We're not the only ones wondering about best settings for LFPs. I've
noticed over the years both Simpliphi and Fortress have changed their
recommended charge settings substantially. Fortress seems to have gone
to a higher voltage and very low absorb time. Considering they're
roughly the same cells inside on all of these, I find the variations in
settings interesting.
Beware, some batteries like the Simpliphi will literally let the smoke
out if they go over 60 v. I was excited about the 15 cell (48 v
nominal) HomeGrid batteries, since they would be closer to lead acid
voltages. However, we ended up having quite a bit of firmware troubles,
and the "outdoor" enclosure and heating left a lot to be desired.
Like William, I don't consider myself quite an expert on LFP, but I've
done systems with Blue Planet, LiFe Blue, Simpliphi, Fortress, Homegrid,
and Midnite. Even though I had a hard time finding charge settings, the
Midnite Powerflo 16 has been my favorite so far. I just did a system
with a Rosie and a pair of Powerflo s. Every possible load on in the
house, then kicked the well pump, and it didn't even blink the LED lights.
Ray Walters
Remote Solar
On 1/26/2026 9:51 AM, Maverick Brown via RE-wrenches wrote:
I have never believed any LFP battery maker that has 58.4V for charge
voltage. That’s 3.65 Volts per cell in a 16S configuration. If you
have any cell imbalance inside the pack, one cell could go above the
upper limit of 3.65Vpc.
I have installed serval brands of LFP batteries, some great brands and
some not as great.
In pretty much all cases, I used 3.45Vpc (55.2V) as the Absorb and
then set other voltages as appropriate based on that. In several
cases, I also enabled EQ and set it to 3.5Vpc (56) just to make sure
that cell balancing has a chance. If the voltage is too low, you will
see a wider battery to battery SOC spread. I have corrected that by
increasing the Absorb time and/or bump up the ABS Voltage.
Many battery companies have been integration guides for their battery
to Outback or Scheider. I have digested this to see what the ranges
are for open charging. It would be good to get more details about:
Cell balancing activation voltage
Method for reading the cell voltages internal to batteries (a few
companies have simple cables and easy apps for such, Pytes and Fortress)
Method for reading individual battery SOC (Pytes has a serial cable
and an app; Fortress has Guardian comm box, and there are others)
It would be good for long term health and understanding for wrenches
to have more information…
Here is my current working document on charging open loop. Let me know
what you would do differently. Any suggestions are appreciated. I will
send the XLS version to anyone who wants it.
Maverick Brown
Off-Grid Solar Commander since 2006
*Maverick Solar Enterprises, Inc.*
* • Solar Commander Remote Power*
* • SunFlow Systems Cathodic Protection
*[email protected]
512-460-9825
On Jan 25, 2026, at 3:48 PM, Jason Szumlanski via RE-wrenches
<[email protected]> wrote:
The specs for this particular battery list a charging voltage up to
58.4V. I believe the BMS protection level is set at 60V, but I need
to confirm with the manufacturer when they open on Monday.
I just noticed that the AIOs responded to a relatively high load and
entered a re-bulk type of behavior. But the voltage stayed withing an
acceptable range. I'm not clear on how the AIO handles re-bulk and
also why the float voltage setpoint isn't being respected (or how
absorb time is determined).
Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208
On Sun, Jan 25, 2026, 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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