This coming week, I'll start installing my first significant off-grid PV + battery system. For a sweet little organic farm.

The plan is to install Victron equipment. Victron arguably makes the most robust and reliable PV electronics on Planet Earth. ...Rocking iron-core transformers like it's 2003. And they're super programmable (for the computer nerds out there). Local first.

Trying to design this Victron system... has been very humbling. I got my ass kicked. The system is so modular... lots of different components to integrate (correctly!).

For this farm system:

Pick the right Victron charge controller. The most practical option could mean as few as three modules per string. Combine the strings first (outside, at the PV array, in a rainproof box), with each one having over-current protection and disconnect (I'll use DC breakers). In the indoor-electronics room (in my case, a metal shed), the combined conductor also needs a DC breaker, in a box (i.e. a metal enclosure). Then into the charge controller. Another DC-breaker box between the charge controller and the battery bank.

I plan to use two 48v 100ah Discover rack batteries, which each have their own disconnects.

The farm's main load is a 5-horsepower 240-volt pump, with 26 amps normal operating current. For this, I'll use two Victron Quattro 10kva 120-volt inverters. I'll install a soft starter on the pump (I'll write a blog post about this).

So two inverters, paired for split-phase output. In a box between the battery bank and the inverters: Each battery — in parallel — will connect to a DC bus bar. On that bus bar, the two inverters will each have a 250-amp breaker.

I'll use MidNite boxes and DC breakers. Possibly a (smaller and less expensive) Outback box for the inverter breakers.

Also, a Victron device for communication and remote data access. And a separate Victron screen.

Awesome that the system is so modular. It's relatively easy to swap out failed components, and expand the system later. It all can fit in tighter spaces (like in a boat or tiny house). And I like that everything is so exposed and traceable (although I'm sure that many would prefer having the wires and other complexity hidden away in one big box). With appreciation, my friend Ari referred to this modular approach as the raw old-school nuts-and-bolts way.

...This is the only way with Victron equipment. And it's the way with MidNite Solar's 120-volt Rosie inverters (which, like Victron inverters, are war horses with transformers).

And then there's (transformerless) all-in-one inverters, which have more-or-less taken over. ...Probably have more modules per string, with fewer strings. Bring the strings directly into the inverter (that has integrated PV-string breakers). Just a positive T fuse and negative bus bar between the battery bank and inverter — the inverter has integrated battery-bank breaker(s). So much easier.

And the overall system cost can be a lot lower with all-in-one inverters. Especially if using equipment from EG4... weirdly low prices for what they offer. Victron equipment will last a lot longer, and Victron is more likely to stick around to honor their warranties. Paul from Zonna Energy said, on the other hand, that EG4 pricing is so good that you could buy an extra one to store as backup.

I think the best all-in-one inverter is MidNite's. For one thing, incredible surge capability. But I was a little bummed to hear that it's actually made by a different company, in Asia. The Rosie, on the other hand, is straight-up made by MidNite right here in the U.S.A. I heard a rumor that MidNite might offer an all-in-one split-phase inverter based on the Rosie architecture. ...That would be sweet.

Back to the farm. I'll start with the PV array, metal shed, and trenching to the pump. I need to get the farmers an updated cost estimate for the Victron + Discover + MidNite equipment. They want to play the long game, with equipment built to last. Hopefully the latest cost estimate will still work for them (my earlier (naiive) cost estimate was too low).

Any mistakes here are 100% mine. With that said: Thanks so much to the peeps that helped me better understand Victron system design: Kindle at Greentech Renewables, Paul at Zonna Energy, Ari at Alpenglow Off-Grid, and Midnite Solar.