Model Boat Mayhem

Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: Captain Flack on July 07, 2015, 06:26:38 pm

Title: ESC size
Post by: Captain Flack on July 07, 2015, 06:26:38 pm

I have acquired a 37" MTB in Fibreglass :-) which has come fitted with twin Brushed 540 motors turning a couple of smallish brass props.  It has only one 30 Amp MTroniks ESC which keeps cutting out.  I assume it's because it gets hot.  If I leave it, it cools down and it's fine again.   Obviously a pain in the neck. {:-{   The batteries are twin 9.6v giving a combined voltage of 9.6V and some 7, 200 mAmp.
Does anyone know what size ESCI should be using as I want to keep both motors on the left hand stick.
Thanks.
Neil

Title: Re: ESC size
Post by: Tug-Kenny RIP on July 07, 2015, 07:47:35 pm

You could have a  "Y" lead from the one stick to go to two speed controllers.

It does sound as if the one you have cannot handle the amps required.

Cheers

ken

Title: Re: ESC size
Post by: Time Bandit on July 07, 2015, 09:07:10 pm

Theoretically 30Amps should be sufficient.
Way more than 15-17A on a 540 motor are not "healthy" for it.
If the motors stay nearly cool it seems to me the 30A rating is just a "2 min rating".

I´d get a second ESC of the same kind or a bigger 40-50A ESC. If it´s a "chinese rating" it should probably have more than 50A. Those cheapo 50A ESC of fleabay drop out after 5 mins at 25A  :}

Title: Re: ESC size
Post by: malcolmfrary on July 07, 2015, 09:32:23 pm

Quote from: Time Bandit on July 07, 2015, 09:07:10 pm

Theoretically 30Amps should be sufficient.
Way more than 15-17A on a 540 motor are not "healthy" for it.
If the motors stay nearly cool it seems to me the 30A rating is just a "2 min rating".

I´d get a second ESC of the same kind or a bigger 40-50A ESC. If it´s a "chinese rating" it should probably have more than 50A. Those cheapo 50A ESC of fleabay drop out after 5 mins at 25A  :}

OP said it's an Mtroniks, so it has a real world amp rating.  If the motors are getting hot, they are being overworked, which would indicate that either the props are not as small as thought, or something is tight in the drive line.  Of course, not all 540s are cremated equal - if they are run on more voltage than they are wound and intended for, they will draw a lot more current.

Title: Re: ESC size
Post by: Time Bandit on July 07, 2015, 09:58:51 pm

That´s what I meant, if the motors stay cool or lets say don´t get hot, the rating is maybe not so real world as we might think.

If you put more than 15A through an 540 motor, no matter at what voltage, they are getting hot pretty quick and die pretty quick at >20A.
That´s what Flack needs to find out.
If the motors don´t get hot, get a new ESC.
If the motors get hot, get smaller props or props with less pitch and leave the ESC as it is.

Title: Re: ESC size
Post by: Captain Flack on July 14, 2015, 09:46:21 am

Thanks to all who replied.  I will measure the amps and let you know the outcome..

Title: Re: ESC size
Post by: malcolmfrary on July 14, 2015, 05:34:54 pm

A late thought - if the battery cannot supply enough current, it might be dropping the voltage and causing the radio to "brown out".  This can give much the same symptoms.