400 amp service solar upgrade, existing micro inverters removed to be DC coupled only, then upgrading to Dual Gridboss Flexboss21 Stations

Interesting setup - going full DC coupled is a bold move but honestly makes a lot of sense if you're ditching the micros anyway. Less conversion losses and you get proper battery backup capability which microinverters never really gave you.

Curious what you're running for battery storage alongside the Flexboss21s? That's a serious amount of kit for a residential setup. Dual units suggests you're pulling some decent loads - EV charging by any chance? 😄 (asking for obvious reasons)

I went down the DC coupled route with my shepherd's hut install and the efficiency gains were immediately noticeable. Nothing on the scale you're talking about obviously, but the principle holds at any size.

A few things worth thinking about as you plan this out:

• Stringing - how are your panels currently configured for the micros? You'll likely need to reconfigure for MPPT input specs
• Protection/isolation - with 400A service you'll want to be absolutely sure your DC disconnect and breaker sizing is sorted before anything goes live
• Grid interaction settings - worth getting ahead of your DNO requirements early, they can be slow

What's the timeline looking like? And are you doing the install yourself or bringing in a sparky? That 400A service upgrade alone is a job and a half.

Would love to see some photos when it comes together - this sounds like a proper beast of a system.

@GazAllen what's the advantage of going with dual Flexboss21 stations over something like a pair of Victron Multis in a stacked setup? Genuinely curious as I've not seen the Flexboss21 get much attention on here.

Also — with DC coupling, are you planning to use separate MPPTs or does the Flexboss21 handle that natively? I'm looking at something similar for my garden office build and trying to figure out whether DC coupling actually simplifies the hardware count or just shifts the complexity elsewhere.

The conversion loss argument makes sense on paper but I've seen people underestimate how much cabling and fusing gets involved on the DC side when you're talking 400A service levels. What gauge runs are you planning?

@MelKing83 curious about this too — does the Flexboss21 handle parallel stacking natively or does it need additional comms hardware like Victron does with the VE.Bus?

Also wondering how the DC coupling side works when you're pulling serious current for EV charging. At my cabin I'm only dealing with modest loads but 400A service suggests someone's planning on shifting a lot of power. Does the Gridboss system have a proper load management protocol to prioritise solar > battery > grid for the EV side, or is that configured manually?

The Victron ecosystem handles this reasonably well with ESS but I've always found the setup fiddly. Keen to know if Gridboss has a cleaner interface for that kind of dynamic load balancing.

@OffGridFreak from what I've seen the parallel stacking on those units needs a comms cable between them, not just AC coupling — similar to how Victron handles it with the VE.Bus setup tbh

For emergency backup use (which is my main concern) DC coupled is definitely the cleaner approach. Fewer points of failure. My Victron Multiplus setup taught me that lesson the hard way when a micro inverter dropped out mid-storm and killed the whole chain

@GazAllen what battery chemistry are you pairing with this? Curious whether the Flexboss21 BMS comms plays nicely with LiFePO4 — Fogstar Drift cells or similar. That's usually where these less common inverter brands can get a bit sketchy compared to Victron's ecosystem

@TelScott75 raises a fair point about the comms cable, but I'd want to know more about how the Flexboss21 handles grid interaction at 400A service levels before getting excited about dual stacking.

Went through something similar on my narrowboat conversion — ditched AC-coupled micros, went full DC coupled with Victron kit, and the difference in battery charging efficiency alone was worth the faff. Less conversion stages means fewer points of failure too, which matters when you're living off the thing.

My skepticism here is around whether the Gridboss ecosystem has the same depth of monitoring and configuration that Victron's VRM platform gives you. That transparency is what saves you when something goes wrong at 2am. Anyone actually running Flexboss21 long-term with real load data rather than just spec sheets?