Hot ESC, But Apms Are Below Rating?

[BrianG]

This doesn't really answer your question about the ESC getting hot, but you can set the ESC so it has a more gradual throttle response. This would keep the amperage down somewhat, making the ESC heat less. I changed this setting on mine and didn't notice noticeable loss in power - if anything, standing starts were more controllable. There is also a setting for the types of batteries you have. One setting pulls more current, the other is a little more gentle on the batts. I would think this would also have the effect of slowing down starts and acceleration. Something to think about anyway.

I agree with Gustav; I think it's the heavier load from the grass. The little heatsink on these things are quite small to dissipate the heat required. If you are pulling 115A @ 14.8v, that's 170 watts being dissipated on the controller assuming a 90% efficiency. Frankly, I'm surprised it's just a little hot. Ever feel how hot a measly 75W lightbulb gets after just a few seconds?

Again, this doesn't address your concern about why it's rated for a certain current, yet gets really hot when you draw less. If you can, maybe mount the bottom part of the case on a piece of 1/8" thick aluminum as a secondary heatsink? If it's big enough and you have some type of thermal grease in the joint, it should go a long way to improve temps.