Technical, Techniques, Hints, and Tips > BRUSHLESS Motors and Speed Controllers

esc with motor help

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mmartin1980:
power question.... will a 70a esc be ok with a 1200kv brushless motor, using 4S lipo battery, ive tried the maths and think ive gone a little backwards somewhere

JimG:
How long is your piece of string? Seriously you need to know the wattage of the motor to find out. Watts = volts times amps so if you know the wattage of the motordivide it by the voltage of your pack ( say 16V at full charge ) and this will give the maximum current it should take. The kV rating tells you nothing about the current only how fast it will rev off load. Best to use a Wattmeter to check the actual current under load when the propeller is in the water to make sure you are not overloading it with too big a prop.
Jim

chas:
If you tell us exactly what motor it is, probably someone on here will be using one and you'll get an answer.

malcolmfrary:
It depends on the motor and the load.  A lightly loaded motor (small and/or shallow pitched prop) will draw much less current than one with too much prop.  With brushless you can only go off what numbers the advertising claims since the motor is only half of the deal.  The ESC is the part that directs the current to the motor coils.  Nothing happens without it.  And something to tell it what to do.
With a brushed motor, life is simple - you connect the battery and measure the current. 
In the brushless world, you need an ESC with enough reserve on paper and something to control it with.  Then you can hope that everything works when it is hooked up, and there is the chance to find out what it does actually take, but even when the average current is known, there is a huge amount of de-rating to do to take care of start-up loads and other transients.

mmartin1980:
seem it need to be installed in the boat, which is nowhere near ready for water, but im confused as how i measure the load on th emotor when i need the esc to use it and dont want to damge the motor or esc i have is they are wrong and cant take the load


what i have is as follows:
Motor - Surpass Rocket 3760 1200kv
Battery - 4S lipo (14.8v)
ESC - i have 2 i could use if appropriate:
1: surpass rocket watercooled 70A
2: aircooled (attached fan and heatsink) 120A

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