Explain how RC ESC's are so small for their amperage

[harrisonpatm]

I am briefly dipping my toes into the DIY flying drone building world, and one thing is bothering me, based on my current knowledge of larger e-vehicles: How are these tiny controllers capable of powering not one, but 4, BLDC's at 30-50 amps each? Based on reviews it seems like they actually are capable of their rated specs (at least the name-brand controllers). But they're either 20mm or 30mm squares, absolutely tiny!

Here's a generic board-only bldc controller that I picked off amazon at random, only about 20A capable. It's 63x43mm

Here's a well-recommended drone controller, controls 4ea bldc's, 50 amps each, and it's only 38x41mm

If I had to guess, I'd say the two main factors are that drone's operate on lower voltage (rarely over 6s Li-Ion for hobbyists, while ebikes range in 7-14s for example), and that they only are expected to run for 10-30 minutes at most. Some small ones are only rated for like 4-10 minutes run time.

Are we in the electric vehicle community missing out on something?!? Lol

 

[Hillhater]

Are we in the electric vehicle community missing out on something?!? Lol

No,… RC ESCs have been tried and used successfully on some Ebike builds, but there are reasons they are not popular.
only a few (Castle electronics HV series), were found to have suitable specs, performance and reliability , but that came a a high cost.
Equivalent commercial high voltage and current controllers became available at lower costs, and motors like the Bafang and Tonsheng have internal controllers .
many attempts and tests were tried with alternative high power RC controllers, ( Alien Power etc), but few passed the tests.
Then other custom developed controllers ( vesc etc) started becoming available to overcome the issues with the RC units.

 

[amberwolf]

No, not missing anything.

They can usually only run that power for very short runtimes, or with really good cooling, etc.

Notice that most of these are very low voltage, so high current doesn't mean high power.

They also generally can't handle high startup loads--they don't have the margin for the extra current / heat peaks--most of them are meant to startup propellers or lightweight land or water RC's. People used them on ebikes for RC motors in the racing-track days a decade or so ago and blew them up....

Notice the drone controller linked is for a hand-sized drone like the below (note size of drone relative to XT battery connector)

 

[DanGT86]

I think traction is a huge factor. Current spikes occur in fractions of a second. A propeller slipping through air or water will only cause massive peak current draw for brief fractions of a second. An ebike accelerating to max speed might hold peak current for 20seconds.

As control hardware and programming has gotten better in the VESC for example, the size of ebike capable RC style controllers has gotten smaller.

I always thought of RC controllers on ebikes as if they were F1 cars. The power to weight is high but everything is right on the edge of disaster.

 

[Hillhater]

many attempts and tests were tried with alternative high power RC controllers, ( Alien Power etc), but few passed the tests.

For anyone keen to relive the experience, ..this is a link to the long running thread on the testing of thr Aliens 24s (90+v) , 420 amp , RC ESC.
(probably save time by starting at page 28 and work back !)

420A 24S ESC by aliens

Spotted these on eBay. Alien Power Systems. Controllers are for RC, but are supposed to work on bikes too. PC interface for settings. I can supply 200, 250, 300, 350 and 400A, with a battery voltage from 2 to 24s Li po, with firmware for heli, boat, car or e-bike, and cooling system for air...

endless-sphere.com

 

[nicobie]

People used them on ebikes for RC motors in the racing-track days a decade or so ago and blew them up....

Thud was able to keep his motors/controllers together it was the 2 speed gearboxes that were needed to match the motors specs that would blow up. It was the first time the gas bikes saw what a ebike could do.