HV Hydro's ESC= Strong Enough?

[BrianG]

Originally Posted by lutach

BrianG,

You and I both know this, but please tell everyone one thing.

How big of a heat sink would we require to dissipate the amount of heat 63V @ 400A would create?

I've seen my share of electric 1:1 vehicles and have found many suppliers that offers anything from 8Kw to over 300Kw and even at 8Kw the ESC or Drive Module has a significant amount of cooling an some goes a far as liquid cooling.

Well, just by playing with some rough figures; ESCs are about 85-95% efficient right? This of course depends greatly on FET slew rate, FET rdson values, PWM frequency, motor inductance, etc, but it should be fairly close. We'll use 95% just to be generous.

Now, let's say the ESC is drawing that 22,200w from the battery as opposed to assuming that power is what the ESC is sending to the motor.

At 95% efficiency, that is 1,110w being dissipated on the ESC (5% loss for the mathematically challenged ). Yeah, that'll take quite the large heatsink.

Of course, what reasonable R/C battery (or motor for that matter) can sustain 400A for any amount of time (and not drop to an unusable voltage)? Not many that I know of without running a 5p+ arrangment.

I would say the 400A rating is more of a sustained burst with a realistic continuous current rating of 200A. Either that, or since this ESC will most likely be used in boats(duh), the amount of time being run is measured in seconds anyway, so they can safely call it a 400A ESC. Either way, run time or duty cycle is short. But hey, it could be a true continuous all-day-long 400A, who knows? If so, could give CC's SHV 200A ESC a run for their money - although the CC will probably be substantially cheaper.

Ok, so I rambled a bit there; time to get back to the math stuff. So, let's say we are running this same 15s ESC at average running currents of 35A for 80% of the time, 150A bursts for 15% of the time (a little accel through bends) and 300A peaks for 5% of the time (heavy accel after corners). Pretty reasonable figures for a heavy vehicle running typical stop-n-go track usage, no? The total average current would be (35A*.8 + 150*.15 + 300*.05) = 65.5A (if I did the math correctly). Optimistically assuming (just to make math easier) we are still using 15s lipo, ESC is running at a constant 95% efficiency (which it won't because of the partial throttle), and the voltage is not dropping under loads (yeah, right), losses on the ESC would still be around 181w. That's still a LOT of power to shed as heat! Ever feel a 60w lightbulb? Now, triple that.

[lutach]

Originally Posted by BrianG

Well, just by playing with some rough figures; ESCs are about 85-95% efficient right? This of course depends greatly on FET slew rate, FET rdson values, PWM frequency, motor inductance, etc, but it should be fairly close. We'll use 95% just to be generous.

Now, let's say the ESC is drawing that 22,200w from the battery as opposed to assuming that power is what the ESC is sending to the motor.

At 95% efficiency, that is 1,110w being dissipated on the ESC (5% loss for the mathematically challenged ). Yeah, that'll take quite the large heatsink.

Of course, what reasonable R/C battery (or motor for that matter) can sustain 400A for any amount of time (and not drop to an unusable voltage)? Not many that I know of without running a 5p+ arrangment.

I would say the 400A rating is more of a sustained burst with a realistic continuous current rating of 200A. Either that, or since this ESC will most likely be used in boats(duh), the amount of time being run is measured in seconds anyway, so they can safely call it a 400A ESC. Either way, run time or duty cycle is short. But hey, it could be a true continuous all-day-long 400A, who knows? If so, could give CC's SHV 200A ESC a run for their money - although the CC will probably be substantially cheaper.

Ok, so I rambled a bit there; time to get back to the math stuff. So, let's say we are running this same 15s ESC at average running currents of 35A for 80% of the time, 150A bursts for 15% of the time (a little accel through bends) and 300A peaks for 5% of the time (heavy accel after corners). Pretty reasonable figures for a heavy vehicle running typical stop-n-go track usage, no? The total average current would be (35A*.8 + 150*.15 + 300*.05) = 65.5A (if I did the math correctly). Optimistically assuming (just to make math easier) we are still using 15s lipo, ESC is running at a constant 95% efficiency (which it won't because of the partial throttle), and the voltage is not dropping under loads (yeah, right), losses on the ESC would still be around 181w. That's still a LOT of power to shed as heat! Ever feel a 60w lightbulb? Now, triple that.

Thank you BrianG, you sir are my professor lol. Now let me explain why I asked that. I've been telling a few people, I like to treat what ever rating a ESC is built for as what it'll do for a spike (That hard acceleration on start ups and out of a corner). Let me use my 200A 1/10 scale ESC as an example. I use the 200A rating as a measure of the burst it'll handle. I got 178A burst out of it and snellemin has reached 182A. Now my 6S, 10S and any other ESC should be treated the same way so everyone won't get disappointed when their ESCs burned up because they were trying to get 100A+ continuous out of their ESC. I hope all the manufacturers who states a number that is out of this world would promote this to keep this hobby fun and safe. Thank you BrianG for your professional answer.

Regards.