New Speed Control

[Mister_Anderson]

I was checking this for my Rustler. I have a Feigao 6s. Would the controller be able to handle it? The motor doesn't pull full power all the time so it should be able to hjandle it. Just need a second opinion.
Thanks guys,
Chris

[squeeforever]

I think it should, although im not possitive on what kind of amps the 6s pulls, I think it should.

[MetalMan]

It should be able to handle the 6s. Even if the controller did heat up a bit, a fan would fix that.

[Mister_Anderson]

Ok thanks guys. It says on the side of the can 108 amps but that's probably at WOT.
Thanks,
Chris

[MetalMan]

108amps doesn't really mean much. I think it is the current at which the motor operates most efficiently or something like that, but that number should not sway you in any direction.

[Tom F]

If you put 108 amps through a motor then you would have a pool of molten varnish and a short circuit, not a motor.

If you put that much current through a motor it would heat up like nothing else.

Bear in mind that 106 amps would probably be about well over 100W of heat...and if you think about how fast a solderring iron heats up...

Thats probably a stalled current or something

[BrianG]

Let's not forget these motors are essentially AC motors. The heat produced is the result of the resistive properties of the coils. There is also the AC inductive part of the current, which does not cause the heat per se. That 108 amps is the combination of the DC resistance and the AC inductive reactance of the motor. All motors will pull the most amount of current at startup since there is no motion and therefore no back EMF so only the motor's DC coil resistance will limit the current. Once the motor gets going, the back EMF from the changing magnetic field creates back EMF which reduces the current. If a motor pulled 108 amps constantly at say, 14 volts, that would be over 1500 watts. It would take a lot more surface area than the motor can to shed that kind of heat!! Take the lightbulb example; ever feel how hot a 75 watt lightbulb gets? And that has about the same surface area as an XL motor, give or take.

[Tom F]

Ahha, another physics person i see ;)

We were doing about that a few weeks ago lol

[BrianG]

:dft001:

Not physics, electronics, but they do overlap. I just saw some posts that seemed to be leading in the wrong direction and thought I'd throw in my $0.02.

[squeeforever]

Yea, like what Brian G and Tom F said, its only for a split second. Or atleast thats what i think they said....Anywho, pretty much the MAX it will pull only for a split second. I think they rate it so high is so they can cover there ass' incase the motor were to fry a esc.

[Tom F]

Yup i think you're right.

The fact that i was getting 10 minutes would indicate an average of between 20 and 25A - much more realistic

[MetalMan]

That amp draw they put on motors isn't the peak amp draw. I've recorded my 9L pulling more than 85amps peak, and it's only rated at 68amps. My Feigao 12s has also spiked near 85amps, and it's rated at 54amps.

Probably the reason why you won't see very high peaks with the 6s is because the batteries/controller can't handle it. GP3300s or similar can only push out about 100W/cell, and asking for more than 100amps from 6 cells is something that they can't do. If you did have batteries that could take the amp draw and a controller and vehicle that also could, I'm sure that the 6s would pull more than 110amps during peaks.

[Tom F]

Thats a possibility.

Apparently Apogee has some 5000mah LiMn packs in the works, rated at 20C (although the guy has said they are capable of over 150A peak)

[MetalMan]

Tanic has some really good 5000mah Lipo cells out. They are rated at 20C continuous and 30C burst. Only problem is that they're around $60 for one cell!

[Tom F]

Well considerring the obscene ammounts of power you could get, that might not be too bad for low cell count apps