[RE-wrenches] Dual radian system stopping selling on sunny days

[Tyrone Houck]

Forgive me if I'm missing something but typically I would have sell voltage
slightly higher than float and lower than absorb.. I also never use the
FNDC for charge termination and instead let the charge controller do
everything by voltage... this may be a slightly different logic for lifepo4
but has always worked great for me for lead acid and agms.
Best of luck!


On Fri, Sep 26, 2025, 10:52 AM Dave Tedeyan via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> To the Outback extraordinaires,
>
> I've got a dual radian, grid tied system that has been in service for
> about 9 years. Recently, it has started this behavior where it will stop
> selling to the grid on sunny days. Looking back at the data, this has
> happened intermittently and very infrequently a couple years ago. But now
> we are at the point where it happens every sunny day. Once the batteries
> get up to fully 100% charged (not 99%), the selling stops and the system
> only harvests enough solar to cover the backed up loads.
>
> I got a hold of the USB card data. It appears that the inverter goes from
> "Sell Enabled" to "Offset" when this happens. I cannot tell whether the
> inverter randomly decides to switch mode and then stop selling, or whether
> it is the stopping selling that puts it in "Offset" mode. The sell voltage
> is set at 52V, and float is set to 54.4V. It looks like the batteries are
> generally sitting around 54V when this happens. Once the inverter enters
> "offset" mode, then the battery voltage stays steady at 54.0V
>
> Does anyone have any idea what can be causing this to happen?
> Cheers,
> Dave
>
> --
>
> [image: Logo] <https://www.sungineersolar.com/>
> Dave Tedeyan, P.E.
> Owner | Sungineer Solar
> p: he | him | his
> a: 1653 Slaterville Rd.
> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>
>
> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>| Ithaca,
> NY 14850
> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>
> w: www.sungineersolar.com <http://www.sungineersolar.com/>
> c: (607) 270-0370
> _______________________________________________
> List sponsored by Redwood Alliance
>
> Pay optional member dues here: http://re-wrenches.org
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> 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/re-wrenches@lists.re-wrenches.org/
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20250926/30edbd29/attachment.htm>