Please help me design a reasonable setup for my tiny house

Hiall!

I'm starting a design phase for my tiny house. The property is connected to the grid, but I decided to go for a solar setup.

I Am looking into following functionality for my solar setup:
- Solar to charge my batteries (bank of 2 LiFePO4), my electrical consumers will be 12V DC as much as possible.
- I will require tools to run off 220V, so the setup requires an inverter.
- When consuming 220V, the power should come from the batteries through the inverter, NOT from the grid.
- When batteries get empty, the power should switch to the grid and continue to run my 220V.
- Empty batteries should get charged from solar, NOT from the grid.

I Am currently eying following components:
Solar: 2x Polycrystalline Solar Panel 150W 12V (approx. 25 Amp.)
Batteries: 12V (pack of 2 LiFePO4, parallel)
Battery charging: Victron BlueSolar MPPT 150/35
DC/AC Inverter: Victron MultiPlus Compact 12/1600/70

My main question for now: If I'm not mistaken, the Victron MultiPlus Compact 12/1600/70 is almost always used to supply 220V as I require, but when batteries need charging, it will use the grid to charge. This is not desired by me: I want to establish priority to the solar panels for charging. Can this be done with the components I have listed?

Thanks in advance and have a great, SUNNY day!
Cheers, Igor

IMO I think you would be better to just forgo all the nonsense and just get one of these.


It will tie into the grid... charge the batteries from the solar or grid (programmable) and handle your 240 volt demands.

And I think it will cost about the same but I think less setup hassle and offer more output watts as well.

the mttp 150/35 is $300 alone on amazon

your DC/AC inverter is $1200 on amazon (well something similar anyway I can't find that model.)

the MPP unit that will do it all is $1330 + $268 shipping.

All that being said I think you might be a little under sized on the panels and batteries but I don't know your power demands for the 220V.

Will did several great videos on the MPP if you haven't seen them.

Hi naelr, thank you for your suggestion!

I have indeed seen such all-in-one MPP stations and looked into their possibilities closer (Also saw Will's videos indeed). It was my go-to thinking until I found a source close by who is selling their over-stock (they quit solar and focus on other core business areas now). I can acquire both Victron mpp and inverter for just over 150 dollar.

I know I could just get them and re-sell them with profit, but I don't have the money up for grabs and need to be very careful in my every-day budget.

I still like to know: can the Victron MultiPlus Compact 12/1600/70 be programmed to take the load from the DC batteries and NOT from the AC grid?

Thanks again and have a great, SUNNY day!
Igor

I honestly don't know the answer to that question and will gladly wait for someone like @Will Prowse to step in with great knowledge. Good for you. You could; however, get them cheap and up sell like 10% and help out this community!!!!!! I might be interested in something you can acquire.

I would like an inexpensive source for LiFeP04 batteries of any kind.

You could perhaps put a manual cut off on the AC side and only allow it to get AC when you want it to get the AC. Just a breaker in the panel is all this would take.

Inverter Manual is here: