diy solar

diy solar

My solar panels are not fully charging, Low power on Epever Tracer4215BN 430 W solar / 280Ah LifePO4

missoo

New Member
Joined
Dec 1, 2020
Messages
73
Hi everybody,

I have two 215W solar panels in paralel (total of 430W).
In France it is 1:45 pm, it's really sunny not cloudy and I can read on the MT50 that I only have 141,5W ....

Also according to the main screen of the MT50, the battery is fully charged but I only have 13,8V and my BMS app says that I only have 147Ah remaning on my 280Ah LifePo4 battery. I have the feeling that maybe the charge controller is not allowing a highest charge.

Anybody has an idea where the problem is coming from ?

Here are the settings I am using on the mt 50 :
Battery type User
Batt. Ah 280Ah
Temp Comp. Coeff -3mv/degree C/2V
Rated voltage Auto
Over volt dis. 14,6V
Charge limit 14,4V
Over volt rec. 14,5V
Equal. Charge 14,1V
Boost charge 14,1V
Float charge 13,6 V
Boost rec. 13,3 V
Low volt rect. 12,8V
Under volt rect. 12,8V
Under volt warning 12V
Low volt disc 11,5V
Discharge limit 11,4V
Equalize time 0min
Boost time 15min
 

Attachments

  • IMG_20220730_132112.jpg
    IMG_20220730_132112.jpg
    84 KB · Views: 15
  • IMG_20220730_125102.jpg
    IMG_20220730_125102.jpg
    92 KB · Views: 15
The charge values have seem OK.

Its not clear what stage the charger is in, if its in float then the values seem correct. Do you get more solar power when there is signification load on the battery?

The screen shot you posted on the 20 July did not show the correct state of charge, with a voltage of 13.1 it should have displayed a SOC of around 40 to 50%

Has the battery capacity been set up in the BMS to 280 Ah?

Try a reset of capacity in the BMS,
via the app click on the 3 bars, top left,
then 'function settings',
then 'reset capacity'.
This will reset the capacity based on voltage, once the battery has cycled a few times the result should be better.

note that some versions of the BMS you have may randomly loose the correct SOC and report incorrect values.

Mike
 
Hi and thanks for your answer,

How do I know what stage the charger is in ?
Do you get more solar power when there is signification load on the battery?
I didn't check it up yet. I'll do it later.

Yes the BMS is setted up to 280Ah.
Indeed, I noticed on the screenshot of the 20th july that the remaining capacity was not true. But today, without reseting, it was showing 130Ah left so probably a more correct value.

But I am wondering why the MT50 is showing a picture of a fully charged battery when my BMS indicates 50 % capacity left with 13,7V ?
 
Did you reset the BMS state of charge as suggested?
Ignore any reading of SOC from the solar controller MT50, its inaccurate.
 
Hello,

This morning I did reset the capactiy as you suggested.
I am not sure it was a good idea because now I have 280Ah remaining batter but my cells indicates 3,3V each which I guess is 60% of charge ...

So now my solar panels are charging 0W unless I use loads.

I still have power cuts and I am wondering if it's not coming from one cell (cell number 2) that has some issues balancing.... (See pictures).
I did balanced the cells after assembling them.

Could it be dammaged when I bought it?..
I noticed that it couldn't balance while the battery is charging with solar panels. But once it's off it seems to return to normal...
 

Attachments

  • Screenshot_20220731-080349_xiaoxiang.png
    Screenshot_20220731-080349_xiaoxiang.png
    312.9 KB · Views: 18
  • Screenshot_20220731-080743_xiaoxiang.png
    Screenshot_20220731-080743_xiaoxiang.png
    313.8 KB · Views: 16
  • Screenshot_20220731-080912_xiaoxiang.png
    Screenshot_20220731-080912_xiaoxiang.png
    313.9 KB · Views: 12
  • Screenshot_20220731-082943_xiaoxiang.png
    Screenshot_20220731-082943_xiaoxiang.png
    313.6 KB · Views: 13
  • Screenshot_20220731-084135_xiaoxiang.png
    Screenshot_20220731-084135_xiaoxiang.png
    312.7 KB · Views: 14
  • Screenshot_20220731-090740_xiaoxiang.png
    Screenshot_20220731-090740_xiaoxiang.png
    314.5 KB · Views: 18
Cell 2 seems to have a problem. Check all connections, buss bars and BMS leads at cell 2 position.

