I bought a Chevy Volt Gen1 DC-DC Converter - Now What? Topic is solved

[mjc506]

Ahhh bugger. Amazon? Or get hold of an Arduino Due?

[Gregski]

Ahhh bugger. Amazon? Or get hold of an Arduino Due?

yup, I got an Arduino Due and SaavyCAN works fine on that, I am trying to get it working on Teensy to show folks how it works on there type of thing, plus I like pain

[mjc506]

Ah, good to have a working system to compare against

Just a thought, have you got Teensyduino installed? (The Arduino IDE that's been "teensyfied")

[Gregski]

Ah, good to have a working system to compare against

this is actually worthy of a discussion or comment, I feel like to really make it headache free you need a dedicated computer or laptop just to a platform because all these microcontroller boards and Arduino sketches totally conflict with one another, I am constantly pulling this library out and putting this one in when going between Damien Maguire's Lexus GS450h VCU (which I luv by the way) and my UNO to talk to my ISA current shunt, to the DUE for CAN Busing and the Teensy for SimpBMSing, anyone else experienced this? I think I saw Damien with multiple laptops in a couple of his videos.

Just a thought, have you got Teensyduino installed? (The Arduino IDE that's been "teensyfied")

yes and got it working with Tom de Bree's SimpBMS

[arber333]

DOH! I will have to learn all the new systems now!!!

[mjc506]

Things do seem to be more stable on Linux, but that's another thing to learn, so... I would have expected everything to play nicely though, just have to change the 'board' each time you swap projects. But yes, library conflicts can be a pain. Although, once you've got each board programmed, they should just talk over serial (ie, you don't need to even have the Arduino IDE open to use Savvycan, and Arduino set to compile for a Due will happily talk to an Uno over the serial monitor for example. Or you could even use another Serial terminal. Apologies if I'm teaching you to suck eggs...

[Gregski]

so I've been beating up on the Chevy Volt first gen DC-DC converter in a companion thread called: I think I CAN, I think I CAN... but I want to share some highlights in here as well from what I learned

first here is how to check the polarity ie figure out which wire is positive which one is negative

no light so polarity is correct

[Gregski]

and here is something I learned, GM crossed the wires in the intermediate cable running from the converter to the battery pack

[Gregski]

here's a close up

[Roadstercycle]

Hi Guys,
Been a bit since I've been here. I've been using the Chevy volt Gen 1 DC-DC converter on 3 of my builds. I use a Teensey and 1 line of code to run them. Very simple. Here's the code. I believe I set it to 14.0 volts. I'm on vacation so I can't verify at the moment. The charger is hooked up all the time with no relay, I just turn power on to the teensey and the DC-DC with ignition or when the J1772 is plugged in to run water pump and cooling fan.

Happy Charging!


#include <FlexCAN_T4.h>


const int ledPin = 13;

FlexCAN_T4<CAN1, RX_SIZE_256, TX_SIZE_16> Can1;


void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
pinMode(ledPin, OUTPUT);

Can1.begin();
Can1.setBaudRate(500*1000);

}

void loop() {
Can1.events();
static uint32_t t = millis();
if ( millis() -t > 4 ) {
CAN_message_t frame;
frame.id = 0x1D4;
frame.len = 2;
frame.buf[0] = 0xA0;
frame.buf[1] = 0xB1;
Can1.write(frame);




t = millis(); // reset 5 second counter
}

if ( millis() -t > 4 ) {

Serial.print("CAN1 ");
Serial.print(" ID: 0x");
}



digitalWrite(ledPin, !digitalRead(ledPin));

}

[Gregski]

well it's been forever and a day since I played with this stuff, but I am finally ready to hook up the DC DC converter on my truck and was wondering if anyone has gotten it to work with a Teensy in a real world example, and since so much time has passed did they ever come out with a Teensy with a built in CAN Bus transceiver on it for compactability

and I know I have been out of the Teesnyduino game for a minute, but tell me this is wrong and they just forgot a decimal

[Zieg]

Has anyone had issues with the output from these things fluctuating? I have the later version of the gen 1 and noticed the other day that my headlights and tail lights are flickering while it's running. No flicker when they're just running off the 12v battery. Wondering if mine is defective and I should go search for another, or maybe slap a big capacitor on the output and hope for the best?

Also if it has gone bad, I wonder why. I have it mounted in my transmission tunnel so it does see airflow from the bottom of the car, but probably not a ton, and not necessarily over the fins. Might be prudent to build a little scoop and duct some air to it..

[Zieg]

...

Just adding to this.. I did find another one for a decent price, but it's doing the exact same thing. I suppose they could both be defective, but it would be nice to get confirmation whether others experience this or not. When I installed the new one I also redid all of the HV and LV wiring, so I think I can rule that out. Tried connecting a much larger 12v battery and even a 22,000 uF capacitor but it didn't change anything.

I'm assuming this isn't affecting any of my electronics since they will all have filtering on their input power supplies, so the headlights and tail lights flickering is probably the only symptom?

