Brushless Motor not drawing rated amperage?

sceadwe · Jan 02, 2013, 09:08 PM

So I am part of my college's ROV team and in charge of the propulsion team. We are testing a brushless motor system for our ROV.

Today we finally got some propellers (Traxxas 4mm shaft RC Boat Props) however in our initial tests today in water the motors are drawing only about 2.5A-3A at max throttle in water which is far short of the rated 14A continuous draw in air? Maybe I am missing something but we are using E-Flite Park 450 rated with 80A-HV Seaking ESCs.

I'm not sure why they seem to be under powered but my intuition says that it's the smallish size of our props.

I am interested in hearing what any of you on here have to suggest on getting better performance out of our brushless system.

Thanks

nick_75au · Jan 03, 2013, 08:21 PM

Basically the load determines the amp draw, not the nameplate ratings, all my boat brushless setups draw less than the nameplate ratings and I set them up deliberately that way so additional cooling (usually provided by airflow from the air prop) is not required, enclosed hull provides no airflow.

Two ways to improve the thrust, either change the props to larger ones or increase the voltage, check out my blog for an article on sizing motors and props,

cheers
Nick

Jan 02, 2013, 09:08 PM	#1
sceadwe Registered User Joined Dec 2012 1 Posts	Brushless Motor not drawing rated amperage? So I am part of my college's ROV team and in charge of the propulsion team. We are testing a brushless motor system for our ROV. Today we finally got some propellers (Traxxas 4mm shaft RC Boat Props) however in our initial tests today in water the motors are drawing only about 2.5A-3A at max throttle in water which is far short of the rated 14A continuous draw in air? Maybe I am missing something but we are using E-Flite Park 450 rated with 80A-HV Seaking ESCs. I'm not sure why they seem to be under powered but my intuition says that it's the smallish size of our props. I am interested in hearing what any of you on here have to suggest on getting better performance out of our brushless system. Thanks

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Jan 03, 2013, 08:21 PM	#2
nick_75au Tygum Lagoon Terror Australia, QLD, Regents Park Joined Mar 2007 3,108 Posts	Basically the load determines the amp draw, not the nameplate ratings, all my boat brushless setups draw less than the nameplate ratings and I set them up deliberately that way so additional cooling (usually provided by airflow from the air prop) is not required, enclosed hull provides no airflow. Two ways to improve the thrust, either change the props to larger ones or increase the voltage, check out my blog for an article on sizing motors and props, cheers Nick