Inverter building using Wiseguys Power board and the Nano drive board

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KeepIS Guru Joined: 13/10/2014 Location: Australia Posts: 1688	Posted: 02:21am 22 Apr 2024         analog8484 said    It seems even most commercial inverters have issues using only voltage monitoring of lithium batteries.  Most of them need true SOC monitoring via closed loop BMS integration to work reliably. Hi, I wanted to add a bit more context as I was heading out when I posted: Any commercial inverter trying to Monitor LiFePO4 SOC with only voltage is obviously crazy! If that is indeed what they are actually trying to do. But like everything - on line forums make these generalized statements, but exactly are they trying to monitor? Like you, I also heard these statements and numerous other half truths and simple throw away lines about LiFePO4 Solar and Inverters. The inverter is simply looking for an accurate voltage where a LFP battery is getting to a low % of charge - Very hard to do if you are aiming at values around 50% to 60% SOC, you can't do this if you don't know the current Load conditions, and it depends on the battery capacity for that load, and the temperature, etc on and on. However this is why these online statements are all generalized white noise to me. If you know your system and power usage, and you know the loads that it will be running under, and you have plotted the discharge cycles over a period of week or months (year in my case), then you know the lowest voltage that the Battery bank will drop to under these running conditions - you can accurately set a low voltage cutoff point for you system. - And that is a simplified statement in itself! Obviously you will know the period of time this "Low voltage measurement" has to persist before initiating an Inverter AC stop condition.   The restart voltage is a bigger problem - obviously - and conditions like the Bulk Charge rate that you are subjecting the Battery bank to will drastically affect the ability to determine if the Bank has sufficient charge to be reconnected by voltage state alone. If the inverter shuts down at night - it's not going to recharge from solar, it's not going to turn back on. But that again can be done if you know the system state when charging. How do I answer the question - Yes - my system can work by monitoring voltage alone, but I know exactly what this system does, it records and graphs every current transient, ever voltage fluctuation with load and charge, it records every second of every minute of every hour, 24 hours a day 7 days a week.   So the answer is Yes and NO - it depends!