[RE-wrenches] Midnite AIO Battery Low/Lost Behavior

[Howie Michaelson]

Kirk, if the batteries are in closed loop, the SOC is being reported by the
battery BMS. In open loop, my understanding is the SOC is usually less
accurate as it is calculated by the inverter based on our programming
settings.
The SOC calculation in closed loop is based on much more data  (collected
by the BMS), but also depends on the level of sophistication of that
firmware. The assumed SOC can get significantly out of whack with the
actual, especially if they are top balanced with some regularity.  What
that frequency of required top balancing varies from product to product.
The inverter calculated SOC (open loop) is generally less accurate and
probably requires more regular top balancing than closed loop, to remain
within a reasonable estimate of the actual SOC.
Howie

On Tue, Jul 15, 2025, 9:24 PM Kirk Herander via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Generally speaking, with these respective AIO inverters, where is the
> supposed SOC being calculated from and how often is that source manually or
> auto calibrated?
>
> I only have experience in AIOs with Fortress inverters and their evault
> batteries. I had a situation where the house went dark when closed-loop SOC
> read 35%.
>
> Some may remember from this forum, Fortress confirmed battery volts had to
> go above 55v to auto recalibrate. It was a Vermont mid-winter and the
> customer never turned on the genny because he thought the bats were safely
> at 35%., Actually they were close to 0% due to the lack of winter
> recalibration.
>
> On Tue, Jul 15, 2025 at 8:56 PM Lou Russo via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> We definitely experience that. Mostly with Sol-Ark and Homegrid.
>> Generator even starts but it is not quick enough to do anything. Have
>> the client power cycle and everything is fine. Had this happen last week,
>> batteries were at 79%.
>>
>> Aloha,
>> Lou Russo
>> Spree Solar Systems LLC
>> C-34322
>>
>>
>>
>> On Tue, Jul 15, 2025 at 1:44 PM Howie Michaelson via RE-wrenches <
>> re-wrenches at lists.re-wrenches.org> wrote:
>>
>>> These are useful suggestions for how to deal with low battery
>>> conditions, however I understand Jason's situation to be a hardware or
>>> firmware issue - the inverter temporarily reads battery voltage or SOC as
>>> 0% and shuts off, needing manual intervention to turn back on.  I'm not
>>> sure if i am having the same issue on at least a couple of sites with an
>>> AIO and 1 or 2 PF16s in closed loop, by I've seen the inverters without
>>> warning seemingly loose the batteries (which are in a relatively high SOC
>>> - 70-80%), see no SOC, then shut itself off.  So far the client has gotten
>>> the inverter back to on by shutting it down entirely and restarting it.  It
>>> fires back up and operates fine as though nothing has happened.  Anyone
>>> else experiencing that?
>>> Howie
>>> Sun Catcher
>>>
>>>
>
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