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alan-offgrid-van avatar image
alan-offgrid-van asked

Inverter on house mains

Hi all.

I have a 400ah battery bank with a 3kw inverter that I use in my off grid caravan.

I was looking at a cost effective way to re purpose the above and hook it into my house to take advantage of the Octopus night tariff, that is a quarter of the day rate.

I was wondering if I could use the VE transfer switch so if the inverter is switched on it will use power from the inverter, and then switch back to mains when depleted.

I could then use a timer to charge the battery at optimal tariff time.

Does anyone have any advice or other ideas?

Much appreciated.

transfer switch
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3 Answers
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matt1309 answered ·

If the inverter is a multiplus ii then the setup I described will definitely work using ac in for grid/shore power. I'm not as familiar with other inverters so can't comment.


You can do it manually rather than rely on node red but node red is an easy way to change settings based on time.


For charging, schuduled charging is what you're after. However for timed discharging I believe node red is your easiest solution.

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matt1309 answered ·

Hi @alan-offgrid-van,

Do you mind explaining how your system is connected to the caravan?

If it's always connected to the grid/house one option could be to utilise node red to adjust the grid setpoint to a negative number at a specified time (ie discharge batteries and export to grid).

I've seen other people on this forum take it a step further and use node red or external server to get the energy prices from octopus energy via API to read the live rates (if you're on the tarrif where the rates are constantly changing per hour) and if the rates are particularly high that's when node red turns on the exporting (ie setting grid setpoint to a negative number)


For charging, there's the schedule charging feature built into venus os/cerbo gx however the node red approach will also work (ie setting grid set point to positive number to charge batteries)


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alan-offgrid-van answered ·

Thanks for your reply. I havent had a look at node red, so will need to do a bit more research.

My off grid solution is 430w solar onto 100/30 mttp to 400ah lithium, then 3kw inverter into the caravan hookup. Works well.

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