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August 29, 2026 2:41 pm
I have a 2 Flexboss21 inverters. Only one exhibits a strange issue of toggling a relay for several minutes at a periodic rate of 1 to 2 seconds. I don't see the purpose of toggling a large relay every couple seconds. It most often happens when the battery bank reported SOC is right at the selected Battery Backup Mode: Backup SOC%, just an observation. The other Flexboss21 never exhibits this issue. Also, ALL components have a finite service life. Whichever relay it is seems doomed for a premature failure at some point. To me this behavior is like a software hysteresis issue.
I have the latest firmware installed, FAAB-2727.
Has anyone else ever experienced this?
August 31, 2026 4:53 pm
I've got relay cycling on my unit when it is running in SOC mode and the battery gets full. Here is a YouTube video I made about the relay cycling I get so you can see whether it's the same as what you have. I switched to running everything voltage-controlled instead of SOC-controlled to avoid the relay cycling.
There is also a very long thread on the DIY Solar Forum if you want to read through that to see other people's experiences.
The 2727 firmware is a bit better than earlier firmwares but it definitely still has the issue.
