I added this geyser control to my Victron dashboard app. It controls a relay on the Venus GX. Once we out of lockdown I'll wire it up to a power relay on the geyser.

Edited April 14, 20206 yr by deapsquatter

On 2020/04/13 at 10:45 PM, JaseZA said:

I have an Axpert VMiii - doesn't give me any info on available power unfortunately. Will keep testing my PV voltage program and see how it goes...

An idea i had in the dead of night is to perhaps use a separate PV panel for sun intensity measurement. (It can be a small one)

This will provide an indication of sun power available that won't fluctuate depending on the load on the inverter. Less headaches on how to do the control!

Used a Arduino with a light sensor to control the switching of water pump . Cant that be used to determine the amount of light  available .

A point about getting maximum power out of a PV system was made by someone on another forum:

If this was a grid-tie system the solar would always produce maximum power. Some would go to the demand load and what is left over would be fed back into the grid. Weather this is wasted or saves you depends on your meter and the local laws.

9 hours ago, Richard Mackay said:

An idea i had in the dead of night is to perhaps use a separate PV panel for sun intensity measurement. (It can be a small one)

This will provide an indication of sun power available that won't fluctuate depending on the load on the inverter. Less headaches on how to do the control!

I have also thought of something very similar: You have a small solar panel, say 5 to 10watts. Connect it to a resistor to match its maximum power point. The power % produced will be in proportional to what your solar PV can output. Then take that voltage from the panel, scale it through a resistor network, and use that voltage on a raspberry pi or arduino or whatever microcontroller. I haven't tried it (yet). What do you guys think? Maybe have a solar panel much smaller like  a 1 watt if that is available to reduce the size of the resistor. The reason for the resistor is to get wattage out of the panel as I think that the voltage could not be an accurate measurement of actually available pv power (could be wrong).