Can this even be done? Or is it a stupid idea? Off grid design with grid charging...

[tpa_pub]

Newbie, and have been doing my research, but I have a design concept that doesn't seem to fit any of the use cases I"ve run across. For a variety of reasons, I'd like to build a solar/battey "off grid" configuration for my home, but use grid/generator for supplemental charging:

• Home currently consumes from 50-100KwH per day (no insulation or drywall, home is being restored. Essentially a barn)
• Est. use after home is completely restored 30-50KwH per day.
• Due to the restoration, there will be a time period where grid electric will need to be disabled. Will need to run 100% off batteries for that time.

Other considerations:

• Hurricanes (Florida)
• Would rather not deal with battery/solar grid tie complications with the utility
• Sell back is only .02/Kwh, not enough to make me want to deal with the utility
• I'm ok with a $50-75 electric bill per month future state
• Will likely have to deal with utility for the generator tie
• Generator already owned, but not installed. 20kw air cooled natural gas
• Whole home (ac, electric oven, etc.) in scope for battery power/inversion.
• Gas heat, gas tankless water, 3ton ac, 16-17 seer
• I'd like to be able to support 100-150 amp scenarios (air compressor, welder, etc.)

My thought was to buy 45-60kwh worth of DIY (thinking Basen Green, since they've added the active equalizer it seems like a decent setup) LifFePO4 arrays, and initially cable it and a 15-18kw, 100+A inverter to my newly installed main load panel. Use the generator/grid tie panel from the generator vendor to supply power to a charging circuit, with circuit breaker in my outdoor grid tied load center to feed a charger for the battery array. Once I can get some solar panels installed (can likely only install 12-15kw worth on my roof), they would be introduced to the inverter.

The idea would be to recharge the batteries with grid overnight until I can get the panels installed, then use grid to potentially supplement the panels long term, but only as a charging source overnight (I can subscribe to an off peak plan that offers the lowers Kwh costs at night). During the period when I have to have the grid disabled for the renovation, I could either use the generator (not great, as hate to put the hours on it), or run 120v/15a power for charging from a neighbor (not a great option either, but theoretically if I can keep battery use in check, it should keep up if I keep usage to under 40kwh/day, right?)

Does this make any sense, and if so, how to go about it from an inverter charger perspective? It would be awesome if I could find an all in one that could support this model, but the grid connections would have to be for charging only, not for feeding back in.

Or is this just the dumbest idea ever?

 

[DIYrich]

Gridboss plus two flexboss21.

If you are using 50-100 kwh per day, you probably need more than one 12-15kW inverter.

You could do it with multiple 12000xp, but the gridboss simplifies the connections.

 

[Skid]

My system is much smaller using the grid to charge a 12v 100ah battery via an all in one inverter. The grid only enters the AIO to charge the battery, the inverter output only connects to the house circuit which is isolated from the grid and the house runs solely off the battery. The efficiency losses are offset by power costs of about .04/kwh. Very easily done. The same will go for yours, simply scaled up.

 

[TM48]

No point in using grid to charge batteries each day. Less expensive to just let grid power the load until your panels are installed. You may wish to cycle your batteries occasionally to keep them balanced maybe every month.