Mike Malmberg wrote:
Thank you Lee and Roland, I deployed a resistor and capacitor as you
described and it works perfectly,
Excellent! I'm glad I could help.
I thought I would ask again for any explanation on how the 0-5k pot
works on the zilla to increase voltage (counter-intuitive)
and how does the BMS affect that by reducing voltage?
I have a Zilla, but it has the hall-effect throttle option. My knowledge
of how the Zilla works with a 0-5k pot is limited to what I read in the
manual. And I know nothing at all about the Orion BMS. But maybe I can
provide some general guidance. The standard arrangement for EV
controllers that use a 0-5k pot box is:
- Minimum resistance = minimum speed.
- Maximum resistance = maximum speed.
- Shorted pot wires forces the controller OFF.
Actually, any resistance under a few hundred ohms is off.
- Open pot wires also forces the controller OFF.
Actually, any resistance over about 4500 ohms forces it off.
The circuit inside the controller is measuring the potbox RESISTANCE;
not voltage. There are some special controllers that do measure voltage,
or that have different resistance-versus-speed behaviors, but they are
not very common.
Now, there are lots of ways the controller circuit can measure the
potbox resistance. It can apply a voltage, and measure the resulting
current. It can apply a current, and measure the voltage. It can create
an oscillator, and use the potbox resistance to determine the frequency.
You need to talk to someone very familiar with the design of the
controller (like Otmar Ebenhoech for the Zilla) to get an accurate
answer on this.
But, it's not really necessary that you know. It's only necessary that
you set up your Orion BMS to change the *resistance* across the potbox
terminals to limit the motor speed.
Did you say the Orion BMS has a relay that it turns on if any cell's
voltage is low? If so, then you can use the contacts of that relay to
switch a resistor in parallel with the potbox. If this resistor is 5k
ohms, then:
- With the relay OFF, the 5k is not connected. Your potbox has
the normal 0-5k range, and you have 0-full throttle.
- With the relay ON, there is a 5k resistor in parallel with the
potbox. This reduces its resistance range to 0-2.5k.
This in turn limits you to half throttle.
The Zilla also has a lot of programmable options. You can set it to cut
back on the throttle, or even prevent you from driving if the total pack
voltage falls under X volts. This is another way to keep from destroying
cells if one goes dead.
--
Anyone who has never made a mistake has never tried anything new.
-- Albert Einstein
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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