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xxn5ac asked

Adding additional 50A plug to MultiPlus II

I have a MultiPlus II 2x120 in my RV along with solar and 10.4kWh of LiFePO batteries. This system is incredibly flexible and provides a lot of benefits including the ability to operate for extended periods of time without hook-ups (shore power) and the ability to operate as if I had 50A service when I only have 30A.

I have added a PHEV to my vehicle line-up and would like the ability to share 50A service with the other electronics in my RV. I would like for the PHEV to have "priority" on the electric service if that makes sense -- it wants to draw 7.5kW when plugged in and I have a Level 2 charger with a 14-50R plug.

My thinking is that I will install a 14-50R receptacle in the RV that I can plug the Level 2 charger into. My question, though, is where to draw power from. One option would be to add a breaker and pull off of the same 50A service (shore power). If I do this, one issue I could have is drawing too much current from shore power unless the MultiPlus II knows about the Level 2 charger. I do have a current monitor but have never used it. Could I connect the current monitor on the main feed from shore power and then parallel the MultiPlus II and the 14-50R for the charger. Would the MultiPlus II restrict it's current knowing how much total current is being drawn and the limit in the MPII?

Another option would be to put the plug on the output of the MultiPlus II. I don't expect to be able to charge without any shore power (my PHEV has a 17.2kWh capacity and my RV only 10.4kWh so it makes no sense to let it draw down the battery if I'm not on shore power). My MPII is a 3kVA unit, but I believe this is just the rating for the inverter. If I was plugged into a 30A service (providing only 3kW of power), the MPII can only make up another 3kW so I'm shy of the current required to charge the PHEV, BUT my charger will allow me to lower it's current draw so I could set that at say 5kW and allow it to charge from both batteries and the shore power. This would allow me to quick-charge the vehicle (this would take about 3h at that rate), draining the batteries some during that time and then when I leave in the vehicle, the MPII would continue to charge the batteries in the RV from the 30A shore power.

Has anyone tried this? Any ideas on the best approach? I've attached a drawing of my current setup without the PHEV power connection for reference.


390RK Solar-11.drawio.pdf

Multiplus-IILithium Batterysplit phaseshorepower
390rk-solar-11drawio.pdf (6.5 MiB)
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1 Answer
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markus-001 answered ·

Could you not use the AC-Out-2 on your Multiplus ii just check the specs early models had a 35amp contactor later models 50 amp.

Check the data sheet notes 8

With assistants in the multi plus ii you could set the AC-Out-2 contactor up as you wish.

You could change RV loads to AC-Out-2 set up to stay connected when there is no shore but disconnects if total loads exceed 5000watt with an auto reconnect if loads drop below 500watt and that would disconnect and allow full priority to AC-Out-1 (PHEV) just leave lights on AC-Out-1 so you don’t land up in the dark when AC-Out-2 disconnects. You could also have a manual reconnect push button to pull in AC-Out-2 again. You could leave the contactor engaged and allow batteries to discharge to a SOC of your choice then disconnect.

You could also just put the PHEV on AC-Out-2 and bring that contactor in and out depending on AC loads, SOC etc, you can also set a delay in seconds to prevent nuisance disconnects.

On the 230 volt units I would add an ET112 energy meter on that Output set the Cerbo up to see that ET112 as an AC Load meter instead of a grid meter, that would now display the load separately to the PHEV in the Cerbo device list but sum both AC-Out-1 and AC-Out-2 on the main page.

The ET112 displays kwh totalizer, amps and volts in the meter so you would have an incrementing kwh meter then know exactly how much you have charged the PHEV through the RV you just need to find the right energy meter for your US version.

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