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

Mon Jan 26 09:19:56 PST 2026

Maverick

That is a really good chart!

Thanks for providing that.

On Mon, Jan 26, 2026 at 11:53 AM Maverick Brown via RE-wrenches <
re-wrenches at lists.re-wrenches.org> 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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>> <51V110A-8D-MODULE-REV2 (1).pdf><Screenshot_20260125_155512_Chrome.jpg>
> <Screenshot_20260125_155550_Chrome.jpg>
> <Screenshot_20260125_155623_Chrome.jpg>
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