MPPT remains in float

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markusg asked Jun 28, '21

MPPT remains in float

Hello,

I've two Smart Solar MPPT 10/75, which are connected to a Life4po battery with builtin bms. A compressor fridge is connected to the battery. Normally everything works fine. But when it's a warm, the battery bms seems to stop charging. I'm in discussion with the battery manufacturer because of this.

When the battery stops charging the MPPT change to float state. This seems to be okay and it's understandable for me. But I don't understand, why it remains in float state, even when the fridge starts and drains the battery? Only in the evening, the MPPT change back to bulk state.

Do you've any idea, why the mppt remains in float and how could I fix it?

Thank you!

Markus
Screenshot_20210628_141731.png mppt_config1.jpeg mppt_config2.jpeg

MPPT Controllers float

screenshot-20210628-141731.png (171.9 KiB)

mppt-config1.jpeg (67.6 KiB)

mppt-config2.jpeg (79.1 KiB)

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Answer 1 · 2021-07-01T11:30:48Z

Alexandra answered · Jul 01, 2021 at 11:30 AM

@MarkusG

I can see your pv voltage is hovering barely over the 5v for the mppt to start up and charge. So my first suspicion is insufficient pv.

I can see your battery voltage does not reach the set voltage for bulk charging at 14.4v in any case which confirms insufficient pv voltage. Since now the battery voltage has risen and now the 5v gap is closed.

Try adding a panel or if you do have two series connect them for a higher string voltage.

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Answer 2 · 2021-07-01T13:18:34Z

solardude answered · Jul 01, 2021 at 01:18 PM

Try setting your absorption at 14.0V. Most BMS will disconnect from MPPT if any cell goes above 3.65V. When charging to 14.4V you will have one cell that charges faster and will be above 3.65V.

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