ESC Help
 

I don't think I fully understand ESC's, not sure if anyone really does, but if they do could they take a minute and help me out.

I am getting a plane, which calls for a 35A Airboss ESC, well they are horribly overpriced and I am looking at Thunder power ESCs...

My question is does the ESC have to be able to handle a burst from battery. (i.e. If battery says burst of 40C and my ESC says it can handle 35 on burst.) Would the ESC break down and would I see my beautiful bird fall like a rock from this example I gave?

Now, if the plane calls for a 35A Airboss then it should be able to use a 40A Thunder power one right, and if it is too big of an ESC am I wasting battery power?

I am horribly confused,

Thanks in advance for any information you guys give.

RE: ESC Help
 

The motor is where it starts. A motor mfgr. gives guidelines as to how much currant it will accept before damage from excess heat occours. A motor designed to run 30 amps constant with burst of 40 amps for 10 seconds should be propped to not excede those guidelines. The prop makes the load for the motor. So you get a SC designed for 30+ amps, the correct size prop, the battery that gives you a proper run time. Doesn't matter at all how many amps the battery can produce if the motors load is correct. Too large of a prop will make the same setup go way past safe specs.

RE: ESC Help
 

Your motor and prop selection will determine the your max current draw. If the plane manufacturer specs a 35A ESC, then you should be sure to choose a battery pack capable of at least 35A continuous, and another ESC capable of at least 35A continuous. The amp draw specified for the ESC and battery are simply max values, if you exceed those values you may fry your ESC/battery. Getting an ESC and/or battery pack rated higher than 35A is probably not necessary, but it will give you some margin, and they'll probably run cooler.

RE: ESC Help
 

Hi Jug.

I hope to not confuse you more with my answer, I'll try to do it as clear as possible it's 3:40 AM. [sm=tired.gif]

NO, the ESC will not break down if the battery has a given cont number and a high burst, the ESC will handle it. The battery is like a portable storage that hold the power until the ESC ask for it. How much and how fast will release this power with out overheating it's set by the C number that the company give. C = one time the capacity of the battery and the number before it will tell you the discharge rate of the battery by multiplying the mah by the number. For example: a 2100 mah lipo has a C of 2100 so if the rating is 15C cont then the max A ( amp ) will be 31.5A ( 15 x 2100 = 31500 ). Since 1000mah = 1A then 2100mah = 2.100A we do the matt again 15 x 2.100 = 31.5A . The max burst is set for 15 sec this will be 24C once again 24 x 2.100 = 50.4 round it to 50. When you go for setting your system go by the cont rate and not by the burst rate.

Now with the ESC you always can go with the recommended 35A or go at least one bigger than suggested 40A will not hurt, only in weight if you are counting every gram. Now think of it like the gas pedal of a car the more you press it the faster or more power the car get. So the more throttle you give on the Tx the more power it will draw from the battery and pass it to the motor. That’s where the rating come in auction by giving you the maximum amount of Amps that your ESC was set to work without danger of overheating. The same goes for the motor when it received. So going back to the example if you have a 35A ESC the battery will be ok since the cont A will be 31.5A. As long as you don't keep full throttle all the time because the ESC will draw 35A from the lipo and that's more than 31.5A but as long as you do small burst you can go as much as 50A and that’s more than the 35A. Same for the motor receiving it.

Just make sure you have a balance in the system your going to use. If you go with the recommended or bigger ESC that's ok as long as you keep a good throttle management so you don't overamp the system. This number can be affected by a few factors so you have to keep in consideration. One is the prop size like the other members already told you. A bigger prop will find more resistance with the air causing the motor to work harder so it will need more amperage to perform, in return can cause overheat to any or all parts of the system. The second will be cooling, is you don't assure a good flow of air trough the system ( Lipo, ESC, Motor ) it will cause the heat to rise faster specially when the rating is lower or close to the limit, with bigger rating it take longer to heat.

Hope it help.

Fernando

RE: ESC Help
 

Thank you so much Fernando, that did help clarify some things I was still wondering :D

RE: ESC Help
 

Hey no problem that's why we are here for, we all help each other. Any other question just ask.

Fernando