Lithion-Ion Batteries

[ToddF]

Originally Posted by JVN

This is the first time I've seen brushless motors suggested as a cost saving measure. Do you have a rough BOM of what you'd put in the kit spec'd out with pricing?

-John

I'll take our shooter from last year as an example. We used a pair of RS-550 motors ($7.25 ea) driven by a pair of Jaguar drives ($119 ea), for a total of $252.50 system price.

That motor is 36mm in diameter, has a Kv of 1608 rpm/V, max current draw of 85A and max power of 254 Watts.

For an apples to apples comparison, Hobby King has a 36mm diameter brushless inrunner (S3674-1660) for $39.20 each. This motor has a Kv of 1660 rpm/V, a max current draw of 60A, and max power of 1600 Watts.

To drive it, we would need a 60A ESC. The HobbyKing Red Brick 60A ESC is $13.20 each. This ESC is a fraction of the size and weight of a jaguar, though it is controllable via PWM only.

So, using the motors and power drivers mandated by last years rules, we had a total of 508 Watts of power available at our shooter wheel for $252.50 total cost. If we were allowed to use brushless motor technology, we could have had 3200 Watts of power at our wheel for $104.80 total.

More power, less weight, less than half the cost. Note that the real driver of the cost difference is the drastically lower cost of the drive electronics. They can get that cost so low by removing all the smarts from the controller and making a bazillion of them. I wouldn't want to eliminate Jags and CIMS altogether, just allow these better technologies as an option for use where appropriate.