Brushed/Brushless motors, speed controls, gear drives Discuss all aspects of brushless motors, brushed motors, speed controls (ESC's), gear drives and propellers in this forum.

dumb question

Old 01-08-2009, 03:15 PM
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Default dumb question

hello all.
i have dumb question.
can you run a inrunner with max amp of 30 with a battery that puts out 44 amps continious the esc is a 70 amp. i guess what i need to know is will the esc put out tha continous amps of 44 or will it only put out the amps it needs to operate the 30 amp the motor. thank you .
Old 01-08-2009, 03:31 PM
Walt Thyng
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Default RE: dumb question

the only dumb question is the one you don't ask.

Now, as to your question. First, batteries only put out amps at the request of the motor. A battery is a storage device with potential power that must be put to use by a device of some sort. The battery is capable of putting out 44 amps continuous IF the motor asks for it. Some "headroom is always nice in an ESC; if your motor can handle 30 amps its nice to have at leasat a 35 amp esc. a 70 amper is somewhat overkill, but will work just fine at 30. The esc will attempt to put out all the amps the motor calls for until either it or the motor burns up, or the battery dies. An esc works a lot like the throttle on the old radial engines, it turns the flow of voltage on and off in order to control the speed of the motor.

There's a whole bunch more theory here, but the above should answer your basic question.

One piece of advice: most of us still follow the 80% (some 75) rule for LiPo use. Never discharge beyond 80% of capacity; never draw more than 80% of the "C" rating; never charge at more than 80% of the capacity. this rule extends battery life, shortens flights and avoids fires!
Old 01-08-2009, 04:29 PM
Dr Kiwi
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Default RE: dumb question

Just to add - what you must do is select the correct prop so that your 30A max motor is not going to try to draw more than 30A or (comparable to Walt's 80% rule which I reckon applies to motors as well) better, not much more than 24A. If you put too big a prop on your motor, it will try to draw more, because the battery CAN supply it, and the ESC CAN let it through.

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