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

Mon Jan 26 10:01:44 PST 2026

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
> *maverick at mavericksolar.com
> 512-460-9825
>
>> On Jan 25, 2026, at 3:48 PM, Jason Szumlanski via RE-wrenches 
>> <re-wrenches at lists.re-wrenches.org> 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 
>> <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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