Re: ADC A89 specs

[Colin Dedman <cjd121@rsphy1.anu.edu.au>]

jerry dycus wrote:

>    Hi Lawrence and All,
>        I was hoping you will bring the bike up to
> speed with the controller then short out from the pack
> b+ to the motor + .  If you gain more than a couple of
>  mph the controller is limiting you.

This is true but there are probably easier ways. A voltmeter wired to
measure voltage drop across the controller tells you the same thing.
This a  275A controller I believe, and I would have thought that the
"fully on" voltage drop would be negligible under normal conditions,
remembering that the rated motor current is only 100A or so. Does anyone
know the "on" resistance of a  1204 36-48V Curtis 275A controller?

>
>                                     Another way is 2
> or 3 selenoids with 1 or 2 resistors for starting. 1
> more selenoid for saftey cutoff inline with the others
> and a fuse and you have a full controller. The
> resistors are not on long so don't use much power.
> This controller will be higher proformance than your
> curtis . Cheaper and easier to repair too. A low power
> vehicle like yours is 95% of the time either on or off
> anyway.

A primitive controller as you describe is indeed cheap, simple, easy to
repair, and does actually work. To say it is a "full controller" with
"higher performance" than the Curtis is stretching things a bit though.
The PWM controller can smoothly and continuously control effective
voltage from zero to maximum, with very little loss. A switched resistor
arrangement cannot. Under "full on" conditions a relay has a slightly
lower "on" resistance, but this should be negligible with a correctly
sized controller. I strongly dispute that the controller will (or
should) be fully "on" 95% of the time. With a controller such as you
describe there will indeed be a strong temptation to switch out the
(wasteful) starting resistors and switch the motor direct across the
battery. The result is very large motor current until the vehicle gets
to near top speed, and consequent high dissipation and poor efficiency
from the motor. The relay that switches the battery straight across the
motor runs cool at the expense of the motor running hot. You need to
analyse overall motor+controller efficiency , not just apparent
controller efficiency. With your controller you are either "flat out" or
burning up power in a series resistor - they are the only choices you
get, and neither is an efficient way to operate. A PWM controller is far
superior, enabling the motor current to be precisely controlled at all
times, without burning up power in a series resistor.

Regards, Colin