:
1) Through chopping off the excess voltage. This is known as linear regulation and is extremely inefficient because the excess voltage X current flow = power needed to be dissipated on the FET. So, if you drop the voltage from 6s to say 4s, that's a 7.4v drop. At even a low 20A, that's 148w! So that's out.
2) Through PWM. This involves sending narrower pulses to the motor. So, if you send 6s pulses (22.2v) at 10% duty cycle ("DC"), the motor is seeing an average voltage of 2.22v. 50% DC = 11.1v, and so on. This is what gives you efficient variable speed capability. The trouble with limiting the DC, as others have noted, is that everything runs better at full voltage. So, despite the somewhat less efficiency of limited DC, this would be the only practical option.
So, to get what you want, it would just be a matter of setting your throttle EPA to something less than 100%. Or, you could use programming on the ESC instead, but it's just easier to use the radio (and allows you to change on the fly).