HELP! Chevy volt APM module (DCDC converter)

[Boxster EV]

Hi,

I decided to fuse the + HV line running to my DCDC. I'm using Bussmann 15amp 500v fuse. Like this:



Now, when apply HV, and before applying low voltage signals to wake the DCDC up , I'm blowing fuses for some reason.

Could the DCDC be faulty or the fuse rating too low? Apparently the unit will only draw up to 10amps so it seems like there's a fault.

Any suggestions for testing? I'm reluctant to just give it the full 360v without fuse just in case.

[Isaac96]

It probably has capacitors which need to charge up, and the surge current is blowing the fuse. I'm running the same Volt module but it's installed after the contactors so that it precharges when the inverter does. The 12v signal to it comes from the main contactor coil.

So maybe try it with your contactor and precharge system and see how it behaves.

[arber333]

Hi,
Any suggestions for testing? I'm reluctant to just give it the full 360v without fuse just in case.

Use one 20A household auto fuse for testing first.
I connected DCDC directly to HV whithout contactor. I use 20A fuse from Ampera. When i connect through small connector i see a spark when DCDC is connected. So i keep it connected allways.
In Ampera there is a 10A relay inline and it opens when car is starting AFTER main contactor and inverter perform precharge. You may be seeing some spikes online from main contactor and inverter.

Anyway you start DCDC when you connect 12V enable signal to LV connector. Then you need to feed it CAN bus for a second or so to rise it to 14Vdc. Afterwards if you continue feeding CAN signal it will hold 14V, but really if you remove CAN signal and keep 12V enable connected it will hold 13.2V as long as it has 12V or enough HV.

[Kevin Sharpe]

Any suggestions for testing?

Use a kettle/oven heater element as the current limit for initial tests. You can also use the same element for manually precharging capacitors in the DCDC converter. I'm sure one of Damien's videos will show you how

[Boxster EV]

Thanks for the responses, folks.

I had the DCDC working fine several weeks ago when I last worked on the car. It was connected directly to the HV with no precharge. However it's after adding the fuse I'm now getting issues. I've tried it through the precharge after the contactors and it still does the same.

It must be related to a voltage spike. I've ordered some more fuses at 20amp to see what it does.

[arber333]

Just take one 16a auto fuse for household use and try if it holds. Use B rating first maybe C.

[Boxster EV]

Just take one 16a auto fuse for household use and try if it holds. Use B rating first maybe C.

I’m not sure what you mean by ‘auto fuse for household’. Do you have a link?

[arber333]

I’m not sure what you mean by ‘auto fuse for household’. Do you have a link?

https://www.tme.eu/en/details/cls6-b16/ ... -electric/

You can get that cheap in any hardware store. It works and i tested it on 25A 400Vdc load and it tripped and broke current repeatedly.
I meant that you can use it to figure out what is going on. And it is resetable...

[Boxster EV]

I’m not sure what you mean by ‘auto fuse for household’. Do you have a link?

https://www.tme.eu/en/details/cls6-b16/ ... -electric/

You can get that cheap in any hardware store. It works and i tested it on 25A 400Vdc load and it tripped and broke current repeatedly.
I meant that you can use it to figure out what is going on. And it is resetable...

Yes a circuit breaker. I’ll test this week and report back

[Boxster EV]

Just for completness and to conclude this thread, I wired the DCDC before the contactors and used a 16amp breaker as suggested above. It now works fine and draws about 8amps of current when LV is applied.