GM / Chevrolet Volt Gen2 DC-DC converter

[ggeter]

Did we get an answer on this? I'll be using this unit in my project and would make things simpler.

[arber333]

Yesterday i installed my Volt Gen2 DCDC in my Pug and i supplied it with 12Vaux battery and HV. I used 5V pwm signal from my DUE board and set it to 110Hz 70% duty. I got 14.3Vdc on the output when i started my car.

Well when i turned PWM off DCDC was sitting there with Aux battery at 13.6Vdc. If i would turn ON the lights DCDC would cover the difference. It is kind of nice to not worry about Aux battery, but it would be good if i was able to shut it off completely.
I experiemented with commanding 30% duty and DCDC would actually shutoff when that pwm value would be applied. If i would turn pwm off DCDC would revert to 13.6Vdc.
I also tried to put pin 6 (5V pullup) to GND while unit was operating. This didnt do anything noticable.

My intent is to keep DCDC down by 30% duty at all times when car is off except when charging. There i will turn pwm off to power coolant pump and fans and heaters i eventually might build in.

[ggeter]

Yesterday i installed my Volt Gen2 DCDC in my Pug and i supplied it with 12Vaux battery and HV. I used 5V pwm signal from my DUE board and set it to 110Hz 70% duty. I got 14.3Vdc on the output when i started my car.

Well when i turned PWM off DCDC was sitting there with Aux battery at 13.6Vdc. If i would turn ON the lights DCDC would cover the difference. It is kind of nice to not worry about Aux battery, but it would be good if i was able to shut it off completely.
I experiemented with commanding 30% duty and DCDC would actually shutoff when that pwm value would be applied. If i would turn pwm off DCDC would revert to 13.6Vdc.

My intent is to keep DCDC down by 30% duty at all times when car is off except when charging. There i will turn pwm off to power coolant pump and fans and heaters i eventually might build in.

Thank you!

[arber333]

There was a question about annoying noise from Volt Gen1 DCDCconverter.

I think the thing likes being loaded. If you keep LV lines unloaded it will struggle with keeping the voltage level. Try giving it some H4 or H7 light bulbs to chew or larger 12V battery when testing. I bet it will stop whining. The same was true for Volt Gen2 DCDC as well.
In any case you need to have 12V battery connectedandapply some load to thecircuit.

[ggeter]

Searching for a compact watercooled DC-DC converter I came across the GM Volt Gen2 DC-DC converter.
Bought one at Ebay and just figured some things out:

Do we need to pre-charge this unit? Or can I just put a 400v/80a relay on the main supply and just flip it when I turn on everything else?

[EV_Builder]

There was a question about annoying noise from Volt Gen1 DCDCconverter.

Maybe lower or upper the voltage setpoint?
Its adjustable with a reason i would say

[arber333]

Do we need to pre-charge this unit? Or can I just put a 400v/80a relay on the main supply and just flip it when I turn on everything else?

I keep it connected to HV allways so i dont have a problem with precharge.
I would say there is very small jolt upon connecting DCDC HV connector and i havent seen any prechage mechanism in Volt gen2 for DCDC.
Why not use second key lock position to start precharge on your inverter and the "starter on" position to open contactors for inverter and DCDC and pumps and heaters etc...

The same would apply for gen2 charger. But I kept it connected to HV through 30A fuse allways.

[FJ3422]

Do we need to pre-charge this unit? Or can I just put a 400v/80a relay on the main supply and just flip it when I turn on everything else?

Did not check that (yet). But it's easy to check; look at the PCB and see if there is a current-limiting device between the HV-connector and the HV-capacitors.

[ggeter]

Do we need to pre-charge this unit? Or can I just put a 400v/80a relay on the main supply and just flip it when I turn on everything else?

Did not check that (yet). But it's easy to check; look at the PCB and see if there is a current-limiting device between the HV-connector and the HV-capacitors.

Do you see indication of any current-limiting functionality in these pics?

viewtopic.php?p=25287#p25287

[arber333]

There is no current limiting resistor there. How do i know? Because i burned one of them when i accidentaly reversed polarity .
There is plenty of film caps to absorb the spike at connection though.

