I am looking in to making a UAV quadcopter and I don't know how to calculate what ESC to use with the motors I have picked. I am looking at buying the HobbyKing Red Brick 10A ESC and the Turnigy Aerodrive SK3 – 2118-3100kv Brushless Outrunner Motor. Will these work together? Is it overkill? What battery would I want to use that will be light but have a long battery life? Is it the most efficient it can be for the price and application? If anyone has personal experience or knowledge in this all input and ideas are welcome.
Will this ESC work with these motors
brushless-dc-motorlipomotor controllerpower supplyuav
Related Solutions
Short answer:
Yes, you can use up to 15 LiFePo4 cells in series (aka 15S) at the input of the ESC without any problems.
Long answer:
LiFePo4 cells definitely work all Lipo ESCs... as long as you don't exceed the max input voltage of the ESC.
Your specific ESC lists that it can handle 12S Lipo batteries. This means, it can take an input voltage is greater than >50V (>4.2V*12). This is also the reason it states that you can use up to 36 NIHM cells, which are 1.5V peak voltage (1.5v*36 = 54v). 54V is the max input voltage for this ESC.
This means, you can use 15 LiFePo4 cells in series without exceeding the input voltage rating. The peak cell voltage for LiFePo4 cells is bit over 3.5V/cell... so 3.5v* 15 = 52.5v (which is below the max rated volatge)
More details:
The internals of an ESC are switching power regulators, which output a frequency modulated AC to the motor (except sometimes cheap BECs, are linear regulator, which get super hot). The switchers compensate for any battery sag, allowing you to pretty much put in any non-alkaline cells at the input (because alkaline batteries have way too much ESR). The only way to damage the ESC is to exceed the max input voltage. Some ESC may list the actual voltage, while most just list the max number of LiPo cells that the ESC can take.
Yes, it should be safe. However there are a few things to watch out for:-
Unlike a battery, power supplies are poor current sinks. During commutation and PWM the motor generates current spikes which can feed back into the supply and cause the voltage to rise. This effect can be reduced by adding a high capacitance low-esr bypass capacitor across the controller's power input terminals. This will also help to suppress voltage spikes caused by inductance in the power wires.
If the current would exceed 10A at full throttle (100% PWM) then rather than simply lowering the throttle you should either reduce the load or use a lower Kv motor. The reason for this is that motor current is multiplied by the inverse of PWM ratio. For example at 50% PWM an average power supply current of 10A corresponds to 20A at the motor, with even higher peak currents. This current is drawn from the supply 50% of the time (during PWM 'on' time) so peak power supply current could also be 20A or more.
When the motor is accelerating it will draw more current, which might cause the PSU to shut down if it exceeds 10A. To avoid this you should ramp the throttle up slowly so the dynamic torque load is less.
Switch-mode power supplies often have a sensitive current monitor which will shut down the PSU on even brief overloads. This won't cause any harm but is annoying.
Best Answer
They should work, and as the info on the motor page states, you should use a 2 cell Lithium-Polymer battery.
A good calculator can be found here, it will let you know how much you can lift, run for, etc and should help you find the best propellers and best capacity and required discharge rating to use.