sal37

My PNP Mini Ultra stick has a motor surge at full throttle. Basically it sounds like its cuttting in and out really fast, rpms coming downand back up. Only happens at WOT. I am using an old lipo out of a parkflyers edge 540. Its an 1800 Mah 3 cell lipo. Could the new plane and motor be surging becuase the discharge rate of the old battery is too low?
Thanks,
Sal

Fliprob17

That is a possibility, do you know what the C rating of that battery is Ex: 15c......that way you can find out how many amps it can dish out to the motor. Take your 1800mah rating divide it by 1000 to get amps.....so 1.8, then multiply it by your C rating to get battery amp delivery or discharge. Then compare to what your motor needs. I would guess you are using an E-Flite Park 450 890kv Outrunner in that MUS, so your motor should be 14 amps continuous and 18amps burst. It is also possible that the battery has just seen better days

sal37

Not sure but I think it is 10C. Its actually from an Art Tech plane.

stinky

Could be you end point adjustment on the throttle. You don't say which speed control your using so I can help that way. But if its a Castle and your throttle setting is program auto you need to keep the throttle at WOT for 2 seconds for it to program you need to do this each time you connect the battery. If you use the other throttle option you won't need to do this each time. Also with CC ESC if the battery can't provide the amps it will surge and search.
steve

sal37

thanks both of you. Its the e-lite 25 amp esc. Seems t be getting slightly worse each flight. One way to find out, buy another Lipo.

Sal

Matt Kirsch

My Feedback: (21)

1800mAh at 10C is only 18 Amps. That's the maximum limit for the Park 450 motor, and I've got to presume that the included 10x7 prop pushes the motor to draw at least that much.

When battery manufacturers give you C ratings as "continuous" they don't mention that that rating is derived with perfect cooling, and at the cost of shorter flights and reduced battery life.

In short, you're almost certainly pushing the battery too hard, and the surging is actually the ESC's low-voltage cutoff telling you that there is a problem.

sal37

Thanks Matt,

Actually I am using a 12x6 prop so I assme its drawing even more. Makes sense what you say about the surging and the low voltage cutoff. At least the money I am about to spen on my battery will make a difference.

sal37

Hi Matt,

Just wanted you to know you were right about the ESC low voltage cutoff. As a test, I switched it to 2 cell cutoff and the surging went away. I'll have to get a new battery.

Sal