Backup power from solar batteries

[AndyS]

Hi. I just replaced my solar inverter with a (hybrid inverter + battery) pack. It comes with backup functionality so I naturally connected my house most critical circuits to the inverter's backup port. The functionality works great - I turned off grid supply to the house and the backup loads did not even notice. But then, to my big surprise, I found out that if the inverter is malfunctioning or rebooting or updating firmware, it will stop supplying power to the backup loads. With this setup my critical circuits will survive the blackout but will lose power if something goes wrong with the inverter. Considering that last blackout here was more than 10 years ago, I'm much more likely to lose power due to the inverter malfunction than a blackout. Eventually I flicked the changeover switch (which was part of the installation) to move my backup circuits to the grid supply.

My question is - do all inverters work this way? My expectation was that the backup port has a hard connection to the grid inside the inverter, so even if the inverter is completely shut off, the current would still flow from the grid to backup loads. And if the inverter operates normally and detects the grid outage, then it would switch backup port to the battery.

[solardreamer]

It depends on the inverter system. If you have an all-in-one system then what you observed is typical. Other systems support an external switch/gateway (e.g. Tesla Gateway, Schneider BCS, etc.) that can automatically power loads from the grid when the inverter power is not available for maintenance or malfunction.

[AndyS]

If by "all-in-one" you mean inverter and batteries come as one system then yes that's what I have. It's an Anker Solix X1 system: X1-H12K-T hybrid 3-phase inverter with six X1-B5-H battery modules. So you are saying that if I got something similar from another vendor it would work the same way? Kind-of defeats the purpose of a "backup". Only useful in the areas where a blackout is more likely than the inverter not running normally. Or to be more accurate, the backup functionality itself is useful, the automatic switchover from grid to battery in case of a blackout is not. Like I said before I flicked the changeover switch and my backup circuits are now powered from the grid, and in case of a blackout I can flick it back and the circuits will start getting power from the battery. But it's a manual procedure now, and my critical loads will lose power temporarily and reboot. Not what I was expecting when I was getting the battery...

[solardreamer]

I was mainly referring to the common (cheap) all-in-one's. I don't the specifics of Anker Solix X1 but it looks a bit better than the cheapo's. So, you may want to check with Anker to see if it provides a UPS mode. Basically, you are looking for a UPS (with much bigger battery) for your home.

[AndyS]

Ok thanks, I've done some research now. Should have done it before getting the battery. I actually did, but not on this particular question, did not expect the backup would work the way it does. Turns out the "big" brands are the same. SigEnergy and Sungrow are ones of the most popular batteries here in Australia. They have what they call a "full home backup", but it works exactly the same. It's a backup port/terminal on the inverter which gets automatically powered from the battery in case of a blackout, but also gets deenergised when inverter is not operating normally.