I start looking into this in more detail, but it raises more questions than answers. Just for clarification; the difference in this discussion is what your system can deliver without permanent damage (i.e. temperature or current getting to high so you get irreversible damage) and what is required to move a car from A to B in a certain time frame. For the same condition (weight, time) it will take the same energy regardless of what system you have (2S or 3S) to move the car from A to B. This energy is equivalent to what the “car” load your system with in wattage. So for the same load you require the same wattage (power) from your system. So derived from P = U x I (power = voltage x current). This is a simplification, but more about that later. Consequently, when voltage increases the current decreases and vice versa for constant power demand.
The Ohms law is only true for ohmic system like resistor and wires which is not the case for a brushless motor. If you look up a motor equation you will see that you have to take into account reactive forces like EMF, etc. But if you could apply Ohms law your statement would be true. However, I have stated from the beginning that you cannot increase voltage above your rating without risking permanent damage. If your system is rated for 3S you can run 3S and lower, A 3S system does not run hotter than a 2S if you e.g. use a Traxxas VXL system. Yeah, it will if you do not change your gearing, but that it’s like running any wrong pinion in your 2S car.
Obviously, by lowering your voltage you will have less available power, and for the old system using NiCd or NiMh batteries with a typical cell voltage of 1.2V that would discharge to around 1.0V would give you a total loss of 1.2V for a six cell pack. That is equal voltage drop for a lipo battery (8.4V -7.2V), so why do we not see this “power loss” from start to end for a brushless system, like we did for the “old” system? It got me thinking. An ESC is a PMW device (Pulse Width Modulation) and it’s basically using its duty cycle to control the average voltage the motor sees. The longer the cycle, the higher the average voltage which again increase the RPM of your motor. What if the ESC modulates so you never get above 7.2V regardless you battery voltage (8,4V -7,2V). Thus the car will be 100% consistent during your race. Also, that make sense that Novak rate their motors with 7.2V and not 8.4V. But this is just my theory.
- Electric 1/8 off roaders, where much of this discussion typically occurs, generally don’t use the same motor for different voltage setups. With 4S a 1900kv or so motor is common, but those running 6S tend to run 1400kv or so motors (of course there are exceptions for both). If voltage did not impact power why change motors (load)?
I never stated that voltage did not impact power (well it was not my intention anyway
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