question

larsea-dk avatar image
larsea-dk asked

Voltage drop after charge with light load

Hi all

I have 2mppts 250/100 with a 7.2kwp pv. Attached to a 16kWh diy lifepo4 battery and 2pcs MPII 48/5000(L1&L2), controlled by raspberry pi. Running ESS mode and max battery voltage set to 3.46v * 18cells = 62.2v

I have experienced than when my mppts stops charging at evening, the system voltage drops a lot eventhough no significant power load is drawn from the battery.

What could be the reason? Is seems to be after installing the extra MPII 48/5000 on L2 on my 3phase house.

Here are some graphs, which might be useful.

Thank you in advance.

img-8425.jpeg

img-8427.jpeg

img-8426.jpeg

Multiplus-IIESSvoltage drop
img-8425.jpeg (124.7 KiB)
img-8427.jpeg (158.0 KiB)
img-8426.jpeg (99.5 KiB)
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1 Answer
klim8skeptic avatar image
klim8skeptic answered ·

@larsea-dk Your plot looks normal for a lightly loaded (2 x multi not doing much) battery.

At dusk your cells are at 3.3v. At dawn the cells dropped to 3.27v. Normal.

It would be interesting to see the Soc and battery current for the same period.

Compare to my yellow celled battery, you can do the maths.

4-series-300ah.png



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