help with single cell overvoltage and BMS overvoltage at 100% capacity

[MichaelPlace]

I’m posting to ask why my BMS overvoltage and single cell overvoltage continue to keep going off.
So to start, my family and I just moved off grid to build a house in the Ozark of Arkansas. We are currently living in a Fifth wheel trying to get everything situated before we begin our build.

Set up: I have 3 295 watt solar panels connect to a 80amp MPPT Epever tracer controller. I’m running a 120ah Nithin 3.6V converted into a 24V system with an 100AH Overkill BMS on the battery. Then my inverter is a 2000/4000 Giandel Pure Sine inverter. I’ve got my control parameter settings at
100AH on the controller
Over charge Disc. At 31.0V
Charge limit at 29.0V
Over charge Rec. at 29.4V
Equal charge at 29.0v
Boost charge 29.0v
Float charge 27.6v
Boost eec. At 26.4v
Low volt. Rect. 25.6v
Under volt rect at 24.5v
Under volt warn 23.0v
Low volt disc at 22.2v
Discharge limit 21.2v
Equalize time at 180min
Boost time at 120min

so every time my battery gets fully charged and left to float at a certain time after a while of it fluctuating between charge and discharge once at 100% the inverter begins to get set off to say OV (over voltage) and triggers off my BMS to register either single cell overvoltage or BMS overvoltage I’m not sure if it’s the settings I’ve chosen or what I can do to trust leaving this system alone for the day while at work any wisdom would help greatly.

here are some pictures and also the inverter is plugged in to a 30amp extension to a 50amp fifth wheel

 

[Bud Martin]

So just ONE CELL has Voltage that goes too high and trip the BMS?
How high of the Voltage on that one cell goes up to?
I would verify the connection on that cell, and you can also move the cell to another position to see if the problem follows to the new location or not.

 

[Gazoo]

I’m posting to ask why my BMS overvoltage and single cell overvoltage continue to keep going off.

Did you parallel top balance those cells?

 

[time2roll]

I would reduce your basic charging voltages to be closer to 28.0 to 28.4 with float closer to 26.8 volts.
Some other settings may need to go lower to fit right.

Give it a few days like this and see where it goes.

Basically you are charging very close to the top max and you are seeing the BMS going into protect mode. Should be able to run a bit lower for daily use and charging.

 

[MichaelPlace]

Thank you for the help. Do you think this also needs to be done on the BMS overkill program or just on the solar charge controller?

 

[OnTheRoadAgain]

Try adjusting just the Controller as T2Roll mentioned first.

You didn't post the BMS parameters so it's unknown but BMS sounds like it's working.

 

[MichaelPlace]

I’ve tried multiple times to reduce the charge limit but the mt50 I’m using continues to say para. Error for parameter error

 

[MichaelPlace]

I’ve tried multiple times to reduce the charge limit but the mt50 I’m using continues to say para. Error for parameter error

Is there something I’m doing in the configuring that is causing the solar charge controller not to drop below a certain OV disc. And charge limit?

 

[OnTheRoadAgain]

Did you post the parameters in your BMS ?

Everything properly set for 24v battery?

Maybe your inverter is causing the fault?

 

[MichaelPlace]

Did you post the parameters in your BMS ?

Everything properly set for 24v battery?

Maybe your inverter is causing the fault?

I’ll be honest I’m a serious beginner at all of this. I’ve not touched my BMS parameter because I’ve been told that you could easily really mess up the batteries. But this is the current read of the parameters of the batteries now

 

[MichaelPlace]

Thank you guys for the help it’s a huge!

 

[time2roll]

Is there something I’m doing in the configuring that is causing the solar charge controller not to drop below a certain OV disc. And charge limit?

I have read posts where changing the charge profile can be filled with errors and be a struggle on this controller.
Does it have any canned settings with lower voltage such as GEL?

 

[MichaelPlace]

I have read posts where changing the charge profile can be filled with errors and be a struggle on this controller.
Does it have any canned settings with lower

 

[MichaelPlace]

I’ve not tried it yet. The forums and videos I watched recommended user because supposedly this setting covered LifePo4 battery settings? So I can put it on Gel then and trying to configure the settings?

 

[time2roll]

GEL is a bit lower and should eliminate equalizing so it is sometimes what I suggest when there are limitations.
Read the specs and verify. Post a link to the manual if you are really stuck.

 

[MichaelPlace]

GEL is a bit lower and should eliminate equalizing so it is sometimes what I suggest when there are limitations.
Read the specs and verify. Post a link to the manual if you are really stuck.

