[RE-wrenches] BASE Power added a battery to my solar customer's home and I'm concerned this not a safe design

[scot.arey at solarcentex.com]

Greetings Wrenches.

Here in Texas we have this new company called BASE Power, started by Michael Dell's son (of Dell Computer). Their biz model is to install energy storage at people's home, have that person sign up with them as their retail electric provider, and gain backup capability to the battery's capacity unless the BASE team is discharging the batteries remotely to make money on high wholesale prices. I'm trying to figure out their financial model to make this work but he has smarter guys than me.

Here is the issue: BASE installed whole-house backup but left my SolarEdge grid-tied inverter on backed up side but there is no communication capability from their system to mine and I'm not sure this is a safe design.

We have a SolarEdge 11400, grid tied with point of interconnection as line side hot taps. The BASE guys re-oriented the entire main service through their GroWatt 200A auto transfer switch and this means my SE11400 is on the backed up side. The ESS is 50kwh and two GroWatt 11400. There is no comms or AC coupling from the GroWatt to the SE11400

Seems to me if the grid fails at midday with batteries at 100%, and the SolarEdge cranking out 9 or 10KW, there is no place for the solar production to go (batteries are full and assume the house running at typical 3KW). If this was properly AC-coupled, then full batteries might prompt some frequency shifting to bring the SE11400 lower on output, but there is nothing to do that here.

This reminds me of customers who install generators and then their gen guy says he has this solar all figured and puts my solar downstream of the generator backup such that the solar is backfeeding to the generator.

Do I have this same scenario? What will happen to this house if grid goes down, batteries are full, and the solar is maxing out? Will the SE11400 induce such a voltage swing that it eventually drops off line? Is this self-correcting that this is a reliable design. My gut feel is not at all but wanted to hear what you thought.


Howard "Scot" Arey
Owner, Solar CenTex

NABCEP PV Installation Professional
TECL 29755
254-300-1228
[cid:5ef75353-fc63-49a1-a18c-2e250b8a09a4]

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