Augmenting existing solar with Multiplus

Q&A and troubleshooting
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1

I have a house with an existing Solaredge solar system (10KW.) I am on a TOU rate with a municipal utility that allows for net metering, so there’s a period of time that I can backfeed the grid and get paid 12c/kwh.

I am looking to add battery backup as overhead power lines and tall pine trees (and a spouse who worries) result in (on average) 1-2 outages a year.

I’d like to:

  • Leverage solar to charge the batteries during outages (extend runtime) or at least supplement power provided by a 2 multiplus setup (for split phase power.)
  • Use a meter socket adaptor, so the system is powering the entire house without a subpanel. Fully expecting that in an outage I will have to manually shut off loads that I don’t want to drain the battery.
  • Allow for scheduled charging from the grid, and backfeeding the grid. Seasonally the “peak” power period change, so I would need to put this all on a schedule.

Ideally, I’d like to also be able to supplement with a gas generator; but this isn’t so important. My current generator setup is that I roll it out from the garage, then I have an interlock that I flip and turn it on. If I could also add a port to the multiplus to let it charge the batteries that would be better - since I could potentially then get the benefit of a non-inverter generator combined with the pure sine wave output of the multiplus (so cleaner power for non rectifed loads.)

I think most of this is doable.. I’m looking at other options as well, but many of them are crazy expensive and don’t provide a ton of flexibility.

The two things I can’t figure out are:

  • Will the multiplus/quattro will backfeed the grid (scheduled discharge) .
  • If the batteries are full, and there’s no utility to feed excess solar power to, what will happen to the excess solar generation? Will the multiplus handle that?

Separately, I don’t have any “unfinished” spaces in my home - pretty much all of my basement has HVAC registers and returns. I’d prefer to put the batteries in the storage room of my basement, but it is a heated/cooled space. Is that a problem? I’ve been told that I can put batteries indoors, but not in “habitable” spaces.

Thanks!

2

If you want, yes

In case of DC coupled PV, they simply follow the charging voltages, no difference to mains available.

In case of AC coupled PV, the MP would need to raise the output frequency, in order to signal to the AC PV inverter to reduce power. This means the AC PV needs to be able to follow a P/f curve.

You are essentially looking for an ESS, so the ESS manual is a good read