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dan-broad avatar image
dan-broad asked

Cerbo restarts when main dc supply is connected to Multiplus.

Hello,

I have tested my setup at home for a while and never saw this issue. Now the setup is installed in my boat, I’m getting the following.

The Cerbo will immediately shut down ( as if the power removed ) when the isolator supplying DC power to my MultiPlus 3k is switched to ‘ON’. This issue will only happen when the Multi has been without DC power for a few hours.


I have noticed there’s a substantial inrush current, where the Multi’s capacitors charge, could this have some connection to the issue?

The system setup is identical to when installed at home for testing; however the VEbus RJ45 cable between the Cerbo and the Multi is now 4x longer.

Any suggestions would be greatly appreciated.

Dan


Venus GX - VGX
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seb71 avatar image seb71 commented · 
The system setup is identical to when installed at home for testing; however the VEbus RJ45 cable between the Cerbo and the Multi is now 4x longer.

Does it still happens if you disconnect the RJ45 from Cerbo cable before connecting the inverter to the battery?


12V battery? If yes, maybe the battery voltage drops under 8V (minimum voltage listed for Cerbo GX power) when the inverter capacitors are charging.


Either way, you should precharge the inverter capacitors before connecting the inverter to the battery.

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Kevin Windrem avatar image
Kevin Windrem answered ·

I had this problem when I first powered up my system. The inrush from the Multi was causing the BMS in my Battle Born batteries to shutdown.

I added a manual precharge (switch and resistor) and the problem went away.

Battle Born makes an automatic precharge unit. They said I shouldn't need one on my system (Multi Compact 12 volt) and two Battle Born GC2 batteries in parallel). May be my battery cables were too big or too short.

There are other automatic precharge units on the market.

Originally, I thought I'd be turning off the inverter's DC power on a regular basis, but the current draw when the Multi is off is unmeasurable. I only turn off the inverter DC for maintenance.

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