Well fudge. In reading specs in more detail, I realized that the Sigineer model does NOT work with the grid. So it will not produce power onto the grid which is a problem. (I'm surprised nobody mentioned that!). OK, back to the list:
I did not understand if you are limiting yourself to UL-listed equipment only and what schedule is driving your request, but if you were ready to consider Sigineer, you may want to have a look at Huayu’s AC-coupled battery inverter as well:
https://m.huayu-solar.com/Content/uploads/2021694206/PDF/AC-Coupled-Quick-Installation-Guide.pdf
As one of the leading 5kw lv ac-coupled solar power inverter manufacturers in China, we warmly welcome you to wholesale high-grade 5kw lv ac-coupled solar power inverter for sale here from our factory. All products are with high quality and competitive price. Contact us for pricelist.
m.huayu-solar.com
My need is similar to that of your friend:
I am looking for an AC-coupled battery charger that will limit itself to charging only with excess solar energy from my legacy grid-tied system after loads have been served.
So (Wbc = battery charger energy):
Wpv > Wld, Wbc = (Wpv - Wld) so no PV energy exported
Wpv < Wld, battery energy is used to supply remaining load power to maintain zero-import (as long as battery energy remains)
With the CT sensors this Huayu AC-coupled charger uses, it appears to support this functionality.
For backup functionality, this 240V model will need to be paired with an Autotransformer and while they have some products with UL listing and are apparently working on getting these AC-coupled inverters listed, that will take some time (which you may not have).
But priced at under $1000 (and possibly under $700), these Huayu inverters are the best budget option I’ve found yet for those looking to convert existing grid-tied systems to zero-export or minimum-export using a battery to store unused solar energy during daylight hours to offset consumption after the sun has gone down..
Victron’s 240V Multiplus II is another option I’m analyzing - pricier than Huayu but top-quality and a fraction of the cost of Solark or Skybox.
And the Schneider Conext SW is another option in similar price range that I am analyzing to understand whether is supports this ‘only charge battery with excess AC-coupled-solar-energy’ functionality or not…
With the changes likely coming to California’s NEM program soon, I suspect that there are likely to be many, many solar NEM customers in California with existing grid-tied systems seeking to find cost-effective ways to store their excess solar energy in a battery for after-hours consumption rather than exporting it to the grid…