Hello @BLUETTI
Last weekend, I noticed some strange behavior with the EP600. Due to a mistake on my part, I blew the main fuse, and the automatic transfer switch switched to backup, as expected.
But I also noticed that, due to the transfer switch switching over, my AC-PV inverters are no longer connected to the grid but to the EP600’s backup line (inverter output to inverter output!).
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OK, to prevent any issues, I switched the AC-PV inverters to “Zero Export” and expected them to supply the house’s base load but not feed back into the EP600.
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However, I observed some unexpected behavior: the EP600 apparently uses an undocumented “reverse charging” mode. My AC-PV inverters did NOT (!) reduce their output to the home’s base load, but instead generated power at full capacity, because the EP600 was charging the batteries via the backup circuit!!!
Is that even possible? Does the EP600 actually have an internal circuit that enables “reverse charging,” or how else does the current flow from the EP600’s backup side back to the B500’s charging electronics? Technically, the B500 should be supplying power to the EP600’s inverter, which in turn powers my house… but what I observed was exactly the opposite: my “house” was reverse-charging the batteries.
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The AC-PV inverters naturally switch offline immediately during a power outage, exactly as required. But as soon as the EP600’s emergency power kicks in, the AC-PV inverters reconnect to the “grid” and go back online.
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P.S.: I’ve since installed isolating relays that completely disconnect the AC-PV inverters during a power outage; they then remain offline. Still, I found this behavior “interesting.”
Or is this behavior technically possible, and am I actually allowed to charge the batteries via the backup line during a power outage?