Enphase grid tie add battery

[derbuechsenmacher]

Last year I installed an additional 9kw to my existing 11kw solar setup. The new system uses enphase micro inverters. I am considering adding battery to the system and I know I need to do an ac coupled system. I've read tons of forum posts and watched countless videos. From what I can tell, I essentially have to feed the enphase 240v output into another inverter/charger which would charge the batteries (the enphase basically is the grid input) and then have the new inverter connect to the panel. Am I remotely close here? How do I ensure that the batteries feed power to my house instead of the grid? I'm assuming that I really need to connect the new inverter in parrel with the enphase since the enphase won't output unless it sees power from the grid. I don't want to go with the enphase battery system as it seems to be overpriced. When determining to go with the enphase grid tie system, I did evaluate whether to just build it off grid, and the enohase system was onlu about 3k over the dyi and I did not have to do any of the work (yes I could have gone cheaper on the dyi components, but I speced the best I could find since reliability is critical). I dontt have what I speced handy (can't find the docs on my computer). So please don't ask

 

[chrisski]

Am I remotely close here?

You're on target.

How do I ensure that the batteries feed power to my house instead of the grid?

It won't feed loads power to the grid uness there is excess. Some loads you select are moved to a critical loads panel. Check the AC coupled inverter to find strategies. Strategies are important espcially for NEM3 and TOU rates.

I am DC coupled and I would like my inverter to sell 3 kW/hr power back to the grid from 7 pm to 10 pm to cover my Esla Charging, but my inverter can't do that. I can have my inverter remove my critical loads panel from the grid and be powered by battery and solar during peak hours.

With your AC coupled system, if power is lost, be sure it has a way to continue to charge the battery. Not all do.

I've seen pics of a local to me Enphase Inverter and battery install.

 

[derbuechsenmacher]

thanks. doing a bit more research seems to indicate to not parallel the inverters and to put the new inverter between the existing enphase and th grid. this way the new enphase provides the grid ‘signal’ to the enphase so it would continue to charge in a grid down setup. i am a bit confused in that some inverters will change the frequency to shut off the enphase (fake it to think the grid is down) but i would think that once the batteries are full, if there is no power draw the inverter would simply stop charging the batteries. perhaps the frequecy shift is so that no power goes out to the grid, but i would think that someone would make a smart switch that would shut off if there is jo grid power. isnt that what a generator transfer switch does (turn off the grid and start the generator and when the grid is back turn off the generator). all i want to do is essentially run the generator always (generator here being the solar setup) and cut off the grid when its down ??? just thinking outloud here

 

[BentleyJ]

A hybrid inverter will have a built in transfer switch (utility disconnect) that opens and disconnects the grid from the AC Input terminals on the inverter. With a critical loads subpanel the battery inverter continues to supply power to only those items that have a breaker in the subpanel. The main panel gets disconnected by the inverter.

Its also possible to do whole home back-up at the main breaker panel by installing the inverter between the utility meter and the main breaker.

Enphase has a back-up battery system which requires a utility disconnect switch in case of an outage.