So I've been running a MultiPlus 12/3000/120 in my off-grid shed setup for about eight months now and kept getting random shutdowns whenever I fired up my table saw (roughly 1800W running, but the startup surge is probably double that). Turned out the DC cable run from my 200Ah lithium bank was just slightly too long and undersized — I'd used 35mm² but should have gone 70mm² for the 4.5 metre run. Voltage drop under surge was tripping the low voltage cutoff even though the battery itself was fine.
Swapped to 70mm² last weekend with proper crimped lugs and the difference was night and day. No dropouts at all now, even when the saw kicks in cold. Seems obvious in hindsight but I genuinely didn't think a few metres would matter that much at 12V. Lesson well and truly learned — 12V systems are absolutely brutal about cable sizing compared to 24V or 48V.
Has anyone else had similar issues with surge loads on a MultiPlus or another inverter/charger? Particularly curious whether anyone's moved to 24V or 48V specifically to get away from the cable sizing headaches on 12V. I'm half tempted to rebuild the whole bank at 48V when the budget allows — the wire savings alone seem worth it.