To confirm cell 2 is the issue swop position in the battery with cell 1.

Mike
 
How can I be sure which one is number 2 and which one is number 3?...

Edit : I noticed one of the BMS cable was a bit untighten on the positive of cell 2 or 3. I tightened it and I hope tomorrow it will work better
 
Last edited:
How can I be sure which one is number 2 and which one is number 3?...

Edit : I noticed one of the BMS cable was a bit untighten on the positive of cell 2 or 3. I tightened it and I hope tomorrow it will work better
It will :).
 
Hello,

I am charging my battery right now.
Here is the cells balance.
Does the cell difference of 0,074V seem reasonable ?
 

Attachments

  • Screenshot_20220802-150706_xiaoxiang.png
    Screenshot_20220802-150706_xiaoxiang.png
    320.2 KB · Views: 18
Yes the cell difference is excessive
Hello,

I am charging my battery right now.
Here is the cells balance.
Does the cell difference of 0,074V seem reasonable ?
Yes that is excessive. It states that the cells are balancing so at what level of imbalance do you have your BMS configured to start balancing.
 
Hi,
The balanced turn-on voltage is set to 3,4V and the balancing precision is of 0,015v.

For the boost tome, somebody recomanding me that.

Is it allright these settings ?
 
Hi,
The balanced turn-on voltage is set to 3,4V and the balancing precision is of 0,015v.

For the boost tome, somebody recomanding me that.

Is it allright these settings ?
Settings seem ok but I have my differential set at 0.02v.

If your were charging when you posted that photo then why is the BMS allowing the battery to be charged if you have a differential of 0.074. You have indicated the balancing to commence at 3.4v but what are your cell settings to turn off charging if your cell voltage differential get excessive or is that what you mean by Balancing Precision.

Ay 13.8v your battery is fully charged so are you able to reset the SOC on your BMS as Mikefritz suggested. I am able to on my Daly BMS. The BMS SOC is only an approximate reading of the available capacity, if you want a more accurate reading then you will need to buy yourself a shunt.

My apologies for the delay in replying but Im travelling around the UK and will be in France in a couple of weeks. :)
 
If your were charging when you posted that photo then why is the BMS allowing the battery to be charged if you have a differential of 0.074.
I have no idea, I am not sure I get all of it.

I did reset the SOC of my BMS. And I also have a shunt. It didn't change anything.

It seems my cells have issues balancing when the battery is charging or discharging. See the pictures below.

Do you have any idea what could be wrong ?
Should I disassemble, reassemble all of it ?.. And balance all of it again ?..

Where are you travelling in France ? :)
 

Attachments

  • img1.png
    img1.png
    313.2 KB · Views: 14
  • img2.png
    img2.png
    312.7 KB · Views: 14
I have no idea, I am not sure I get all of it.

I did reset the SOC of my BMS. And I also have a shunt. It didn't change anything.

It seems my cells have issues balancing when the battery is charging or discharging. See the pictures below.

Do you have any idea what could be wrong ?
Should I disassemble, reassemble all of it ?.. And balance all of it again ?..

Where are you travelling in France ? :)
Ok firstly that one cell is way over and showing 3.951v. You need to discharge that cell quickly or you will destroy it If you haven’t already. Unless you have a means of discharging the one cell then you need to discharge your battery and get that cell below 3.65v.

Looking back through your posts you said your battery was at 13.8v. That is as fully charged as you need to be!. I will post a video to show you what I mean when i can.

You solar controller appears to be charging ok but your BMS is clearly not doing its job at protecting the cells from overcharging. I just looked through your photos and the BMS is showing ‘Protection none’ therefore I suspect that you have it turned off from protecting the cells somehow.

Yes discharge that cell. I would disassemble that pack and follow Will’s video on balancing then reassemble. Make sure that protection is turned on your BMS and when you connect back up to your solar be happy that you have reached 13.4 as per you photo that you last posted.

