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derbaertigefrytz avatar image
derbaertigefrytz asked

MPPT 75/15 does not load my LiFePo4

Hello.
I shortly bought an MPPT 75/15, a LiFePo4 12V/100Ah and a Wattstunde 200W Solarkoffer.

I used the cables set that was delivered with my Solar Panel and I believe, they are sufficient for the job.

The battery had a voltage of 13.48V when I connected it. So I thought it was not really empty.

The VictronConnect App shows a solar input of 60-147 Watts.

I expected to see a charge voltage of 14.2V. I expected the charge voltage to be constant.

However the battery stays in bulk mode with voltage between 13.17 - 13.63 V depending on actual solar input. Battery current is up to 7.5A

I also expected the bulk mode to end after some hours, (after a harvest of near to 500Wh in the last two days), as the battery was not empty.

What am I missing?


Thanks for your support

Frytz


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3 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Vom Namen und Schreibstil (laden im sinne von aufladen ist im englischen "charge" nicht "load") her nehme ich an sie sind Deutscher oder zumindest aus dem deutschsprachigen Raum.

Ich würde einfach sagen, die Batterie ist noch nicht voll.
Im Auslieferungszustand haben Lithiumakkus meist so 30-40%.
d.h. 60-70Ah "fehlen" was etwa 800-900Wh entspricht. Also einfach erst mal ohne Verbraucher weiter laden lassen, dann werden die 14.2V irgendwann erreicht.

Was ist es denn für eine Batterie?

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derbaertigefrytz avatar image derbaertigefrytz commented ·

Erwischt. Mein Englisch war mal besser.
Danke.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ derbaertigefrytz commented ·

Kein Problem. :)

Bei Lithiumakkus ist es nicht so einfach einem Spannungswert einen Ladezustand zuzuordnen. So etwa zwischen 10-90% SOC ändert sich die Spannung nur um wenige hundert mV. Unter 10% sackt sie sehr schnell ab und über 90% steigt sie dann recht schnell an.
https://de.wikipedia.org/wiki/Lithium-Eisenphosphat-Akkumulator

Daher weiterhin meine Vermutung, das der Akku einfach noch nicht voll ist, solange die 14,2V nicht erreicht wurden.

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Rob Fijn avatar image
Rob Fijn answered ·

Hello, did you tell the MPPT 75/15 that the battery connected is a Lithium battery ? This must be done.

Rob


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derbaertigefrytz avatar image
derbaertigefrytz answered ·

Hello Sirs

Thank you for your answers.

The battery is a , I would say, Noname, a Xenes Eco Line. The manual says 80% discharge is at 11.5V and end of charge is 14.6V.
Therefore, I thought 13.48V should be at least more then 50% charged.

In Settings - Battery, I selected the defaults for "Lithium Iron Phosphate", that were shipped with the app, which seem to match the requirements of my battery.

Best regards

Frytz

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