Wednesday, July 20, 2011

Power play

We are now having some good flying weather so I went flying again.  Now I had some issues with the throttle.  I started experiencing the typically reported Wild Hawk speed controller issues with the power cutting out and coming back on.

In reviewing all the reported issues I could find on the Internet, I could not find solutions that did not include replacing the speed controller and motor.

Well I started reviewing all the facts.  The speed controller is set to shutdown the motor when the battery voltage drops below a certain level.  I'm using home made 3 cell series li-ion battery pack.  I found that the batteries I am using (18650 series) have a max discharge rate of about 4 amps (~2C).  One of the cells in the pack shows a slightly lower voltage than the others.

with this info, I think I can say that what is going on is that with this battery the motor is pulling more than it can supply so the battery is compensating by lowering it voltage.  This voltage drop tells the speed controller to shut down the motor and only supply the servos.

I tested this by hooking up a battery monitor to the charge connector and then ran the motor through various speeds.  Sure enough, after a bit, especially at high speed, the battery voltage dropped and the motor started stuttering and finally shut down.  Interesting enough, I noticed that the speed controller got really hot.

Any way, the next time out I used the NiMH battery and flew for a long time and had no issues.  Problem solved?  Now I'm looking for a real LiPo pack for the more power and run time I was looking for.

Thanks for stopping by my blog and please post comments, good or bad.  Be sure to come back and check for future posts.

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Mr. Clean