Advice and Planning for a 44kWh Battery Backup + Solary

[cschill2020]

Hi,

I am located in San Jose, CA. I am working on building a battery backup system. I have 44kWh 48V LifePO4 batteries with Seplos BMS.
I have a 100A subpanel handling critical loads that is currently utility powered. Max power from that panel is ~3kW @ 120V ~= 30A. No 240 yet... In phase 1, I would like to connect the batteries as a backup source to the subpanel using a hybrid inverter.

Now the next piece of the puzzle is where I would like some feedback. Which inverter/charger would you recommend for this setup? I am currently considering starting with a Victron Multiplus-II 5kW and potentially adding a 2nd if I need 240V (e.g. adding an EV charger).

Phase 2 is adding solar to charge the batteries. I can easily support 25 400W panels, but I would probably start with ~6500kW, 16 panels (4S4P). So I want to add a Victron MPPT 250 controller on top of this. Any other considerations I should have for such a system?

I talked to a rep at a local solar equipment company and they mentioned that I may run into issues with the utility (PG&E) for such a system. The rep suggested looking at a grid-tied inverter like Tigo. I guess one of the issues with Victron is lack of UL certs. In any case, I am not planning on feeding the utility given current NEM3 rates. Victron and Seplos are compatible. I am not sure about Seplos and Tigo compatibility...

Finally, I am not sure what all I should be considering with respect to distribution and fusing. I am looking for resources on what additional components I should consider on top of the inverter and MPPT.

Thank you!

 

[G00SE]

If you haven’t purchased the charge controllers yet, Victron does offer some 450v capable units. This may help you get a higher string count than the 4s4p you are planning.

 

[Brucey]

I believe the 5kVA multiplus 2 will have UL listing at some point. I didn't think you could get approved for diy batteries in California.

If you need 240V in the future potentially consider a Schneider 6048 /xw pro or similar, delivers 120/240 from a single inverter.

 

[pvgirl]

I would not recommend Victron products for fixed installs, as few of the products are listed to the appropriate UL standards, and even those that re listed are missing features needed for a code compliant installation(no arc fault, or conduit connections on charge controllers). Sol-ark and Schneider have high quality listed products.

Keeping your setup as code compliant and permitted as possible will limit issues in the future, such as when you sell your house, or have other permitted/inspected work done on your house.

 

[zanydroid]

I didn't think you could get approved for diy batteries in California.

You can if you use recycled EV packs and put them in an outbuilding meeting certain clearance requirements.

 

[zanydroid]

Keep in mind there are very specific rules for battery placement, size limits, and protection in California (well it’s shared with other states but California is a bit of a pioneer) so make sure you understand these before you get too far in the project.

 

[cschill2020]

Thanks all. This is helpful. I think I will likely go with a Sol-Ark 15.

 

[n2aws]

Keep in mind there are very specific rules for battery placement, size limits, and protection in California (well it’s shared with other states but California is a bit of a pioneer) so make sure you understand these before you get too far in the project.

LOL. I was reading through this thread, and your comment made me chuckle. "California is a bit of a pioneer" is a great and politically correct way to say they're insane.