[RE-wrenches] Strange battery overvoltage issue (Midnite AIO / Lithionics Battery)
Ray Walters
ray at solarray.com
Mon Jan 26 10:32:30 PST 2026
No, and the settings on the side of the battery did not include
recommended absorption time. I like the "cheat sheets" provided by
Fortress and Simpliphi for use with their batteries with various brands
of controllers and inverters. However, I've since started adjusting
those substantially for off grid. I found for Fortress for instance,
that the generator needed to be started at a higher voltage than
recommended, and I set the charge voltage on the inverters lower,
because the generator was running all day trying to fully charge the
batteries. Offgrid, the goal is to get the generator going before any
possible shutdowns, run the genny to get the batteries up to maybe 60%
or 70%, and then let solar take over again.
While open loop coms prevents some of the weird glitch shutdowns that
might happen with closed loop charging, using voltage controls with LFP
batteries is tricky, since the voltage is so stable until the bottom 20%
SOC of the battery. Below 20% SOC, the voltage seems to drop like a
stone, and triggering gen start and LVD is really dependent on the
loads. I'm still experiencing catastrophic battery shutdowns, that
require a trip out for manual reset, and/or dark start. I might get
usable settings for one combination (Victron: HomeGrid, ie.) but then I
need something different for Outback: Fortress combination......I don't
mind figuring this out (actually becoming an expert) but the drive times
are killing my bottom line (and my bottom).
Ray Walters
Remote Solar
On 1/25/2026 2:55 PM, Jay via RE-wrenches wrote:
> Did they offer up any reason why there are no charging or other
> programming specs online?
>
> Curious.
>
>
>
>
>
>
>
>> On Jan 25, 2026, at 12:56 PM, Ray Walters via RE-wrenches
>> <re-wrenches at lists.re-wrenches.org> wrote:
>>
>>
>>
>> Its really hard to find charge settings for Midnite Powerflow, but
>> Midnite tech support told me the #s are printed on the side of the
>> battery. Definitely not 57.6v, which sounds way too high.
>>
>> Charge : 56.16 vdc
>> Float: 54 vdc
>>
>> On 1/25/2026 11:20 AM, William Bryce via RE-wrenches wrote:
>>> This is more of a programming / battery issue than an inverter
>>> inverter. In looking at the system settings, you are pushing the
>>> voltages of LFP to the max. This will cause the BMS to protect the
>>> battery. The "Spikes are caused by the BMS operation not the
>>> inverter (the current has to go someplace), the BMS FET's open under
>>> load the voltage will spike. The BMS should be the last resort in
>>> regards to battery charging protection.
>>>
>>> All LFP batteries (cells) are mostly the same, and are made by 5
>>> companies. The upper and lower voltages are set for LFP cell makers.
>>> The battery (pack) builders then program the BMS, and post on
>>> specification sheets the recommended setting voltages. With _lower
>>> quality cells and lower warranties_, you will see the voltages are
>>> set _higher._ When using A+ cells and long warranties you will
>>> see_lower_ top voltage settings.
>>>
>>> Here are the recommended voltages for a 48V LFP (16S) pack when
>>> using A+ cells from CATL, BYD, and EVE (this is from the cell
>>> manufacturers recommendations)
>>> *
>>> *
>>> *Charging range:**~52 V to 56 V*
>>>#
>>>
>>> *Full resting:**~54.6 V*
>>>
>>>#
>>>
>>> *Nominal operation:**~51–53 V*
>>>
>>>#
>>>
>>> *Stop discharging (resting):**~48 V*
>>>
>>> *Recommended MAX voltage is 56.8V (for normal use) 58.2 **Absolute
>>> MAX (chemistry limit) Cell damage*
>>>
>>> You need to update the MNP AIO system firmware to V7. It is now the
>>> only AIO that has true charging control for LA (that works) the
>>> changes made were recommended by a highly qualified LA battery rep
>>> who is also a part of this list. Set the absorb setting as you
>>> need, but be aware that it does not start the adsorb until the
>>> current drops below ~ 10 amps or so.
>>>
>>> On Sun, Jan 25, 2026 at 12:48 PM Zeke Yewdall via RE-wrenches
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> I see on the Lithionics spec sheet it says a charged voltage of
>>> 57.6 volts This seems very high for a 16 cell LFP battery. I
>>> am used to using 55 to 56 volts, maybe 56.5 volts at most on a
>>> 16 cell LFP. I suspect that the 57.6 is the protection voltage
>>> of the BMS, not the appropriate absorb voltage setting. I have
>>> seen this error a lot on lithium battery spec sheets, where they
>>> give the overvoltage protection level, which is not an
>>> appropriate absorb setting for typical solar equipment.
>>>
>>> Not everyone will agree with me, but the way I set up absorb
>>> voltages when doing open loop lithium battery systems is to
>>> NEVER let the BMS do anything. if the BMS shuts off charging,
>>> that means that I already failed... the charge controller or
>>> inverter should have stopped charging before the BMS feels the
>>> need to protect the cells. Same with low voltage disconnect...
>>> if the BMS shuts off due to low voltage, I already failed -- I
>>> should have shut the load off before the BMS felt the need to
>>> turn of discharge to protect the cells. The BMS is like an
>>> airbag...only to react in cases of emergency when the rest of
>>> the system doesn't work properly.
>>>
>>> Open loop equipment (all of the traditional
>>> outback/magnum/schneider, etc stuff, plus any AIO's in open loop
>>> setup) is designed to always have a battery in the system to
>>> stabilize the DC bus voltage. Without the stabilizing effect of
>>> the battery, voltage spikes can occur. I find that many charge
>>> controllers, especially the midnite classic and victron ones,
>>> can actually keep the system fairly stable without batteries,
>>> but charging from inverters is more questionable, and especially
>>> charging from any DC generators can cause severe spikes if the
>>> battery disconnects. I have fried equipment when a lithium
>>> battery disconnected from a large kohler DC generator and the
>>> generator couldn't react fast enough to keep it from spiking to
>>> 75 volts or more. This is why you never want the BMS to
>>> disconnect... which means setting absorb at a level where the
>>> BMS never feels threatened. Lithium battery manufactures giving
>>> the voltage at which the BMS disconnects as the "charge to"
>>> voltage does not help the situation. That may work when
>>> charging it with a dedicated lithium battery charger, without
>>> anything else connected to the battery while it's charging. But
>>> in a functioning solar system with charging from multiple
>>> sources and loads all occurring at the same time, we need to be
>>> smarter than the battery, IMO.
>>>
>>> Zeke
>>>
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