I’m travelling so may not be here for a day or two but I’m sure @mikefitz will help you if need be.

Over in France on Monday via the Tunnel and travelling to Calais, Reims, Colmar in the Alsace wine region, Chalons-en-Champagne, back to Calais and then a Ferry to Dover. I’m from the UK originally but live in Australia and every few years i come over and go to Le Mans with friends. :cool:
 
Hi again Missoo.

Firstly stop worrying about the SOC shown on the BMS for the moment and lets get your battery sorted. Even if the SOC is showing 50% when it is at 95% the BMS isn’t going to use the SOC to regulate the maximum level of discharge as it uses voltage to do that.

Here are a link to explain where your battery is at in relation to voltage.


When I can I will find a good video for you.
 
Missoo,

Here is a good video to explain a few things for you which are mostly in the second half of the video. To me Andy is a bit of a Rowen Atkinson of solar power. He is very funny and don't let his bumbling nature fool you as he gives himself away at times as being very intelligent.;)


:)
 
Hi Tim Tim,

Sorry I am also travelling. I am in Dordogne right now !

I thought I could charge my battery to 14,4V but maybe I can't reach this voltage because of cell 2 which is overcharged very quickly...

The weird thing is that cell 2 was going up to 3,9v while charging but when I stopped the charging it went back directly to 3,3 V...
It seems the BMS have issues balancing while charging... I will try to find out why I have "protection none".

How could I know if cell number 2 is dead ?

I would love to top balance it again but I don't have time and equipment right now...

Enjoy your trip !
 
Hi Missoo,

Enjoy your travels :cool:. I‘m in your beautiful country at the moment and presently at Colmar for 3 nights.

No, you should not be charging to 14.4 so set your maximum battery voltage on your BMS to 13.4v and cell voltage to 3.35v. until you are able to balance the pack again.

When you are stop charging, you will always see the voltage drop as the battery rests. The same happens when using and inverter and discharging a battery except you will see the voltage climb.

You need to stop overcharging cell number 2 so don’t let it go over 3.35v as you may of already damaged it. When you do a top balance again the cells should all sit at a very close voltage after resting for a few hours. If cell 2 is damaged then it will drop more than the others.

If you look back at the photo in your post dated 11 August with the battery at 13.4v then that is perfect. Have you discharged your battery to get cell 2 back down? You will need to ensure that you do not overcharge it again.

i just took a quick look at your BMS and it looks like you need to have that protection turned on. Hopefully someone may know how to do it.
 
Last edited:
you should not be charging to 14.4 so set your maximum battery voltage on your BMS to 13.4v and cell voltage to 3.35v.
I agree that the charge volts should be lowered but disagree with lowering the BMS values.

Keep the protection voltages at 3.65 for cell volts and 14.6 for battery volts.
To prevent over charge reduce the charger volts to 13.8 volts.
firstly that one cell is way over and showing 3.951v.
The screen grab showed, than when charging, the cell 2 went to a very high voltage, the BMS should not have allowed this.
The indication 'protection none' suggests the BMS did not detect the 3.95 volts, what are the BMS protection volts set to?
Re check the cell inter connections and BMS leads, 99% of the time unusual high volts when charging are down to this. Check all buss bar connections. If possible verify BMS reading with a meter direct on cell terminals.
Note that the BMS can be configured for different types of lithium cells, ( with different protection values), make sure yours is configured correctly.

weird thing is that cell 2 was going up to 3,9v while charging but when I stopped the charging it went back directly to 3,3 V...
unbalanced cells or faults in the interconnections only show up when under charge. With cell imbalance the voltage rise will only occur when the cell is almost full, the 'weak' cell need only have a fraction less capacity than the others for this to happen.
If there is a connection issue, corrosion on contact areas, not enough contact pressure (example, fixing is bottoming out), then under charging the resistance will increase the measured volts between cells.
I could charge my battery to 14,4V
your battery (with balanced cells) will be charged at 13.8 volts, there is no need to aim for 14.4 volts
Consider each cell is charged for practical use if it reaches 3.4 volts under charge.
LFP charge.jpg
Mike
 
Back
Top