Panel/MPPT Size Question

[Axe21]

I was hoping I could get some advice on an upgrade to my current system. Currently I have a factory installed 320w panel on my 50amp RV. I was planning on going to the 48v EG4 6000XP but due to will latest video I don’t think that will be my best option. What I’ve decided to do is go with a Victron MultiPlus-II 2x 120V (with a 400ah battery) due to its 50amp capability. Here’s where I need some advice. I have one set of wires running from the roof down to my current MPPT and it would be very hard to get another set down to the storage bay. In addition, due to AC units, vents etc. and still have room to access the roof I don’t have a ton of room to add additional panels. Knowing I have one set of wire and limited room for panels what would you suggest Victron MPPT I use and what panels in order to charge the 12v 400ah battery.

Please let me know if you can help.

 

[sunshine_eggo]

You size the MPPT based on array voltage and output current of the MPPT.

A MPPT 100/50 is a very popular and cost effective controller - kinda their mid-range workhorse.

50 * 14.5V = 725W

Do you fully understand how the 2x120 unit works? It is only a 120V inverter. The only thing it can do with L2 is pass it through to the second panel leg when on 50A shore. It can't charge from it, or boost it or anything.

When inverting, it's like you're on single phase 30A shore power (limited to 25A) supplying the same 120V to both legs.

Hard to provide guidance without additional information. not knowing what you could get on your roof is a major barrier.

What gauge wire is coming down from the roof?

 

[Axe21]

You size the MPPT based on array voltage and output current of the MPPT.

A MPPT 100/50 is a very popular and cost effective controller - kinda their mid-range workhorse.

50 * 14.5V = 725W

Do you fully understand how the 2x120 unit works? It is only a 120V inverter. The only thing it can do with L2 is pass it through to the second panel leg when on 50A shore. It can't charge from it, or boost it or anything.

When inverting, it's like you're on single phase 30A shore power (limited to 25A) supplying the same 120V to both legs.

Hard to provide guidance without additional information. not knowing what you could get on your roof is a major barrier.

What gauge wire is coming down from the roof?

Thank you, I wasn't aware that when inverting its only single phase. I guess I go back to the drawing board and start looking for another invert/charger. Any suggestions that works well with 50amp service?

 

[sunshine_eggo]

Thank you, I wasn't aware that when inverting its only single phase. I guess I go back to the drawing board and start looking for another invert/charger. Any suggestions that works well with 50amp service?

Victron only makes single phase inverters. The 2x120 is a special unit that automatically handles transition between 30A single phase and 50A split phase shore power. You will still get 120V to both legs even when inverting.

Scenarios:
Boondocking: 3000W inverter total to both legs of trailer.
30A shore: 3600W to both legs of trailer. Charge battery with incoming power and pass through power to loads.
50A shore: 6000W to L1. Charge from L1 and pass L1 through to L1 leg of trailer. 6000W to L2 passed directly through to L2 leg of trailer.