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
<[email protected]> 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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