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

[Tyrone Houck]

It's also worth considering temperature compensation and how that may
affect the dynamic...also the CCs float and absorb should be set slightly
higher than the inverters. Regarding offset behavior, here is an
application note that may help..

https://outbackpower.com/downloads/documents/appnotes/offset_tech_note_correc.pdf




On Fri, Sep 26, 2025, 8:23 PM Tyrone Houck <tyronehouck at gmail.com> wrote:

> 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
>>
>> --
>>
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