Trying to troubleshoot an outback FNDC that's giving completely wacky SOC readings. Yet the current readings all appear to be reasonable. We just replaced the FNDC because of a lightning strike -- came in through the ethernet to the mate it seems (took out a router too), and took out the mate3s, hub10, and possibly the old FNDC. So all of those are new. Rest of the system is maybe 5 to 6 years old -- four radians, four FM100's, 1200AH of 16 cell LFP batteries (open loop). Has been operating pretty well for the past few years other than some battery BMS failures. About 6 weeks ago, it looks like the SOC started being completely wrong on the old FNDC as well... which makes me question something about wiring... a wire coming loose from the shunt or or ??
Whenever I do a spot check for amperage from it, it looks right. But then it bounces from 100% SOC to 2% SOC in one hour... physically impossible. And then, I drain 23kWh out of the batteries, and it stays at 100% SOC for the next 6 hours. Recorded voltages also look good during spot checks, and for the recorded min-max on the graph (not sure if those are from the FNDC or the inverter though). System is operating fine, as long as I do all controls based on voltage, not SOC. Of course the system is 2500 miles from me, so I'm also trying to troubleshoot remotely. I did ask outback tech support, and was surprised to get an answer back... which turned out to be completely useless. They said the FNDC only works with lead acid batteries, and lithium batteries are used in closed loop. Nevermind that I have well over a dozen radian systems with lithium batteries and FNDC's working correctly, and this exact system was working correctly that way for 5 years. Zeke -- Zeke Yewdall PV Engineer NABCEP #031508-89 [email protected] 303-523-3592
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