[arber333]

Just adding to this.. I did find another one for a decent price, but it's doing the exact same thing. I suppose they could both be defective, but it would be nice to get confirmation whether others experience this or not. When I installed the new one I also redid all of the HV and LV wiring, so I think I can rule that out. Tried connecting a much larger 12v battery and even a 22,000 uF capacitor but it didn't change anything.

I'm assuming this isn't affecting any of my electronics since they will all have filtering on their input power supplies, so the headlights and tail lights flickering is probably the only symptom?

What speed is your CAN command running at? Maybe it flickers because its not receiving signal at regular intervals as it expects.
In that case it will go from 14V (commanded) to 13.2V (default) in the interval your CAN gets the msg through. DCDC expects command in 100ms period.
Also you can test my thesis if you just send several CAN commands and then stop sending them. Then output should go to 13.2V and keep that level.

[Zieg]

Hmm, interesting thought. My BMS is sending the can message and it's pre-programmed to control the gen 1 dcdc, but I don't know what the interval could be. I should be able to temporarily power down the BMS and see if the flicker is still there when it's holding 13.2V. Good idea, thanks!

[arber333]

Hmm, interesting thought. My BMS is sending the can message and it's pre-programmed to control the gen 1 dcdc, but I don't know what the interval could be. I should be able to temporarily power down the BMS and see if the flicker is still there when it's holding 13.2V. Good idea, thanks!

Can you change CAN rate with your BMS? Not speed, DCDC CAN speed should be 500kbps. But rate should be about 100ms.

[Zieg]

I don't believe so. If the rate turns out to be the problem, I think I'll have to transfer the task of sending that message to the Teensy 4.1 that I'm using as an interpreter between some other devices on the network.

[arber333]

I don't believe so. If the rate turns out to be the problem, I think I'll have to transfer the task of sending that message to the Teensy 4.1 that I'm using as an interpreter between some other devices on the network.

Teensy 4.1, that would be a good MCU for CAN translator. I use one for a complete VCU in Mazda. You simply need a 12V signal from your key to signal Enable state and it will send CAN traffic in correct order. If you need the code i can provide .

[Zieg]

That's okay, thanks. I already have a handful of messages programmed into it for Foccci, so adding one more isn't a problem.

It's actually a bit tempting to do this anyway. The BMS doesn't know the state of the contactors so it starts the DCDC as soon as the key is on. That always scares me a bit because it draws its power through the precharge circuit until I press the start button.. If I use the Teensy I can have it check the inverter's OPMODE before starting the dcdc.

[arber333]

That's okay, thanks. I already have a handful of messages programmed into it for Foccci, so adding one more isn't a problem.

It's actually a bit tempting to do this anyway. The BMS doesn't know the state of the contactors so it starts the DCDC as soon as the key is on. That always scares me a bit because it draws its power through the precharge circuit until I press the start button.. If I use the Teensy I can have it check the inverter's OPMODE before starting the dcdc.

Or you can have dcdc wait for like 2s and then observe voltage to be sure... I think dcdc puts out status of da bus...

[Zieg]

True, I think it does - but it might not be able to tell the difference between getting power through the precharge circuit or not. If I turn the key on and don't press start, it will just sit there with the precharge relay closed indefinitely. I guess I could try to decode the voltage output and see if it reports lower than my minimum battery voltage? Then I could only kick it on if reported voltage > some threshold?

[arber333]

True, I think it does - but it might not be able to tell the difference between getting power through the precharge circuit or not. If I turn the key on and don't press start, it will just sit there with the precharge relay closed indefinitely. I guess I could try to decode the voltage output and see if it reports lower than my minimum battery voltage? Then I could only kick it on if reported voltage > some threshold?

Do you use any other CAN device that outputs HV on the line? Like inverter... Maybe use that...

[Zieg]

Well yeah the inverter is on the same network, but that's why I was originally thinking I would just have the teensy check OPMODE. The inverter controls the precharge and + contactor anyway.

[arber333]

Well yeah the inverter is on the same network, but that's why I was originally thinking I would just have the teensy check OPMODE. The inverter controls the precharge and + contactor anyway.

So command explanation is like this...
CAN command 0x1D4 A0 B2 in 100ms period
byte0 A0 requests DCDC power ON, to signal DCDC OFF just send 00
byte1 B2 would mean 14V and likewise AF means 13,8Vdc

The output voltage setpoint that the DC-DC is to regulate.
The scaling seems to be [Voltage] * 12.7. For example, to command 13.8V, you would send 13.8*12.7=175=0xAF

[Zieg]

Perfect, thanks. I just tested letting the BMS get it running and then stop sending messages. I could tell the voltage dropped from the 14.x volts setpoint, and the flicker went away!

I'm surprised the BMS was apparently not sending the messages often enough, since it's one of the few dcdc units they advertise as being compatible. Really glad you had me check that! Next I'll add the message to the teensy.. and then if all goes well, I guess I have a spare for sale. Haha.