leftyb

I am having a difficult time in trying to determine the size of an ESC, in aphmeres, based on the motor size and battery configeration. Is there a simple formula or method to make this determination? Also, how much greater, in amps, can the ESC carry above the estimated draw? For example, can an ESC rated at 30 amps be used for a system estimated at 15 amps, or would you even want to?
Thanks for any suggestions.

Time Pilot

Think of an ESC like wiring. You can use heavy duty cables to carry light loads, but put some small wire on a large load and watch the fireworks.

A more capable ESC can handle lighter loads.

As far as how to determine loads, you can go to the GWS site and browse their tables. Start here.

http://www.gws.com.tw/english/produc...owersystem.htm

You can use a online program like P-calc too.

http://brantuas.com/ezcalc/dma1.asp

leftyb

Thanks for the response TIME PILOT. I will take a look at the sites you indicated and see if that solves some of my questions.

Dr Kiwi

The size of ESC required is determined by the current your motor will draw, with your prop and gearing, from your battery. You, first, need to measure or otherwise calculate the draw your set-up will achieve, and then select an ESC with a current rating above that. Most ESC's have two ratings given - one for continuous, the other for very short term bursts. ALWAYS err on the side of caution - there is no harm in having a higher rated ESC than you need (the only downside will be that the higher rated the ESC, generally, the heavier it will be).

Brushed motors need brushed ESC's, brushless motors need special, generally more expensive, brushless ESC's. If you use Lipoly batteries you should get an ESC which has built-in or programmable LVC (low-voltage cut-off) to save your packs from over-discharge. Castle Creations with their Pixie (brushed) and Phoenix (brushless) are among the leaders here, though Jeti and others also make suitable ESC's.

Hope this helps.

Cheers, Phil

Matt Kirsch

My Feedback: (21)

The key here is in figuring out the Amps. It's not something that you can plug into a simple formula on a calculator, or do on a sheet of paper. You've only got three choices when it comes to figuring out Amps:

1. Measure with an Ammeter, Astro Whattmeter, or similar device. Obviously, this can sometimes be a chicken-or-egg situation, especially with brushless controllers. You can't measure the current without an ESC, but you don't know what size ESC to buy until you measure the current...
2. Program the components into a "calc" program like P-Calc or Motocalc. These will get you in the ballpark most of the time.
3. Use the manufacturer's application tables, if they have them.

Worst case scenario, get a controller that can handle the motor's maximum rated current.