[RE-wrenches] Midnite AIO Generator Functionality

Mon May 12 15:57:54 PDT 2025

With the AIO, there are a few different basic settings that affect the
charging scenario for using a generator to charge the batteries: The Gen
start and stop relay (simple open and closed dry contact) and the battery
charging parameter (which determines what SOC the AIO will charge the
batteries to).  It wasn't intuitive for me at first, but now that I'm used
to it, it's not complicated.

   - If I'm using the AIO to start the generator I set the battery charging
   to start at whatever SOC the client wants to let the batteries discharge to
   before the gen kicks in, typically somewhere between 25% and 35% (depending
   on battery capacity, time of year, size of array, size of loads, etc).
   There is an AGS off  setting, which I might set at anywhere from 45% to
   85%, again depending on site factors. If the battery charging parameter is
   set lower than the ending AGS setting, the generator will continue to run
   and only carry the loads, but not charge the batteries - obviously not a
   recommended scenario.
   - If the client is manually starting and stopping the generator, then I
   set the AGS start at as high as it will go (90%) and stop at 100%, but
   disengage the remote genstart signal either at the generator or with an
   interrupting switch in the control wires. Otherwise if the SOC is higher
   the the gen start setting when the generator is manually turned on, the AIO
   will only use the generator to carry the loads, and again, not charge the
   batteries.  There is a "force charge" setting which tells the AIO to charge
   the batteries if AC is present regardless of the other settings, but I
   believe this setting drops back to off when the charging stops, so the 90%
   gen start setting is more reliable for manual gen starting.  If the client
   is bouncing back and forth between auto starting and manual starting, they
   need to understand the limitations of the programming.  I have implored
   Midnite to change the "Dry force" parameter (which start the generator
   through the AIO manually) to a gen control parameter, with an "Off, Auto,
   On" option, which would override the battery charge setting in the "On"
   position, forcing a charge when this option is used.

As far as solar charging goes when the inverter goes to standby if the
battery SOC drops below the "Discharge To (%)" (which I usually set to at
least 10% if not higher, again depending on the site specific
circumstances), in my experience the AIO continues to use the solar to
charge the batteries when available as long as the batteries haven't gone
dark and shut the inverter off. The client will need to put the inverter
from standby to "On' once the batteries have come back up to the minimum
battery SOC setting. I also believe if the batteries haven't shut down, if
the generator is started, the AIO will charge the batteries if the inverter
is turned back on, although I don't swear to this.

