Additional solar array and battery


New Member
Jun 4, 2022
Broadstairs, Kent, UK
We already have an existing 4kw solar array, which was installed in late 2015, and we get reasonable FITS payments on this system, so can't alter it. We currently use about half of the 4000 odd kWh we generate a year, the rest just gets exported. So the plan is to add a battery, but that will really need more panels to be able to charge the battery fully during the better months.

The above system occupies the best roof's on the house, which leaves a NW facing roof with chimney that will cause shading, or we have a large 6 x 6 meter flat roofed garage, although it does suffer some shading early, and late in the day. I've been advised this would be the better option, with the panels arranged in an almost east - west arrangement.

Quotes I've been getting are just too expensive, so I'd like to DIY as much as I can, so been busy trying to learn.

We were going with another Solaredge system with power optimisers, but this adds up rather expensive and apparently the inverters are in short supply anyway.

I'm also considering a Victron inverter charger, and charging the batteries completely from the the excess AC power from the two arrays. I've been gradually watching all of Andy's Off Grid Garage videos (there's a lot of them) and learning from them. The thought occurred to me that we could use 4 MPPT chargers, and therefore four strings consisting of 3 panels each. We'd be using 405w panels, and I believe the MPPT 150/35 would be sufficient for the strings. Would this arrangement work almost as well as optimisers, I realise a lot depends on the shading?

Ideally I'd like whole house backup, or as a minimum critical loads, and I would build a 16S 48v battery, Victron have a wide range of inverter chargers, which type would be better for grid tied, and to use the existing and new solar array to charge the batteries?

I have so many other questions, as its a lot to get my head around, and take it all in, but I'll leave it there for the moment.