Esc vs. runtime

[Sandracer_NL]

All other things being equal (so same motor, same battery, same throttle finger ?, installing an Esc with more Amp capability, let’s say going from a 150A to a 160A or even 200A esc, does it affect runtime? I would say there power would remain unchanged, so maybe only a little less runtime if the esc would be heavier unless a more powerful and therefore cooler running esc would on the other hand improve runtime slightly...
Maybe the experts here know the answer instead of my guessing ?

 

[DoNoHarm]

All other things being equal (so same motor, same battery, same throttle finger ?, installing an Esc with more Amp capability, let’s say going from a 150A to a 160A or even 200A esc, does it affect runtime? I would say there power would remain unchanged, so maybe only a little less runtime if the esc would be heavier unless a more powerful and therefore cooler running esc would on the other hand improve runtime slightly...
Maybe the experts here know the answer instead of my guessing ?

Nah man.

Amps are motor, all motor. If you give it gas, the motor pulls amps. The ESC is at the mercy of the motor. If you have a motor that draws 170 amps, and a 120 amp esc, that motor is still gonna draw its 170 amps when you hammer down, the esc is just gonna get real hot. If you keep that same motor but switch to a 200a esc, it’s still pulling 170 amps, the esc will stay cooler though.


Also take manufacturer amperage ratings very lightheartedly. A hobbywing max8 apparently is a 150 amp esc and a mamba monster is a 120 amp esc, what a joke.

You will save power because it’s not going into heat but it’s negligible.

 

[olds97_lss]

I switched from the blx185 to a max6 with the same motor/gearing/tires and my runtime didn't change, other than I was able to run harder/longer and actually reach LVC before the esc would overheat. But it was marginal.

With the BLX185 and 14T pinion on my outcast with 3.8 trenchers in grass, I'd get roughly 11 minutes before the esc would overheat. With 13T, I was fine until LVC if I didn't try the forward/reverse/forward/reverse to right itself and if ambient was <80F.

With the Max6 and 13T, I could run it like an idiot and reach LVC every time. With 14T, it did fine if I didn't try to right itself.

I still run 14T, but I switched to wrapped backflips and now I can drive as hard as I want until LVC without an issue regardless if I try to right itself or not. Really, I kind of quit trying because it's hard on the diffs... but if it's a long long ways away... and I'm tired... I get lazy.

I have noticed my run times have dwindled though to 12-13 minutes, but I think that is partly due to the fact that I run it harder than I ever did and the lipo's I run are over a 16 months old. When I put in some newer/better lipo's, I get 15-17 minutes.

I run at a grass bmx track mostly now, which tends to be quite a bit of WOT running to hit big jumps.

 

[LibertyMKiii]

If your RC car was geared to 80+ mph then the ESC would see requests from the motor to provide high amperage often. In that scenario a high power ESC would provide the higher amperage and power consumption and thus drain the batteries faster.
People don't see a change because they are not geared this way and rarely have those amperage demands during bashing.

+ what Jerry said below about heat/efficiency

 

[Jerry-rigged]

Heat is power loss, and heating your ESC to 160f while a fan is running on that big ol' heatsink takes some watts. If it is taking 25w to keep your ESC warm, that is about 1 amp for a 6s esc, which would be 300mah-500mah across a 20-30 minute run. I don't see it changing more than a minute or three over a 20-30 minute run, but that is going from 25w to zero. Chances are bumping up a ESC size would more likely change the heating watts from 25w to 15w - enough of a change that the fan can now keep up, but it is still pulling 200-300mah per pack - so you might gain 30 second to a minute of run time, on a half hour run, not really enough to notice.

As a fun side bar, this same math would apply to your motor heat. A hot motor will reduce your run time. Drop the pinion a few teeth, and the motor will draw less load (more run time) and it won't heat as much (more run time), and will heat your ESC less (more run time). Adding a fan to your motor just adds more load (less run time) and lets the motor waste more energy thru heat (less run time). Also, the same gearing that is cooking your motor is adding heat to your ESC (less run time)...

Everything effects everything.