Dual phase Solar install with Battery - Getting batteries to cross phases.

[catdog1121]

Ok so I am an electrician but don't really do solar, my partners sister has a holiday let complex, due to her energy bills rising to £36k a year they are going to get a solar and battery storage system installed...

They generally close over the winter so the load during the winter will be just their cottage.. The supply is a 2 phase supply, with a number of cottages on each phase. The solar and battery arrays they have been quoted for effectively create a solar array and battery on each phase.. The problem I have with this install is during the winter as their house is only on one phase it means half of the array will not be used.

running a new cable to their cottage to put some circuits on one phase and some on another would be expensive and difficult... I was thinking as the batteries will be next to each other is there any way of having it so one battery can charge the other battery automatically, so say when one battery is below 10% the other battery via DC cables uses its charge to charge the other battery? That way you keep the phases separate. Does anyone know if this is a thing or any other solutions that might work?

 

[snowhead]

You'd need to speak to whoever is quoting as it may need a different battery controller or it maybe that the ones they are going to use would do it and just need configuring.

 

[catdog1121]

You'd need to speak to whoever is quoting as it may need a different battery controller or it maybe that the ones they are going to use would do it and just need configuring.

The company that have quoted have just said to have two separate arrays so basically in the winter they will only be able to use half of the array.. I wonder if there is a way of isolating both batteries then switching the batteries between the phases and then powering back on, I guess this could be done with a switch or some kind of contactor that could then be controlled remotely but it would have to be manual rather than automatic..

 

[brianmoooore]

You should be able to parallel the outputs of the two inverters to combine them with suitable manual switchgear, but you need to consider the current flowing in any common neutral conductor. This will now be the sum of the currents from each phase instead of the difference.