question

maxime-im-nomade avatar image
maxime-im-nomade asked

MPPT overload 14.5V

Hello everyone.

I'm the owner of a MPPT 75/30, who was working really fine for 2 years. I have Lithium battery 100AMP connected to the MPPT and a solar panel 200W in 12V.

Battery : 100AMP Lithium

MPTT : 75/30

Solar panel : 200Watts

Settings : Absorption : 14.5 - Float : 13.3


Here my problem : When the batterie start to be full, and I'm going in absorption mode, the voltage sometime rise to 15V or even 16V! I have notice it first by checking historic and after...


I arrive to track it to live. The solar panel was in absorption with 0 watts, and out of nowhere, surge to 90watts, and voltage switch to 14.4 to 15.5 for example.

Notice that this situation happened without using any device in the same time.

Do you have an idear if it's normal or not and how can I fixe it?


whatsapp-image-2023-06-03-a-135309.jpg


MPPT ControllersLithium Batterymppt overvoltage
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4 Answers
mvas avatar image
mvas answered ·

Did periodic Equalize mode get enabled? Maybe, if it appears off, turn it on and the turn off, to verify it is off. Have you tried a total power down of the Charge Controller?



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maxime-im-nomade avatar image maxime-im-nomade commented ·
Hello there, thanks a lot for your answer first of all.
  • For Equalize mode, I just did it now, we will see if it fix it or not...
  • Yes, actually, a couple of time to try to reset it, but it's doesn't fix it!

Thanks a lot !


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seb71 avatar image
seb71 answered ·

Does your battery have a BMS?

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It would help to clarify this if you could measure or monitor the voltages of individual cells.

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Your setting of 14.5V for absorption voltage is too high for a 4 cell LiFePO4 battery. This might be the cause (but not necessarily).

Assuming perfectly matched and balanced cells, 14.5V battery voltage would mean 3.625V cell voltage.

With LiFePO4 you should never go above 3.6V cell voltage (and never under 3.0V).

If you take a look at the charging curve of LiFePO4, you will see that when closing to fully charged, the cell voltage rapidly rises. In that stage it takes very little charging (very little energy) for a relatively big voltage increase.


So try lowering the absorption voltage to 14V and see if you still get the voltage spike. If all OK, then try 14.2V.

-------

Set Float voltage to 13.4V.

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Alexandra avatar image Alexandra ♦ commented ·

@Maxime Im Nomade

It definitely sounds like the bms is shutting down (not taking the charge) and the power overshoot causes a voltage spike that the mppt is reading.

A lithium battery not taking charge at higher voltages suggests battrry is going into protection, so likely cell overshoot/imbalance as @Seb71has mentioned.

Are you certain you have a lithium profile installed for the battery?

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maxime-im-nomade avatar image maxime-im-nomade commented ·
Hello Seb71, thanks a lot for your support and taking the time. Here my answer, as clear as possible
  • My batterie have a BMS, but basic one, so I can't take any data out of it
  • For absorption voltage, I have refer to the notice of the battery to be honest. I was also a little bit surprise, but I followed instructions.
  • I also think that the BMS is shutting down, and then it's creating the rise, but for sur it's not good that's it's happening

So, what I've done now :

  • Go to 14V for absorption
  • Float : 13,4V
  • I have reset the Battery preset for Lithium as @Alexandra suggest it. But I'm sure that something I have done before...

Full sun this week, so it's will be perfect for some tests !

Again thanks a lot for all of you :)


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nickdb avatar image
nickdb answered ·

And hopefully temperature compensation is disabled, but make sure you have selected lithium charging on the mppt.

Maybe send a screenshot of the battery section setup on the charger.

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maxime-im-nomade avatar image maxime-im-nomade commented ·
Hello @nickdb , thanks for your help.

This option is off I don't know what is for so ...


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maxime-im-nomade avatar image
maxime-im-nomade answered ·

whatsapp-image-2023-06-05-a-071557.jpgHere some screenshots for my actual settings whatsapp-image-2023-06-05-a-0715571.jpgwhatsapp-image-2023-06-05-a-071557e.jpg



whatsapp-image-2023-06-05-a-071557.jpg (68.9 KiB)
whatsapp-image-2023-06-05-a-071557e.jpg (68.0 KiB)
whatsapp-image-2023-06-05-a-0715571.jpg (66.3 KiB)
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