Anyone else running a Victron MultiPlus in a shepherd's hut? Sizing questions inside

Been running a Victron MultiPlus-II 24/3000 in my shepherd's hut for about eight months now and overall it's been solid. Paired it with a Fogstar 24V 200Ah lithium and roughly 600W of panels on the roof. Handles the basics fine — lighting, laptop, small fridge, phone charging.

Problem is I want to add a small induction hob (around 1800W rated) for occasional cooking. The MultiPlus should technically cope in theory but I'm seeing some weird behaviour — it cuts out briefly when the hob ramps up, then recovers. Not throwing any alarms, just a momentary blip. Wondering if it's the PowerAssist kicking in oddly or something with my DC wiring.

Anyone dealt with similar on a 24V system? Wondering if I've just got undersized DC cables between the battery and inverter causing a voltage sag at the moment of inrush. Cables are only about 1.5 metres but I went with 35mm² which I thought was plenty.

Also curious what others in similar small off-grid buildings are running — is a 3000VA unit the sweet spot or should I have gone bigger from the off?

JennyWilson | 47 posts

@BigAl27 nice setup! I've got a MultiPlus-II 48/3000 in my shepherd's hut and honestly it's been brilliant. One thing worth checking - have you set up the ESS assistant or are you running it purely off-grid? Makes a big difference to how the system behaves.

On sizing, 600W of panels into a 24V 200Ah battery is workable but you'll feel it during a run of grey days in winter. I topped mine up to 900W and it made a noticeable difference through December and January.

Also make sure your VE.Connect profiles are dialled in properly for the Fogstar - lithium settings straight out of the box aren't always optimal. What charge voltage are you running it at currently?

PeakCruiser | 203 posts

Nice one @BigAl27, that's a tidy little system! Eight months is long enough to really know where the pinch points are.

One thing worth checking if you haven't already — have you dialled in your charge current limits properly in VictronConnect to match what the Fogstar BMS will actually accept? I've seen a few people catch the MultiPlus pushing slightly more than the battery wants during bulk, especially on a bright spring morning when the panels are firing and shore power kicks in simultaneously.

Also, what's your load profile like? 24/3000 gives you a solid 2400W continuous which should be plenty for a shepherd's hut, but if you're running anything with a chunky startup draw — a small immersion or air source heat pump — it's worth checking the assist settings.

What firmware are you on currently?

SilverMender | 203 posts

Great thread @BigAl27! One thing worth mentioning that I don't see discussed enough with the MultiPlus-II in small spaces like shepherd's huts — have a look at your AC input current limit settings if you're ever connecting to shore power. The 24/3000 can draw a fair whack when bulk charging and simultaneously powering loads, so dialling that back in VictronConnect can prevent tripping a weak supply.

Also, with 600W of panels on a 24V system, make sure your MPPT is properly sized for any future expansion. It's surprisingly easy to outgrow your charge controller before your batteries. What MPPT are you running alongside it? The SmartSolar 100/30 would be cutting it close if you're thinking of adding panels come winter when you'll really want every watt you can get.

RussGreen | 89 posts

Coming at this from a van conversion background so slightly different use case, but I ran a MultiPlus-II 24/3000 for about 18 months before upgrading. One thing that caught me out early on — the AC input current limit setting in VEConfig. Default's often set too conservatively and if you're shore powering the hut occasionally it'll throttle your charge current more than necessary.

Also worth checking your DC cable sizing between the Fogstar and the MultiPlus. 24V systems pull serious amps under load and undersized cable causes voltage drop that can trigger low-voltage warnings even with a healthy battery.

@BigAl27 what's your charge controller? If it's MPPT, are you using the VE.Direct cable to link it into the Victron ecosystem? Makes a big difference having everything visible in VRM.

Interesting thread — I've got similar sizing questions but for a static caravan rather than a shepherd's hut. Does the MultiPlus-II handle well when you've got multiple loads switching on at the same time?

My worry is the surge when a fridge compressor kicks in at the same moment as something else fires up. Is the 24/3000 comfortably handling that in practice, or have you had any nuisance trips?

Also curious whether anyone knows if the MultiPlus-II works cleanly with Fogstar's 24V lithium range out of the box via VE.Bus, or does it need quite a bit of manual configuration in VictronConnect first? I'm still at the planning stage and trying to decide between that combo or going with a Renogy all-in-one setup instead.

Ella1966 | 341 posts

Great setup @BigAl27! I've got a very similar arrangement in my shepherd's hut — MultiPlus-II 48V/3000 rather than 24V, but the principles are the same. One thing I'd flag that nobody's mentioned yet: have a proper think about your transfer switch settings if you're occasionally plugging into a generator or hook-up. The MultiPlus can be quite fussy about accepting certain generator waveforms, and tweaking the AC input current limit in VEConfigure made a noticeable difference for me. Also worth enabling the "weak AC" setting if you're running a smaller genny. Eight months in you're probably past the teething stages, but those settings caught me out initially. What are you using for monitoring — the Cerbo GX or just the basic Color Control?