[RE-wrenches] AGS quiet time

[Chris Sparadeo]

Another nice-to-have feature would be Gen stop based on PV production.
Customers dislike hearing  their generator run to finish a charge cycle in
the am when the sun is out.

On Sat, Apr 11, 2026 at 1:01 PM Jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> My thoughts exactly
>
> On Apr 11, 2026, at 9:35 AM, Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
>
> You're making the case for multiple AGS start setpoints. There should be a
> quiet time override SOC for AGS.
>
>
> Jason Szumlanski
> Principal Solar Designer | Florida Solar Design Group
> NABCEP Certified Solar Professional (PVIP)
> Florida State Certified Solar Contractor CVC56956
> Florida Certified Electrical Contractor EC13013208
>
>
>
>
> On Sat, Apr 11, 2026 at 9:10 AM Zeke Yewdall via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> A recent thread included Quiet Time in the list of non-included features
>> with newer inverters.  And I too have had customers asking for this. But,
>> in many cases, I find that quiet time is not actually a useable feature for
>> many current off grid houses with lithium batteries, and this is why.
>>
>> With lead acid battery banks, we typically designed for the generator to
>> start around 50% SOC.  But, occasionally we could discharge down to 20% SOC
>> without damaging the batteries long term.  And, typical off grid houses
>> were usually designed with fewer nighttime loads, compared to nowadays.
>>  So, if the battery bank hit 50% SOC at 9pm, but quiet times extended till
>> 8am, we still usually had plenty of reserve left to wait till 8am before
>> starting the generator without any additional failures or battery damage.
>>
>> But a lot of current off grid systems with lithium batteries are sizing
>> for a lower days of autonomy (because of the higher cost of lithium
>> batteries, though that's changing now), and deeper regular depth of
>> discharges.  Generator start is often set at 20 or 30% SOC instead of 50%.
>> If we are planning for regularly discharging below 50% SOC overnight, which
>> I do commonly see, there's not nearly so much reserve capacity to wait for
>> a generator start.  If we hit 20% SOC at 9pm, with a smaller battery bank
>> relative to the load, and a higher nighttime load from more things
>> remaining on all night that we never used to have (routers, internet,
>> heating system controls/pumps/etc), then the chances of us making it till
>> 8am to wait for the generator start is a lot lower -- we risk a BMS
>> shutdown of the battery sometimes betwen 0% and 10%, before 8am, which
>> depending on the particular equipment can be a difficult situation to
>> recover from.  Many AIO's will only black start batteries from solar, not
>> generator, and most (though not all) older charge controllers and inverters
>> will not black start batteries from either solar or generator.
>>
>> So, because we are using deeper discharges, using more energy overnight,
>> and waiting longer before a SOC based generator start, we often don't have
>> the option of waiting 4 or 8 hours or such to start the generator.  It
>> needs to start very soon after the call for it, or we run into further
>> problems.
>>
>> What would be ideal is a system that looks at SOC before quite times
>> would start, and if it's not sufficient to make it through a typical night
>> because it's been a cloudy day, starts and runs the generator a bit before
>> quite times start, rather than hoping to make it to morning before running
>> it.  An experienced off grid owner can do this automatically, topping the
>> batteries off before going into the night if they are too low.  But
>> unexperienced owners or ones who just don't watch their battery SOC all the
>> time, will not.  Perhaps we'll come up with AI driving controls that watch
>> the typical batery use patterns and look at the weather forecast, and can
>> do this, just like the experienced off grid operator does.
>>
>> Zeke
>>
>>
>> --
>> Zeke Yewdall
>> PV Engineer
>> NABCEP #031508-89
>> zeke at darkforestsolar.com
>> 303-523-3592
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