3 x Multiplus-II 48/3000/35-32 - 6 x Pylontech US3000C - Batterie Speicher Erweitern?

Been thinking about this after seeing a similar setup discussed elsewhere — three-phase Multiplus-II config with a Pylontech stack, looking at expanding the battery side.

Got me wondering about my own situation. Running a single Multiplus-II 48/3000 in my static caravan with 4 x Pylontech US3000C at the moment. System's been rock solid for about 18 months. But I'm starting to eye up adding another 2 or 3 units to the stack, especially with winter coming and the solar harvest dropping off.

Few questions for anyone who's done a Pylontech expansion mid-system:

• Did you need to reconfigure anything in VictronConnect/VEConfigure once you added the extra units?
• Is there a max stack size Victron will actually "see" properly via the CAN bus, or does it just read whatever Pylontech reports?
• Anyone had issues with older and newer US3000C batches not playing nicely together? Mine are from Fogstar, wondering if a second batch from the same place would match okay.

The German forums have loads of detail on three-phase ESS setups but it doesn't always translate cleanly to what we're doing here — most of us are running single-phase, smaller sites, shepherd's huts, static vans, that sort of thing rather than full house ESS.

Curious what others are running. Anyone pushed a Pylontech stack beyond 6 units on a single Multiplus-II? Where does it start getting complicated?

Expanding a Pylontech stack mid-deployment is like adding carriages to a moving train — technically doable but you'll want matching firmware across all US3000C units or the BMS throws a wobbler and your Victron system starts sending you passive-aggressive alerts at 3am.

@KentCruiser love the train analogy 😄

Done exactly this with my cabin setup — added two US3000C units to an existing four-pack. Key thing Pylontech themselves say: new batteries need to be the same firmware version as the ones already in the stack, or you're asking for trouble with the BMS communication.

Worth pulling

Hey all, jumping in here as I went through this exact process last spring with my narrowboat setup.

One thing worth flagging that I haven't seen mentioned yet — when you're expanding a Pylontech stack mid-deployment, make sure the new units are on a very similar state of charge to your existing ones before you connect them up. I'd recommend charging the new batteries independently first (Pylontech do specify this in their docs).

Also worth checking your DVCC settings in VenusOS are configured correctly for the expanded capacity — mine needed a small tweak after I added units. The BMS master battery count parameter in particular.

@T6Wanderer what's your current VRM setup like? That'll help determine how straightforward the expansion will be for your specific config. 😊

@Donna1998 narrowboat is a really interesting use case — curious what your actual usable capacity looks like day-to-day after the expansion?

I'm at a similar crossroads with my tiny house build. Currently spec'ing out whether to start with 4 x US3000C or go straight to 6 from the off. The Pylontech BMS does the balancing across the stack automatically doesn't it, or do you need to do anything manually when adding new modules?

Also wondering whether the Multiplus-II 48/3000 would cope if I eventually want to add EV charging into the mix — seems like the 3000VA rating might become a bottleneck pretty quickly.