William, I have had the same frustration with attempting to train customers to monitor voltage, and to treat SOC with suspicion. Some people are capable of getting it, some just aren’t. Off-grid life is tougher for those folks, and for their solar contractors. “I don’t understand why I lost power—the Trimetric says 75%!” “Have you looked at at the voltage?” “The what?”
Part of the problem is that we as consumers have been trained to believe the SOC numbers on our smart phones. I know I believe mine. We just got an electric car and same deal. Went on our first road trip, and of course had no choice but to manage charging based on the nice percent numbers on the screen. But in both cases, those devices seem to track battery state reasonably well. Too bad solar battery manus can’t do whatever Apple and Volkswagen et al can do. Bruce Erickson Mendocino Solar Service 707-937-1701 PO Box 1252 Mendocino, CA 95460 "Serving the Solar System" > On Feb 9, 2024, at 8:05 AM, Drake Chamberlin via RE-wrenches > <[email protected]> wrote: > > How does the lack of accuracy in SOC detection affect the usefulness of > closed loop systems? > > > Drake Chamberlin > > Athens Electric LLC > > Ohio Electrical Contractor’s License 44810 > > NABCEP Certified PV Installation Professional > > > > On 2024-02-05 11:36, William Miller via RE-wrenches wrote: > >> Jason: >> >> I am careful about getting my clients too dependent on SOC readings. SOC is >> a calculated value based on changing variables and is notoriously inaccurate. >> >> Below is a screenshot of the Optics reporting for a client. The graph line >> that begins as the lower of the two is the SOC, the other is voltage. The >> SOC is out of calibration until about noon when it jumps from about 20% to >> about 80%. This does not mean the SOC changed by that amount, it means that >> it was just very wrong. Who knows when it is correct? >> >> In spite of repeated entreaties this client still reads the SOC and becomes >> concerned when it gets low-- even if the voltage level indicates the >> batteries are well charged. I have to deal with his misplaced anxiety. >> >> >> <image003.png><image007.png><image001.jpg> >> >> This problem appears to occur across all battery/inverter technology. For >> example, SMA touts their "coulomb counting" as more accurate than others but >> I have witnessed otherwise. You'd think that BMS units built by lithium >> manufacturers for their own products would be consistently accurate but even >> those BMS units need to recalibrate frequently, this according to the >> battery manufacturer's engineers. >> >> It would be nice to offer clients a simple, accurate method of ascertaining >> battery charge levels. SOC is not that method. I train my clients to watch >> voltage levels and to understand these values are elastic. If you can see >> trends in the battery voltage, so much the better. This is why I like the >> Outback Optics interface. This is also why a good AGS system examines >> battery voltage over time. >> >> I no longer install Outback FNDC units. Without them there is no SOC >> reading. I don't install Sunny Island systems—they are SOC centered and >> suffer for it. >> >> William >> >> Miller Solar >> 17395 Oak Road, Atascadero, CA 93422 >> 805-438-5600 >> www.millersolar.com <http://www.millersolar.com/> >> CA Lic. 773985 >> >> >> From: RE-wrenches [mailto:[email protected] >> <mailto:[email protected]>] On Behalf Of Jason >> Szumlanski via RE-wrenches >> Sent: Sunday, February 4, 2024 7:30 AM >> To: RE-wrenches >> Cc: Jason Szumlanski >> Subject: [RE-wrenches] State of Charge Meter for Sol-Ark >> >> Are there any off the shelf solutions to view battery SOC via a wired meter >> mounted remotely on a property? I have a client with a simple voltage based >> meter for lead acid batteries that they are accustomed to using as a quick >> and approximate gauge of SOC. They want something similar for their new >> Sol-Ark with EG4 LL batteries. >> >> They will have smartphone app visibility, but they want something they can >> see inside the house without picking up a phone or going out to the >> inverter. Ideally the SOC will come from the inverter or the battery itself, >> not an external source (to avoid discrepancies). >> >> Jason Szumlanski >> Florida Solar Design Group >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> <http://re-wrenches.org/> >> >> List Address: [email protected] >> <mailto:[email protected]> >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> <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]/ >> <https://www.mail-archive.com/[email protected]/> >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org> >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> <http://www.re-wrenches.org/etiquette.htm> >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org <http://www.members.re-wrenches.org/> >> > <image002.emz><image006.emz>_______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > <http://re-wrenches.org/> > > List Address: [email protected] > <mailto:[email protected]> > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > <http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org> > > There are two list archives for searching. 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