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izeman avatar image
izeman asked

Multiplus II GX - USB died AGAIN

Ordered a Multiplus II GX some weeks ago. Had a serial adapter connected to monitor the BMS of my battery. Had the serial adapter connect and reconnect all the time (while it was physically connected though). Then after two days it stopped working. Didn't accept ANY USB device.


Had the device RMA'd and the new one shows exactly the same issue. The USB port seemed to have died. Is the port that delicate? I have never seen such issues.


Any idea what to do? I don't want to send the device back again, but need a working USB. The USB is needed as the last resort in case the inverter is stuck so you can FACTORY RESET it with a USB stick. And I need to monitor my BMS as well.


Is there some internal USB port that can be used? Any ideas? Every idea much appreciated. I need to get this project and and running and close it...

Multiplus-II
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5 Answers
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sl1me answered ·

Are you using a galvanically isolated USB-Serial adapter? If not then there could be a ground loop or voltage differential thats killing the USB port. Below is what I use..

https://www.seeedstudio.com/USB-TO-RS232--RS485--TTL-Industrial-Isolated-Converter-p-3231.html




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izeman answered ·

No. I'm using a "regular" cheap USB/serial adapter from Amazon. But where should the voltage differential come from. There is only GND, TX, RX connected to the BMS.

And the serial adapter is connected via USB. I use it all the time and never had a single issue with any PCs.

The linked converter looks great, and I will probably get it, but what to do with the most likely broken USB port? I can't do any factory reset w/o being able to use an USB stick ...

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Meine_Energiewende avatar image
Meine_Energiewende answered ·

If it is one of these cheap BMS which shuts down you negativ path and you are using an non isolated usb <-> serial adapter it will fry your Board because of the ground loop over GND of the serial adapter which is connected to the BMS -> which has connection to battery minus.

All explained in victrons wiring unlimited. Victron states, that they will deny warrenty in this case.

Jens

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izeman answered ·

Seems like a proper cause for the failure. Well, and I checked that 70 page document (which btw is not included with the inverter), and it didn't find anything that hit I was not aware that shorting your TX or RX to GND will fry your USB port?my eye. Maybe you can show me the correct paragraph.

I'm not sure you can deny warranty that easily.

Anything I can do? Is there a spare USB controller on the board - now that it's fried anyway and most probably won't get replaced?

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izeman answered ·

Any idea how I could get battery BMS into venusOS in a different way? I thought of adding a MK3 interface between a Raspberry and the GX to make the Raspberry (with working USB) the control unit?!

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