12v oem system with 400ah battery and then adding EG4 3000EHV-48 to shore power input

[c473]

Wanting to add extended boondocking capability to the travel trailer.

I can add capacity to oem 12v system (which has a lifepo4 charger) with a 400ah battery right next to the panel, less than 2 foot cable run.
Should I have two "independent" systems by adding an EG4 3000EHV-48 (with a 48v 100ah battery and 1500 watts solar) and wire the inverter output to the distribution panel and the shore power to the inverter a/c input? Or just have two 48v batteries and letting the oem 12v system run off of the inverter and living with the inverters idle consumption but having increased capacity for running ac fridge and air conditioner?

Writing this out makes me think putting in a smaller 100ah 12v and 2 48v batteries would be a better solution.

So the 12v battery would really only be useful if the 48v batteries were depleted and there was no/insufficient solar, like night time, so we'd still have lights and water.

Where am I going wrong?

Thanks for any advice/insight

Chris

 

[justinm001]

Here's what I did. I have a 10kw 48v system that runs a pair of quatto 5000w in split phase as my main system, then put a 12v quattro 5000w with 10kw batteries also. Put all my solar on 48v. I split my loads so an ac and a heater along with a few outlets are on 12v but the other ACs, heaters and everything else is on 48v. I then have it set so one of the 30a breakers from the 48v goes to the 12v.

If I'm on shore I just turn the 12v inverter to normal mode and when on batteries I turn it to inverter only. I then select the loads based on batteries and can just switch from the 12v AC to the 48V.

If the 48v gets full I can turn on the 12v inverter and it'll just convert DC to AC to DC which is only like 10% loss then it'll pull from one to the other.

Victron is unique as it has poweassist so I'll usually set my 12v input limit to 12.4a (lowest it allows) and run the AC which is like 17A. This pulls 12.4a from 48v and 4.6a from the 12v then with my other loads they seem to deplete evenly.

Super happy with the setup as everything just works and if I have any issues I can just use the other bank and deal with it when I get home.

 

[sunshine_eggo]

EG4 is going to increase your load by 40W at all times. If the goal is to extend the usable capacity of the 12V system via 48V battery:

MPPT for solar to 48V
DC-DC charger from 48V to 12V (including a wide input 30-60V to 13.8V converter - cheap).