Had exactly this with my garden office setup last winter. Old chest freezer compressors have a brutal inrush current — we're talking 3–6x the running draw for that fraction of a second when the thermostat kicks in. Your Multiplus absolutely hates that.
The thing that sorted mine was fitting a soft starter — I went with a Schneider Altivar, though there are cheaper options floating about. Dropped the startup spike dramatically and the Multiplus stopped throwing a wobble.
A few things worth checking first though:
- What's your battery bank doing during startup? If voltage is sagging hard, that's often the real culprit rather than the inverter itself
- Which Multiplus model? The 2000VA will struggle more than the 3000VA with old compressors
- How old is the freezer? Honestly, sometimes the compressor capacitor is just dying, which makes inrush even nastier than it should be
My bank is Fogstar Drift LiFePO4 cells and even with decent C-rate capability, the BMS was briefly disconnecting before I sorted the soft starter side of things. Victron's transfer switch settings in VEConfigure can also help — there's an UPS function toggle that changes how aggressively it responds to transients.
Worth posting your Victron Connect logs if you can grab them — the event history usually tells you whether it's an overload trip or a low voltage shutdown, which points you in completely different directions.
Anyone else found specific freezer brands worse than others for this? Curious whether it's just the really old ones or if newer budget chest freezers are just as bad.