SI 6048US is a battery inverter that is grid-interactive, can blend battery power with grid. Not hybrid, no PV inputs. Instead it AC coupled to grid-tie PV inverters and DC couples to PV charge controllers.
This is SMA Sunny Island 6048US. Data sheet, manual, system examples under the <downloads> tab.
The efficient island manager Sunny Island 4548-US / 6048-US ► Now with 20 % more power! ► Efficient, simple, flexible and durable! ► Check out now!
www.sma-america.com
SMA is a very high quality and expensive brand. They invented grid-tie photovoltaics, transformerless grid-tie inverters, and AC coupling of battery to grid-tie PV inverters using frequency shift to throttle production.
SMA has lost considerable market share to other less expensive brands, which also move faster to introduce new features. They have three battery inverter series in the US, each with various capabilities. Sunny Island, Sunny Boy Storage, Sunny Boy Smart Energy (a hybrid.)
Sunny Island msrp is now $5700, and retail street price $3700 to $4700. But there are many new in the box old-stock or low hours take-offs due to DC Solar bankruptcy available on eBay, Craigslist, others. You might pay $1000 to $2000 per inverter. They are 120V single phase so you need two for 120/240V split phase, or for for twice the power.
What SI does not do is peak shaving, charging battery to prevent export to grid and discharge to prevent import from grid. That's something many of us in California now need due to net metering being ended. Other models from SMA and other brands offer this.
What SI does best is forming an island grid for off-grid systems with AC coupled GT PV like Sunny Boy, also DC coupled MPPT SCC. And grid-backup, where it sits there with charged battery letting Sunny Boy supply loads and backfeed grid, then letting grid supply loads at night. If grid fails, SI disconnects and runs offgrid.
I've read that many other battery inverters, especially HF, have difficulty regulating GT PV and use a relay to suddenly disconnect them. SI is LF and has no such problem.
For Batteries, there are some 48V batteries on SMA's approved list, others people have used successfully with closed-loop BMS communications. I've read of EG4 Power Pro working, also DIY batteries with some JK BMS. Other people run open-loop with lithium, tell SI it is VRLA.
Filling battery with free grid power at night may or may not work if you operate SI set for "grid as generator" and some internal time settings, or external timer controlling a relay to disconnect from grid.
Likely other brands are better suited to time of use programming like free nights. Possibly Sunny Boy Smart Energy but I don't know enough to consider recommending it. Certainly other brands offer higher surge rating for motors like A/C.
I want (and have) Sunny Island + Sunny Boy for split-phase and 3-phase grid-backup and offgrid systems, but am now trying to get zero export going due to changed utility plan. Since you have Sunny Boy I was trying to steer you to Sunny Island.
Likely EG4 18kpv which you're considering will do what you want, also SolArk and Midnight The One.
Midnight is a highly respected company - their engineers are pioneers of the off-grid PV industry. Unlike their other US made products, The One is made in China for Midnight, not sure how much of its design is from Midnight themselves. New product, even newer battery from Midnight. Definitely worth looking into, but we haven't heard much yet from users.
Since you are on-grid, you can consider putting critical loads downstream of your new battery/hybrid inverter. Or you can use CT current transformers at the utility grid connection and have battery inverter backfeed loads in the house, only when grid is up. There is a thread asking which inverters can use CT and charge from power that would otherwise be exported from GT PV connected upstream; that may or may not be any benefit for you. Usually we want PV downstream of battery inverter so we can operate indefinitely when grid is down.
