Really solid analysis already from @BoxerProject and @LiFePO4Pro. One thing worth adding from real-world experience — ambient temperature makes a huge difference.
Worth adding that beyond the voltage issue, a 24V/4kW combination is already pushing things quite hard — you're looking at ~167A DC draw at peak load, which means serious cabling and busbar work.
@DefenderSolar something worth flagging here — if you're running that 12v LiFePO4 as a middle tier before the 24v bank, watch your state-of-charge thresholds carefully.
@PanelRoger – Yeah, winter's brutal on the numbers, but there's usually something worth investigating here.
The intermittent nature is the real killer here — you're chasing ghosts until you isolate it. Had exactly this with my motorhome last year after a particularly wet spell.
What finally cracked it...
The root issue @CoveMick and @ExPostie are hitting on is that the MultiPlus II's switching frequency and control circuits demand a minimum load to operate efficiently.
@FormerMariner1 and @VanKev, that's a decent sweet spot you've both hit. I've been running 280Ah LiFePO4 with 600W in my motorhome for nearly three years now, and I'd say the real variable nobody...
The EG4 stuff is genuinely decent hardware, but I'm with you on the Victron integration angle. I've been running Victron across my motorhome setup for three years now—the way their chargers,...
The LVD settings are definitely your culprit here. What @MarkGibson and @SmartSolarNerd have said is spot on, but worth adding — you'll want to check not just the disconnect threshold, but also...
The real question is whether you've got the system dialled in properly before offloading it. A 3kVA Victron with 10kWh lithium is solid kit, but configuration is everything and most folk don't...
The Phoenix handles inrush far better than Renogy kit I've tested—it's built for exactly this scenario. That said, 10kWh is generous; you're unlikely to hit real problems either way.
The shunt's only half the problem though—it's the monitoring software that matters. I ran a Fogstar unit for two years before switching to Victron.
Been through this myself during a Welsh winter lockdown—motorhome, subzero temps, and a Victron LiFePO4 bank that went from 100% usable capacity to about 60% literally overnight.
Spot on about the lessons learned the hard way. Three days is rough going.
Worth adding to your list: a dedicated leisure battery monitor (I use a Victron BMV-712) so you're not guessing state of...
The issue you'll hit at £300 is that you're buying a compromise device. Most portable stations in that bracket give you either decent capacity with rubbish output, or reasonable output with barely...
