EcoBob
New Member
My Solax x3 hybrid g4 15kw + 2 x 5.8kWh battery system is installed in an outbuilding, with supply current monitoring by CT in the house, next to the supply meter. The connection to the inverter is via 20m of (earthed screen) cat6a. We just had the supply meter changed to a UK smart meter so we can get paid for exports.
As far as the inverter is concerned, everything is hunky dory - it thinks it is supplying all the house needs from either PV or battery, and not importing anything, but.... The supply meter disagrees.
When there is insufficient PV input to export, and the batteries may be supplying / supplementing the output, the supply meter says I'm importing 60 to 100W, or around 2kWh per day, which is wiping out any export payments. When the battery is fully charged and the inverter is exporting, the supply meter stops racking up imports. This did not happen with the old meter - that reported about 0.1kWh or less imported per day so it wasn't worth worrying about. This is probably due to the new meter being more sensitive, rather than faulty.
When I compare the phase currents on the inverter and smart meter, there is a difference roughly corresponding to the 100W reported discrepancy.
I've tried changing the Pgrid bias parameter to "grid" and this does reduce the inverter consumption from about 0.5kWh to 0.2kWh / day, but the supply meter still reports 2kWh imports.
The CTs are 100A/33mA so with currents of around 1A in the phases, the feedback voltages in the inverter must be tiny. I'm wondering if I really ought to be monitoring the grid supply currents with a meter and sending RS485 to the inverter instead of using analogue CTs. Any thoughts?
As far as the inverter is concerned, everything is hunky dory - it thinks it is supplying all the house needs from either PV or battery, and not importing anything, but.... The supply meter disagrees.
When there is insufficient PV input to export, and the batteries may be supplying / supplementing the output, the supply meter says I'm importing 60 to 100W, or around 2kWh per day, which is wiping out any export payments. When the battery is fully charged and the inverter is exporting, the supply meter stops racking up imports. This did not happen with the old meter - that reported about 0.1kWh or less imported per day so it wasn't worth worrying about. This is probably due to the new meter being more sensitive, rather than faulty.
When I compare the phase currents on the inverter and smart meter, there is a difference roughly corresponding to the 100W reported discrepancy.
I've tried changing the Pgrid bias parameter to "grid" and this does reduce the inverter consumption from about 0.5kWh to 0.2kWh / day, but the supply meter still reports 2kWh imports.
The CTs are 100A/33mA so with currents of around 1A in the phases, the feedback voltages in the inverter must be tiny. I'm wondering if I really ought to be monitoring the grid supply currents with a meter and sending RS485 to the inverter instead of using analogue CTs. Any thoughts?