Victron 250/85 mppt solar charge controller wont comms with Cerbo GX-S

Q&A and troubleshooting
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1

My 250/85 is 8 years old, and has had a blue tooth smart dongle connected to it for years, on the Ve.Direct port.

Its firmware is up to date. However to run a BMS in conjunction with a newly installed Cerbo-S I needed to connect this

solar charge controller to the Ve.direct ports on the Cerbo, however, it is not detected by the Cerbo and the 250/85 is not responding

to external control despite being set to “smart Lithium” settings. Very strange that the 250/85 ve.direct would work with the victron bluetooth dongle but

wont talk to the Cerbo. Is there something I am missing?

2

When I plugged the original bluetooth dongle back in to the same 250/85 mppt, it does not work anymore. So the ve.direct port on the 250/85 I thought must be dead. When I test the individual pins on the ve.direct with a multimeter, pin 4 which is “+ power” it is reading 5 volts, although the voltage does wobble.

3

Did you use an original Victron VE.Direct cable ? If it is DIY you have to drop the “+ power” line or you will fry the communication board.