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Oversizing BL ESC

Old 10-09-2005, 03:37 PM
Jessum Dumguy
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Default Oversizing BL ESC

Hello All,
Hoping the Electrical GURU's can answer a rather
odd question about Brush-less ESC's.
Please forgive me if this is answered somewhere already,
I've been searching and reading for several hours already and
nothing I've read answered my SPECIFIC question.

So Okay Here goes, Is there any proformas HIT ( Discounting Size and Weight ) in using
a Oversized ESC?
(ie) Running a itty bitty 10 amp outrunner on 3 cell Lipoly with say a
90 amp ESC like say Hacker Master series 99-3p opto BL ESC?
( I told you it was an odd question )

Obviously the example above is a bit extreme but the question is
one of capability not logic or common sense. What I was wondering is,
Will the low amp draw effect the performance of the ESC's abillity to
effectively control the motor?

Anyway thats my silly question of the day, My need for understanding.
Jessum Dumguy
Old 10-10-2005, 08:21 AM
Walt Thyng
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Default RE: Oversizing BL ESC

I'm no E.E., but my experience tells me that the answer to your question is "No." Now, I've never taken it to the extreme of your example, but I did test Speed 400's using an Astro 204D controller with no problems. The caveat would be that the Astro is an older design; maybe the more sophisticated Hacker would react differently.

Pop over to Wattflyer and ask your question in the Power Systems forum. I know you'll get the right answer there.
Old 10-11-2005, 12:14 PM
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Default RE: Oversizing BL ESC


You are going to get a lot of answers to your question in theory! All the calculations and background will give you a BASIS for the ultimate design. In actual use, try to acomplich a ballance in the system that will not produce a lot of heat. The ballance includes your left thumb also. If you are 3-D flying and keep the session in a hover position, the overall demand of the system is high. You are not going to damage the motor or controller, but may kill your battery from high power demand. A controller engineer from Phoenix advised me to use the largest controller I can stuff into the plane without a weight penality. Many of the cheaper motors produce a lot of heat, and thus higher demand from the controller and battery to stay up with the better motors like AXI and Hacker. Sorry, there is no substitute for efficency and quality that I have been able to find. Spend the money for good motors, make sure the controller has the ability to provide the total power demand of the motor, prop correctly and keep the wide open time for when you need it. Good combos are AXI 2212, 25A phoenix and TP 1320 3S battery, prop 9 or 10 X 3.8 apc. Great combo, Hacker 20-22L, hacker 20A controller TP 1320 with 11 X 4.8 apc prop. Both hover my 17 oz rcx planes Illusion and Extra 330L at below 1/2 throttle, with very little temp. increase over ambient, 15-17 minutes flight time. Both systems could fry the battery from high demand if not flown with some reason. A watt meeter is a must have item as much as the battery. When flying, make a effort to keep the speeds and demand down, your flight times will increase and your systems will keep on trucking. Without overall ballance, you can and will kill any weak link within the overall system. Keep your prop pitch down to 4.8 or 3.8 and adjust lingth to reduce amp power draw. If motor max draw is 20 amps and controller is 18, it will work until you open it up for more than a few seconds. The controller will always be on the hot side as it is borderline. A 25A controller would run much cooler and all in ballance. When you add gearing to the total system, it is again a whole new world. I perfer the outrunners with enough power to pull the prop without gears. Gears are a constant pain, noisy and high maintance, but will let you run a smaller and cheeper motor to achieve the desired power. For me its tough enough to get the brushless motors right without adding gears into the problem. Why put up with the expense and frustration of development when you can go to dealers like rcx that guanante your SATISFACTION. Not many out there but the ones that are deserve our backing. Have had good luck with Thunder Power so far, nothing but problems with Apogee and Kokum living beyond a few charges. Enjoy!

Stupidity has a price that is always paid.
Old 10-17-2005, 11:49 AM
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Default RE: Oversizing BL ESC

I use both Kokam and Thunder Power and have had NO problems with either.

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