[EV_Builder]

And I see 2 inductors which are if I'm right prime examples of current change limiters.

[arber333]

Lately i hear strange schratching noise from Gen2 DCDC when i go under the car. That is with the car off! I think it is complaining the load is not high enough... Maybe i will nave to implement 30% duty PWM signal from DUE control when car is off to keep DCDC truly off.

[ggeter]

Lately i hear strange schratching noise from Gen2 DCDC when i go under the car. That is with the car off! I think it is complaining the load is not high enough... Maybe i will nave to implement 30% duty PWM signal from DUE control when car is off to keep DCDC truly off.

It appears I can move forward with plan to put a relay in front of the unit and cut it on with everything else, no precharge required? I'm not interested in leaving it on all the time.

[ggeter]

Also, confirming the binder posts are M8 studs?

[arber333]

Also, confirming the binder posts are M8 studs?

Check.

[arber333]

I just revisited my DCDC PWM command effectiveness. I found out DCDC would come to 14.2V for 1/2s and then drop to 13.6V when the car would be on!!!??? This created a kind of flicker in car lights that wasnt noticable in daylight.
I had PWM set to 115Hz and 70% duty. I guess it is not enought Hz?
I changed that to 120Hz and 70% and i got a good steady power from DCDC.
Also since i was correcting the code i decided to turn off DCDC when car would be off. However when EVSE would be connected i need to have DCDC on standby since i need to ower pumps and fans for my chargers.
So now when car is off i command PWM 120Hz at 33% and DCDC would shutoff.
Also when EVSE is connected i turn off PWM and i get DCDC in standby at 13.6V.

Code: Select all

if (digitalRead(Enable_pin) == HIGH) { // if Enable_pin senses ignition 
  if(millis()-lastime > myVars.transmitime)  //Nominally set for 120ms - do stuff on 120 ms non-interrupt clock
    {   
     lastime=millis();        //Zero our timer
       sendCANframeE(); 
       printstatus(); 
       sendCANframeD();
       printstatus(); 
       }         
digitalWrite(DCDC_active,HIGH); // turn on DCDC_active relay
PWMsignalDCDC(); //signal DCDC ON
} 

else if (digitalRead(PP_relay) == HIGH) { // If charger is connected
digitalWrite(DCDC_active,LOW); // turn off DCDC_active relay   
pwm.stop( 6 ); //stop PWM on D6
 } 
 
else {
digitalWrite(DCDC_active,LOW); // turn off DCDC_active relay
PWMsignalDCDCoff(); //duty at 33% to shut down DCDC
 }     
 .........................................................................
 
 void PWMsignalDCDC()
{
pwm.setFreq1( 120 ); //setup frequency
pwm.pinFreq1( 6 );  // Pin set to "pwm_freq1" on clock A  
pwm.pinDuty( 6, 180 );  // duty cycle on Pin 
}

void PWMsignalDCDCoff()
{
pwm.setFreq1( 120 ); //setup frequency
pwm.pinFreq1( 6 );  // Pin set to "pwm_freq1" on clock A  
pwm.pinDuty( 6, 85 );  // duty cycle on Pin 
}

[Gregski]

just got my second gen Charger/Converter set on eBay, sharing the Converter listing (items were purchased separately) to show folks what they go for as of the current date, brace yourselves for death by a 1,000 questions, ha ha, I know nothing about these things, and I'm prepared to share all I know

Part Number: 24284603
Supersession(s): 24274770; 24280796; 24290992
https://www.gmpartsmog.com/p/70072595/24284603.html

unlike it's charger counter part, the converter sports a single orange unicorn

[Gregski]

this shows where Chevy Volt Gen 2 (2016-2019) DC-DC converter aka the Accessory Power Module or APM is housed inside the trunk of the vehicle in case you find one in the wild and want to lift it

[Mitchy]

Had time to scan this unit in 3D
Uploaded to GrabCAD:

https://grabcad.com/library/chevy-volt- ... c-module-1