Elbow Posted December 9, 2019 Share Posted December 9, 2019 Hi, Last night I was woken up at midnight with my inverter beeping. Went to look, muted the alarm and all seemed OK. But this morning I see my servers rebooted at that time so its clear that the inverter dropped my essentials loads (and then restored them immediately). My server, NAS and two Pis all restarted. Now normally this works fine - when the grid goes off the inverter seamlessly switches to the solar and/or batteries. My inverter is programmed in Grid tie with backup mode. I have set the battery discharge threshold with grid is present much higher than the threshold when the grid is not present. I also limit how much power is taken from the batteries when grid is present. But it seems like these two discharge thresholds don't work properly? My batteries normally discharge down to that "grid present" threshold in the evening and the inverter then switches to powering the essentials from the grid. I think that what happened was: Batteries were at or just below the "grid present" threshold Grid dropped. Inverter logic is flawed and it dropped the loads because the batteries were below the "grid present" threshold. And set off the alarm. Then it noticed the grid gone and switched in the lower threshold since there was no grid and turned the loads back on but now from the batteries. So it looks like this: (The "Grid watts" between 00:00 and 02:00 is misleading since my ET112 has no power do can't be queries to get the data - that's why there it doesn't show 0 - no readings) Zooming in: The power loss was probably shorter that the 10 minutes here - when the inverter dropped and restored the power the EmonPI and other gear had to reboot so measurements were lost. Did anyone using the Infinisolar or other OEM stuff similar to this have this happen? Any ideas as to how to sort it out? My NAS especially doesn't enjoy losing power - it will now spend the next 11 hours resynchroning its RAID, so I'd like to avoid this! Thanks! Quote Link to comment Share on other sites More sharing options...
Coulomb Posted December 9, 2019 Share Posted December 9, 2019 (edited) I've always wondered how hybrid inverters are supposed to achieve a smooth transition from grid to battery power. Power generators switch off; a suburb or town worth of loads is still connected in parallel with your loads. The inverter has no hope of running the whole town. So the output volts goes to nearly zero on the essential loads. The inverter notices this, and disconnects the AC-in (the now-dead grid) from AC-out (your essential loads). The relay takes about 10 ms to drop off. Now the inverter is capable of running your loads, though briefly it was massively overloaded, so it takes a few milliseconds to come back up and settle down. So your essential loads see maybe 20 ms of down time, maybe more. How they react to this is a matter of how much energy storage (in electrolytic capacitors, presumably) they have on-board. Of course, you could put a UPS between the hybrid inverters and the essential loads, but who wants to do that? You could configure the hybrid inverter so that its topology is double conversion, but that adds a lot to the cost, more to go wrong, and adds losses. I hope someone is able to explain how it should work. Meanwhile, I'm happy enough with my Axperts. Edited May 12, 2020 by Coulomb Quote Link to comment Share on other sites More sharing options...
francois Posted May 11, 2020 Share Posted May 11, 2020 On 2019/12/09 at 11:24 AM, Elbow said: My inverter is programmed in Grid tie with backup mode. I have set the battery discharge threshold with grid is present much higher than the threshold when the grid is not present. I also limit how much power is taken from the batteries when grid is present. Hi @Elbow, Could you please share how you did this? I have the latest version of Watchpower where I can set the limit on the Amps drawn from the batteries, but because I have PT's and the inverter is not reporting the correct battery values, this does not seem to work for me. Regards, Francois Quote Link to comment Share on other sites More sharing options...
___ Posted May 11, 2020 Share Posted May 11, 2020 On 2019/12/09 at 1:29 PM, Coulomb said: I hope someone is able to explain how it should work. Meanwhile, I'm happy enough with my Axperts. That's exactly how it works. The input is disconnected, but for a couple tens of milliseconds there is a massive "overload" on it. It's not quite zero-volt territory, it disconnects as the voltage sags below 180V... but it is serious brown-out territory Quote Link to comment Share on other sites More sharing options...
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