question

Some of the smaller Phoenix inverters do come in 120 volt versions. These talk to GX devices via VE.Direct and are not normally shown on the overview pages. However my GuiMods enhancement does add support for them.

https://github.com/kwindrem/GuiMods

I'd like to see a drawing of your "dual bus" system to better understand why a Multi wouldn't work in this situation.

True, having separate charger and inverter separates the two into separate boxes but don't see how that adds redundancy. If either component goes down, your system still isn't able to provide power to your loads.

The other thing with separate charger and inverter is there is no pass-through path so both the charger and inverter run all the time. This does isolate the output AC voltage and frequency from the incoming AC so that can be seen as an advantage if your loads require very stable power.

with a Multi plus - you would connect this DIRECTLY to the battery and the cerbo would then control the multiplus telling it to stop charging or to stop inverting so relays are not needed for the multi - and thats the same for the smartsolar mppt as well. this is applicable only if your batteries BMS is compatible with the cerbo and it does DCL DVL CCL control. you still need the relays to turn off other boat loads and or charging systems.

you could also look at buying a 220v kettle and toaster etc if thats all you are running on the boat AC wise. and then a phoenix would be fine.

Victron systems with Lithium batteries often have charge and load disconnects to protect the batteries. In these systems, the Multi connects directly to the battery and the BMS controls charging and inverting to protect the battery.

One advantage to a separate charger and inverter is the charger would typically run off of any shore power connection: 120, 230, 50 or 60 Hz, and the interior would always output a consistent voltage for your loads. With something like the Multi, you would need a transformer to accommodate various shore power voltages and your loads would need to work on 50 AND 60 Hz.

There are Phoenix inverters (no charger) up to 5000 VA. These higher VA rated units would connect via VE.Bus rather than VE.Direct. These would work with a GX device without my GuiMods.

None of the Victron chargers would interface with a GX device however.

Hi guys

So if I am reading this right - the multiplus would take the place of the HVC and the LVC relays? I know I can control charging with the cerbo GX, but thought I'd still need the relays as last ditch protection in case something went wrong.

Wouldn't that mean the unit would have to be on all the time? My plan was to shut down the unit when I wasn't using the inverter or the charger (which would be 95% of the time) in order to save power, and to avoid accidentally leaving the unit on.

You still may need protection from overcharging if other charging sources aren't of the three stage type (bulk, absorption, float). Another concern with multiple charging sources is exceeding the battery's maximum charging current. Victron inverter/chargers and the solar MPPT controllers can be throttled back using DVCC in the GX device but other charging sources may result in exceeding max charging current.

Protection from low SOC/battery voltage may also be needed depending on your loads. The Multi will cut off but other sources may not. Victron's battery protect devices integrate with a BMS via "charge disable" or "load disable" control lines. These would do the same thing as your relays. If your BMS doesn't communicate with VE.Bus, then you may need to route these same control lines to the Multi. I think the GX device can forward this information from CANbus, USB or other BMS that connect to the GX device but don't quote me. That would also mean the GX device would need to be on all the time which is a slight power draw from the DC bus.

You can turn the Multi on/off/charger only from the GX device. Power consumption is minimal of off or charger only.

Ok I think I get it. I can connect the multiplus up to my charge bus, it'd just stop the battery being protected from the inverter overdischarging it since it'd be on the wrong bus, with no way around that.