Growatt inverter monitoring with Raspberry Pi
At home we have a small (2.5KW - 10*250w panels) PV system to try and offset our daytime electricity usage. This is connected to a 'Growatt' inverter that handily has both RS485 (wierd 2 pin plugs) and RS232 (9 pin D connector buried under a screwplate) outputs.
With the firmware on ours (installed Sept 2013) it supports modbus-rtu over serial 9600 8N1.
I had done some initial digging and experimentation (as announced on Whirlpool) but never really got sensible values out.When my guruplug (via a long USB to serial adaptor) finally died and I shelved the whole thing. With the completion of the structured wiring though I finally got round to reconnecting it and starting again.
|Blue serial cable attached to structured wiring.|
Anyway, in the intervening time, someone had worked on my hacky scripts and wrapped the posting to PVoutput in an exec(curl) call -- first up I ripped that out and swapped for python requests.
I then went through the growatt modbus guide and made sure that it correctly calculated high and low byte values where these are split. The resulting script can be found on github, and todays output can be seen on pvoutput. - a couple of charts are duplicated below.
|Todays output v insolation prediction|