My first solar project plan... Please evaluate..

My name is Robert, and I have a camp trailer arriving this month that I would like to outfit with a solar system that I would not have to rebuild anytime soon. I have watched several Will Prowse and Hobotech videos, and am thinking I want to do things a little different than most people do, but am seeking feedback if anything proposed her does not sound workable.

My trailer is an Intech Discover 7'x14' toy hauler, and I will have to replace the power center with one compatible with Lithium batteries. It currently is a 45A load center and I will be replacing it with a 75A Lithium charge converter model. The reason for the 75A model is because it can provide 1000W continuous from the battery bank.

I camp off forest service roads, so will not have shore power often, and will never use the included 11,000BTU roof AC. It's a low profile with side vents only, so I can cover it with solar panels and it can still operate if needed. I will use a small 5000BTU window style AC for hot weather boondocking.

What do I plan on running:
2- DC fridges
1- 1000W Blender for 3 minutes at a time
1- Audio system randomly
1- 27" DC TV for a couple hours at night randomly
1- Diesel Heater for 8 hours a night when cold
1- 5000BTU AC for an hour or so on hot nights to cool it off inside

I also have a Bluetti AC200 power station which has 1700Wh of battery and can handle 4800W surge to get the Blender and AC started, covering inrush requirements.

So what I was thinking is:

1) I can fit three 400W panels flat on the roof rack, connected to 3 of the four panel inputs to a 1200W 120VAC BT or WiFi micro inverter, also mounted on the roof rack for my solar panel system.
2) Feed the 120VAC from the micro inverter into a switch that selects micro inverter OR shore power input to the 75A load center.
3) 200Ah of 12V Lithium battery connected to the load center charge converter with a BT or WiFi shunt.

This would simplify the system into needing these items:
2- 100Ah LiFePo4 batteries
1- Shunt with wireless connectivity
1- 75A Lithium RV load center
3- 400W Mono panels
1- 1200W 120VAC Microinverter with wireless connectivity
1- 2 AC Source 30A input selector switch

So, what do you think?
Thanks for your feedback, Robert

Use link #1 in my signature to input your loads into the downloadable spreadsheet.

Then you can make intelligent decisions on components.

I came up with:
1670 Watts Full Load
3750 Watts Full Surge
2560 Watt Hours Full Load

Also of note, I usually only get full sun when it is directly overhead in the summer as I would be camping in the pines mostly, and in the fall I camp in the open, but may have overcast days.

Something to consider is a deployable array where you can be in the shade and set panels out in the sun.

Looks like you're pretty close on your panels assuming your insolation is right. You can get that number from link #5 in my signature for your location, panel orientation and tilt.

At 2.4kWh, you're shy on your batteries. You'll need at least one more.

I have no experience whatsoever with microinverters.

OK, Thanks for the reply and calculator spreadsheet. The spreadsheet is very helpful.

About the microinverters, the thinking was to simplify wiring by using microinverters to convert the solar panels output into AC right at the panels, and I would be able to use 14awg wire to the inverter charger. I found this diagram showing a possible configuration, except I plan on using the 120V Micro Inverter (or Grid Tie Inverters) and where they show the generator input, that would be my 30A Shore Power plug on the RV.

I know what they are, just no experience with them. That seems unnecessarily complicated and costly assuming you need one for every panel. I assume this results in an AC coupled configuration with the battery based inverter. The advantage I see is that each panel's shading would not impact others.

Link to device?

We usually see grid-tie inverters for fixed applications rather than mobile. That's what I have, string inverters, and now Sunny Island battery inverters which interact with them by frequency shift. It provides grids-backup or offgrid operation during power failures. A reason for grid-tie inverters is they (if high voltage string) don't have to convert 12V or 48V to 120Vac or 240Vac. They accept higher than 240VDC and have thin wires, fewer transistors, saving weight and cost. Microinverters need to do the voltage boost and electronics is replicated in all of them.

Your schematic shows separate 240 VAC branches from grid-tied inverter to battery inverter, and from battery inverter going out (to loads?)
Typically battery inverter has two AC connections. One is from grid (or generator) and other has your protected loads and grid tied inverters there.

"1200W 120VAC Microinverter"
I mostly see listing for smaller 250W microinverters, able to work with a single PV panel. Some module-level optimizers or "rapid shutdown" boxes work with up to four panels. I see at least one 4-panel microinverter:


Moderately low voltage, 50 Voc, so not compatible with larger 36V nominal panels. It obviously connects the four panels in parallel (unless internally has four MPPT), so doesn't matter if they have different orientations as would matter for series strings. What is Voc of your 400V mono panels? My 327W are 65V at 25 degrees C.

Being a grid-tied inverter it will not put out any AC power unless it first sees AC from the grid, or the battery inverter provides it with a local grid. Some (Enphase) have a controller which tells them to generate a local grid for backup/off grid operation.

When grid-tied inverters are used for off-grid operation, they can't just dump all the power available into the wires. They need a method to match their output to what your loads consume. Some do this by datacomm. Mine do it by frequency-shift. If power demand by my house is light, the Sunny Island battery inverter raises frequency toward 62 Hz (like a generator spinning faster), and grid-tie inverters reduce output toward zero watts. Under load, frequency drops to 60 Hz and below like a heavily loaded generator (averaging out to keep clocks and timers correct). Grid tie inverters increase output to maximum available.

The system you're considering - does it have a way to control grid-tie inverter power output? Is Bluetti AC200 power station part of this?

With DC coupling, if batteries run down AC production stops by battery chargers keep working. If all you have is AC coupled grid-tie inverters, their power can only be produced and reach the batteries if AC is available. So mine has a "load shed" relay that disconnects the house, leaving just grid-tie inverters operating.

OK, Now I see what is not workable. I did not realize that I need to see an actual AC grid tie to turn on.

I thought the output of the 4 panel microinverter could feed an inverter-charger directly, and at sunrise, somehow internally see the AC output of the inverter-charger as a grid tie to match to.

I was under the impression the varying AC voltage / current output of the 4 panel microinverter would be directly converted to 120VAC in the inverter-charger for AC loads, with any excess output of the inverter-charger going to the battery bank.

And when the inverter-charger's AC output exceeds the microinverter's input, then the inverter-charger would draw from the battery bank.

And when the battery bank is full and there is no inverter-charger load, then the 4 panel microinverter would shutoff until the inverter-charger uses battery power to supply a load again.

I was planning on using this 1200W 4 panel inverter, using just 3 400W panels:

Pikasola WiFi Micro Solar Inverter 1200W MPPT​