200+ Volts on SmartShunt

[drbytes]

Hello

So I've got a bit o an issue; my smartshunt reads over 200+ volts when there is a usb-to-serial connected. When it isn't connected the readings are fine.
This setup has worked for well over a year but then from one day to another it no longer read the right values.

It's hooked up to a pi that does the whole solar thing. I already tried interrupting the positive and groun wire from the usbtoserial to the smartshunt but the problem persists. The second I disconnect it it's back to normal.

Is it borked ?

 

[SeaGal]

Are you using the official Victron serial to USB lead, which is opto-isolated? Galvanic isolation will be required as the -ve battery terminal of some inverters (my Solis included) run at about -195V to PE. Connecting a device that is earthed directly to a smart-shunt's serial port doesn't do the smart-shunt any good... don't ask me how I know

My postings here may be of interest, although not directly related to the smart-shunt.

isolation of battery to inverter comms

I'm trying to get my head around how I've managed to blow a CANBus adapter (and fuse). Does anyone have experience of surge voltages may present on a battery to inverter CANBus link, when a battery is re-connected? In my case, I have a Solis hybrid (AIO) inverter, connected to my 14.3kWh...

diysolarforum.com

isolation of battery to inverter comms

Pretty wild having a 48V battery biased to some -150 or -200V with respect to earth. Is it floating, just charged up? Would a high impedance pull it back to relatively safe voltages? Yes, it surprised me to see that voltage on the battery, as I often touch my battery bus bars when it's all...

diysolarforum.com

 

[marionw]

You only need the two center wires (RX and TX) from the shunts VE.Direct port (it's an RS232-TTL port), you don't need pins 1 or 4 which are ground and +3.5vdc.
In addition is your PI powered via a DC-DC converter from the batteries? It is possible the cable from the shunt to the PI is creating a ground loop as both are sharing the same power supply.

 

[SeaGal]

You only need the two center wires (RX and TX) from the shunts VE.Direct port (it's an RS232-TTL port), you don't need pins 1 or 4 which are ground and +3.5vdc.

Should be 3.3V. Somewhere there will need to be a 0V reference for the TTL pins to work. Recommend galvanic isolation of the official cable - or make up your own opto-isolated circuit - e.g. like this one..

Victron VE.Direct – Alex' make and repair blog