FWIW, I usually unhook the FNDC, as I’ve found that it is more suited for a lead acid battery bank. I do have one with a large bank of 16 cell Lithiums and It often does report critically low SOC , so it’s not very useful in my opinion.
Jeremy Rodriguez All Solar Inc. Penrose CO 719-276-4954 Established 1998 On Tue, Aug 25, 2026 at 5:37 PM Jay <[email protected]> wrote: > Hi Zeke > > The lightning is the issue. > > I would replace all the fndc wires, make sure the shunt is clean. And of > course all the cat 5 cables. > > Check every wire connection to every buss. > > Good luck. > > > > > > > > On Aug 25, 2026, at 5:14 PM, Zeke Yewdall <[email protected]> > wrote: > > > > 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 > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org >
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