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
<[email protected]> 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
<[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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