I tried to put it on Gel and change the settings just to see and it wouldn’t allow for me to adjust any of the settings beside the boost time and the degrees plus what kind of battery I had (24v) other than that it wouldn’t let me manage any of the setting of what was preprogrammed

 

[MichaelPlace]

I tried to put it on Gel and change the settings just to see and it wouldn’t allow for me to adjust any of the settings beside the boost time and the degrees plus what kind of battery I had (24v) other than that it wouldn’t let me manage any of the setting of what was preprogrammed

The settings I had it on if you were going to follow it how would you adjust it. Is their something that won’t let me drop the over voltage disc. Any lower then From 30.1 or the charge limit any lower then 29.1 on some of the other settings?

 

[Diysolar123]

It sounds like the BMS is doing what it should do..

try and approach this by breaking your system into its primary parts; the inverter, charger, and the BMS..
if possible, disconnect the inverter and just focus on the BMS, charge controller, and battery; make sure that is all working correctly.

first setup your BMS so that it is properly setup for you battery type. This really is not that tough and its the final defense of your battery pack to protect them, so you want this working first.

pushing your battery cells to their limit of 3.65V/cell is just asking for trouble; you basically do this one time when you are make sure you have "balanced" your cells and never go that high again.

when starting out I would keep the "top" cell voltage around 3.4 or 3.45v/cell at most.
with that sorted out lets look at other BMS parameters that can now be set to nice safe numbers:
high voltage disconnect when something has gone wrong, normally you NEVER see this unless you batteries are well out of balance: 3.60V/cell or a pack voltage of 28.8V
low voltage disconnect will be 2.8V/cell which is 8*2.8=22.4volts
your BMS is the last line of defense, it should never be tripping any of these limits.

regarding charging...
use a good voltage meter and test each cell to see if they are reasonably balanced (within 10mv).
If they are NOT balanced, I would recommend a configurable balance charger such as the ISDT Q8 max which does a pretty good job of balance charging your cells. You could also tear down your pack and do a proper parallel top balance if you are a patient person.

We now move forward on the premise your cells are "reasonably" balanced and at LESS THAN 3.6V/cell...
If they are higher than that, well, just wait a day and they will settle down nicely to where we want them.
perform a simple DC load test to see how the battery and BMS work together...great time to break out your cheap 150W battery load tester hehe
The important part is to make sure you have a good battery/wire/bms combination before you get to the harder part.

Now we have your battery and BMS safely setup to do their job.

time to setup the charge controller!!
Your charging voltage will be a safe 3.45V/cell:
3.45 * 8 = 27.6VDC
float and bulk can both be set to 27.6VDC
make things simple and keep everything the same.
make sure there is NO equalizations or boosting going on; you should be using a customer USER profile to make sure that is all off.
If you cannot turn them off, well, set them all to the exact same 27.6V value.

battery overvoltage will be set to the same as the BMS which is 28.8V; this is a safe top end that you should never see unless something really is wrong.

plug in your battery and see if this play well together with a bit of just DC loading...no inverter yet.
if it is charging and discharging its time to put the inverter in the mix.

The inverter will have its LOW voltage disconnect set to 3V/cell or 3 * 8 = 24VDC

make sure all your balance leads are good, check for anything frayed or loose.
put a small AC load on the inverter and see how it does...
increase the load and watch if you suddenly see a suspect cell voltage sagging via your BMS app. This could be caused by a poor wire connector, loose connector, or even a bad cell...however, if you have already done your balance and load test you KNOW the battery itself is good.

 

[Tecnodave]

@Micheal Place,

I see your problem very clearly. Unless this is a very old EPSolar AN unit there are three battery types in the user menu.
1st is flooded lead acid
2nd is gel cell
3rd is user definable....

that is where you need to enter your settings in “ USER DEFINED BATTERY TYPE” flooded lead acid and gel cell are totally the wrong settings...way too high a voltage..set it at 27.6 for the bulk voltage and the absorb setting should be 27.6 and if it has a time setting for adsorb set that to 5 minutes, the float setting should be set at 24.0 volts so basically it will never go to float, lithium batteries do not need a smart 3 stage charger like lead acid does. the bulk setting should do all the work.

On the older units especially the ones branded EP Solar......not EP ever, there is very little adjusting that you can do, and they will not properly charge some battery types, including lithium and large format flooded batteries such as L-16

I got rid of my EP Solar charge controllers long ago so im not up to date on the current models.
I have heard of several persons having the issue that you are having, going to the user defined battery type has solved most issues

 

[Tecnodave]

@Michealplace

Your whole problem is on the Tracer you are in “Flooded Lead Acid” , wrong selection you need to be using, “USER DEFINED BATTERY TYPE”, select that setting then enter the sets for lithium, no equalization, boost or float settings are required for lithium batteries, just set the bulk charge to 27.6 volts, set boost for the minimum time that the controller will accept, maybe 3 minutes


I went back and peeked again at your photos and that is not one of the old tracers that are not very adjustable, it ”should“ have a user type or lithium setting, lithium batteries only need the bulk setting, all else is not needed and if you must enter a value keep it below the bulk and set the time to the minimum.