Howie

Sun Catcher
Howie Michaelson

On Mon, May 12, 2025 at 5:25 PM Dave Tedeyan via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Jason,
> Cant you just make the AGS turn on the generator before the inverter gets
> to the LBCO? Maybe this is more difficult if you do not have closed loop
> comms and the SOC drifts. I am just working through my first Midnite AIO
> setup now, so I cannot speak to the nuances of how it will work with that
> yet.
> Cheers,
> Dave
>
> On Mon, May 12, 2025 at 4:01 PM Ray Walters via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> That has not been my experience.  I have had to manually reboot Solark
>> systems numerous time off grid.  If there is snow on the array or otherwise
>> low PV output for a few days, the no load draw of the BMS then takes the
>> battery voltage low enough to shut the battery off.   This would be a
>> different situation with a knowledgeable owner onsite full time, but for
>> vacation properties, it will go into complete shut down, not coming back.
>>
>> Which gets into the manual and tech support for Solark:  its really not
>> clear what the different settings do, and how they interact.  I'm sure
>> there are engineers that know, but they aren't at Tech support. At least
>> you can change the programming on the touch screen, and you don't have to
>> get a quirky app up off grid to do basic changes.
>>
>> BTW, what happens when the developers quit keeping the App updated, 10
>> years from now, and you can't access the programming?  Planned
>> Obsolescence?  That 33 yr old Trace Inverter is still doing its job.....
>>
>> Ray Walters
>> Remote Solar
>>
>>
>>
>> On 5/12/2025 11:33 AM, MDElectricSolar via RE-wrenches wrote:
>>
>> We have been using the Solark inverter for GTBB and off grid clients. In
>> the case of low battery cut out the solar does stay alive in the background
>> and will recharge the batteries when the sun comes out the next day and
>> turn itself back on and provide AC power output.
>>
>> Michael D Nelson
>> MD Electric & Solar, Inc.
>> 707-684-0064 mobile
>> 707-884-1862 office
>> www.mdelectricsolar.com
>> www.facebook.com/mdelectricandsolar
>>
>>
>> On May 12, 2025, at 10:13 AM, Ray Walters via RE-wrenches
>> <re-wrenches at lists.re-wrenches.org> <re-wrenches at lists.re-wrenches.org>
>> wrote:
>>
>> 
>>
>> So the bypass switch gets the house power on, and I too always recommend
>> a hard bypass switch. However, you still need a 48 v power supply to get
>> the battery system back up, and that's becoming a serious pain in my aging
>> backside.  Until AIOs with Li+ batteries, lead acid would have enough
>> voltage to get the charge controller to come back on, and eventually the
>> customer could get the inverter back on too.  No special trip out.
>>
>> We need an independent circuit that would sense array voltage, and wake
>> up the battery, so it could take a charge: a backup battery for the offgrid
>> battery.  Without that, AIOs and Li+ batteries are not self healing like
>> Lead Acid.  We are going backwards fast, but with an amazing amount of new
>> Chinese technology driving the jalopy in reverse.  (Danger Will Robinson)
>>
>> Ray Walters
>> Remote Solar
>> On 5/12/2025 10:54 AM, Jason Szumlanski via RE-wrenches wrote:
>>
>> We always recommend a transfer switch to bypass the inverter and send
>> generator power to the loads. Most clients take us up on it. For retrofits,
>> sometimes there can be space limitations, however.
>>
>> As for the function of the AIO, there is no integrated mechanical bypass,
>> and since there is an internal relay controlling the generator input (or
>> smart load output on that breaker), I think the default function is for the
>> relay to open when the inverter turns off. AC voltage on the load side of
>> the breaker does not close the relay and turn the inverter back on
>> automatically.
>>
>>
>> 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 Mon, May 12, 2025 at 9:49 AM Dave Angelini Offgrid Solar via
>> RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
>>
>>> All sounds wrong to me. Call Midnite.
>>>
>>> Typically there is a AC bypass mechanical switch that allows the gen to
>>> bypass the inverter and power loads.
>>>
>>>
>>>
>>> *Dave Angelini Offgrid Solar
>>> "we go where powerlines don't"
>>>    <http://members.sti.net/offgridsolar/>https://offgridsolar1.com/ <https://offgridsolar1.com/>  <http://members.sti.net/offgridsolar/>
>>> e-mail  offgridsolar at sti.net <offgridsolar at sti.net>
>>> text 209 813 0060*
>>>
>>>
>>> On 2025-05-12 9:29 am, Jason Szumlanski via RE-wrenches wrote:
>>>
>>> Maybe I'm missing something, but it seems like there is a flaw in the
>>> logic for how generator integration works with this product. Unlike some of
>>> the other AIOs, you can't put the generator on the Grid input in an
>>> off-grid scenario. You have to use the Generator smart load breaker, which
>>> isn't a dedicated generator input, but a programmable circuit. This is
>>> problematic because it seemingly has a normally open internal relay that
>>> closes only when the inverter is ON. At least, that's how it seems to work
>>> in my limited experience.
>>>
>>> Why is this a problem? If the battery capacity drops below the low
>>> voltage cutoff, the inverter turns off. You have to turn the inverter ON
>>> for the generator relay to close so you can charge the battery, but since
>>> the battery is too low, the inverter won't turn on. You would have to
>>> reprogram the inverter to drop the cutoff voltage/SOC below the current
>>> battery state. For people who do not want to use AGS, or if AGS fails to
>>> start the generator for any reason, getting the generator to charge the
>>> battery manually is no easy task.
>>>
>>> Moreover, turning the generator on manually when the inverter is in an
>>> OFF state will not pass power to the loads, and will not turn the inverter
>>> ON automatically. You have to get the inverter turned ON somehow so that
>>> the generator power can pass through to the loads. And since the startup
>>> sequence for this inverter is very quirky, non-intuitive, and unreliable,
>>> that makes the problem even worse. I'm not sure if you can even turn the
>>> inverter ON when there is generator input and the battery is too low. I
>>> don't think you can because the relay is open and the inverter doesn't even
>>> see generator voltage when it is in an OFF state.
>>> This seems like a serious oversight and a reason to go with one of the
>>> other AIOs on the market. I believe the Sol-Ark 15K and EG4 18kPV will both
>>> immediately power loads and start charging when the generator is on,
>>> regardless of whether the generator is connected to the Grid or Generator
>>> input. Any AC input immediately passes through to the loads. This is
>>> because those inverters stay "on" when a low battery condition is met, and
>>> they simply stop using the battery to invert power if the battery
>>> conditions do not allow it, based on the settings.
>>>
>>> The logic of the Midnite AIOs turning "off" when battery cutoff is met
>>> and opening the generator relay doesn't make sense to me. Am I wrong about
>>> how this works?
>>>
>>> Jason Szumlanski
>>> Principal Solar Designer
>>> Florida Solar Design Group
>>>
>>>
>>>
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