Paul & Sabrina's cheap DIY 144v motor controller

[duncan]

Hi Articus
DO NOT connect the M- to the chassis or vehicle ground!
NOT NOT NOT

The main battery should be isolated from the chassis - always!

It's OK for the 12v system to use the chassis but NOT the high voltage traction battery

[MPaulHolmes]

Ya! What Duncan said! The motor has M+ and M-. M+ is the same as B+. B- is the battery pack minus. M- is not the same as b-. So they call it m- because it's the negative terminal of the motor.

[Articus]

Ooops yeah not sure why I said that. I realize that M- is the PWM modulated B- so they are not the same. And connecting M- to chassis ground would have blown up my 12V battery?

Is it a good idea to permanently attach a discharge resistor *edit* across the capacitors?

Also I converted my controllers to Hall effect inputs. I wanted to see what happened when the throttle sensor shorted to ground, shorted to power, or just open circuit.

Short to ground isn't a big deal. Short to power can give trouble but can play with the t-fault-max-rc and actual pedal throw to get that correct.

However I had RTD explorer open and when I disconnected the 0-5V throttle input, I watched the throttle on RTD explorer drift up to about 250 counts. That's not good. How can I treat that situation where there is an open circuit break on the sensor input to the Revolt.

[MPaulHolmes]

If you add a Ohhhh, 100kOhm resistor from the throttle A/D to ground, it should take care of a disconnected throttle.

[Articus]

Ah ok thanks! So when I originally converted I followed Jack Bauer's instructions. That was to link out R8 and D1 with wire links. Remove R10 completely. Looking at the circuit diagram, which I don't completely understand, can I actually just put the 100kOHm resistor in location R10 on the board?

[Articus]

That worked thanks Paul. Now is there number off the top of your head that you can give for the isolation voltage between the 12V battery connection at the controller and the tractive system voltages going through it?

Thanks

[MPaulHolmes]

The DC-DC converter that provides the isolation is rated for 3,000V for one minute.

[jedsmd]

And connecting M- to chassis ground would have blown up my 12V battery?

Articus
I think the main concern is it would create a high voltage safety hazard.

If the battery pack is grounded to chassis and you touched a battery terminal while leaning on the car you could get nailed. Also if you used a metal wrench on a battery terminal and it touched the chassis it would short out part of your pack (with spectacular results ).
Jerald

[Articus]

What sets the current reference parameter that I'm seeing in RTD explorer?

I noticed when I was testing with a little 12V DC motor, the current reference was setting itself higher than that of the bench power supply I was using (5 Amp max) and probably a set point that would destroy the little motor. When I pushed the throttle a small amount I had no real throttle control because of this. I guess because the current feedback was much lower than the current reference (which is higher than possible), the PWM got sent to 100% in vain attempt to get them to match.

[jedsmd]

Articus
Have you built the power section? If not what are you using to drive the motor?
Jerald