Been wrestling with this one for a while on the boat, so thought I'd throw it open here.
Running a Multiplus 24/3000/70 and during sunny spells the solar is absolutely hammering it — batteries topped off by mid-morning and the Cerbo's just sitting there watching excess generation go nowhere useful. Classic problem, I know.
My thinking was to chuck a triac-based power diverter (similar to what the iBoost or Marlec Solar iBoost+ does for grid-tied folk) on the 2kW immersion in the calorifier, basically bleeding off that surplus into hot water rather than curtailing it. Seemed elegant. Free heat, sorted.
Except — and here's where I'd love some input — I'm not convinced the Multiplus plays nicely with leading-edge phase cutting. The modified or chopped waveform that these diverters create can apparently cause grief with some inverter/charger combos. Victron's pure sine output is lovely, but feeding a reactive load like a phase-cut immersion back through the system feels like it could get ugly.
Has anyone actually run a power diverter off a Multiplus, particularly on a 24V system? I've seen some chatter about using the Victron MPPT + ESS assistant to manage this more cleanly, but that feels like overkill for a boat setup that isn't grid-tied anyway.
Alternatively — is a simple relay-switched immersion on a SOC threshold via Node-RED on the Cerbo the more sensible path? Less elegant but probably far kinder to the inverter.
Curious what others have landed on. There must be a few of you running surplus solar into thermal storage without frying anything.