openculture home solar

DIY residential off-grid setup · 48 V with grid backup

Project Anor

Two Victron inverters on one shared battery. A Multi RS Solar runs the light loads from its own panels. A MultiPlus-II runs the heavy loads, fed by two separate solar charge controllers. Grid is the backup for both.

0
Solar
0
Battery
6 + 10 kVA
Two inverters
48 V
System voltage, 16S

Wiring schematic

Solar DC Battery DC Grid AC Home AC CAN, RJ45 MK3 to VE.Bus, RJ45
Select any block for its specs and wiring. Combiner boxes open to show the wiring inside. Hover a block to trace its connections.

The equipment room: a Victron Multi RS Solar and MultiPlus-II on a steel rack, two SmartSolar chargers above them, breaker and distribution boxes below, and four battery packs stacked on the floor to the left

The install

A DIY install, planned, built and wired by bigbrovar. The Multi RS Solar and MultiPlus-II share a steel rack with the two SmartSolar chargers above them and the breaker and distribution boxes below. The four battery packs stand stacked on the floor beside the rack.

    The layout at a glance

    Two AC islands

    Light loads sit on the Multi RS. Air conditioners, the borehole pump, cooking and water heating sit on the MultiPlus-II. Each side has its own breaker, surge protector and RCBO board.

    Two ways in for solar

    13 panels go straight into the Multi RS’s two built-in trackers at high voltage. The other 18 go through two SmartSolar chargers, one 250 V and one 150 V, straight into the batteries.

    One shared battery bank

    Four 14.7 kWh packs are joined on one set of copper bars, called a busbar. Every charger and inverter connects to those bars through its own DC breaker. A SmartShunt and a small home-built monitoring computer (the GX) keep track of the whole bank.

    Sizing checks

    Do the strings and breakers suit the equipment they feed? Each check is worked out live from the datasheet numbers in the parts list, so it updates whenever the data does.

    10 °C

    Panels make more voltage in the cold, so voltage limits are checked at the coldest cell temperature you expect.

    Battery side

      How these are worked out
      • Cold voltage: Voc × panels in series × (1 + |temp. coeff.| × (25 °C − coldest °C)), compared with the charger’s absolute maximum PV voltage. The temperature coefficient comes from each panel’s datasheet.
      • Short-circuit current: Isc × strings in parallel, compared with the charger’s maximum PV short-circuit current.
      • Working current and panel power: compared with what the charger or tracker accepts. Going over isn’t unsafe; the charger trims the excess, which is called clipping.
      • String fuses and breakers: IEC 62548 puts their rating between 1.5 × Isc and 2.4 × Isc of one panel, and no higher than the panel’s maximum series fuse rating.
      • Surge protectors: their rated DC voltage should stay above the string’s cold open-circuit voltage.
      • Battery side: charger breakers at 1.25 × the charge current; inverter draw at a near-empty 48 V and about 94% efficiency; current shared evenly across the packs.

      A sanity check for readers, not a substitute for a qualified installer or Victron’s own sizing tools.

      Parts

      Tap a card to find it on the schematic