[RE-wrenches] Strange battery overvoltage issue (Midnite AIO / Lithionics Battery)

Sun Jan 25 11:54:24 PST 2026

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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