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oyster53 avatar image
oyster53 asked

SmartSolar MPPT Reads Higher Batt V than actual.

Newly installed:

  • 2 x 110W SunPower flexible panels in series. 15A in line fuse between + on panel and:
  • 100/20 - wired via negative on charger side of batt monitor shunt & positive (15A fuse) to batt terminal.
  • 4 x 200A Calcium Batts in series & parallel, recently fully drained. Now holding 70% charge, draining quickly.

Two battery monitors + meter will measure voltage at battery at 24.5v. App on SmartSolar reads Batt voltage at 27.9. So, charging does not get triggered. Any suggestions? Many thanks in advance.


battery charging
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klim8skeptic avatar image klim8skeptic ♦ commented ·

You have a 20a mppt, with a 15a fuse.

A good place to check.

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gbarnaud avatar image
gbarnaud answered ·

Hi Oyster53

Did you measure the actual voltage at the MPPT output ? Just to be sure that it is a VE problem or not.

Which wire section and length did you install for the MPPT battery side ?

Is the charging amps shown on your Smart Solar APP equal to the one shown on your BMV (all other DC charging and load devices shut) ?

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oyster53 avatar image
oyster53 answered ·

Solar panel output won't exceed 6A so 15A fuse I believe to be adequate. MPPT to battery wires are 10 gauge at 25 feet. A float amperage of .2 A is being shown at victron connect amp but nothing at battery monitor from shunt. I believe the moot takes a reading in the morning and charges accordingly, so perhaps I am missing any charge activity but still the main problem remains that the current battery voltage as indicated in the Connect app is 29.99V but is actually 24.5V. Why would it misread current battery voltage?

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klim8skeptic avatar image klim8skeptic ♦ commented ·

"MPPT to battery wires are 10 gauge at 25 feet "

Personally I would put the mppt next to the battery, so the voltage drop along the mppt to battery cable is minimal.

What does you multimeter read at the mppt battery termimals?

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oyster53 avatar image
oyster53 answered ·

As a further note, it seems that the VC App under Battery is showing the MPPT output float voltage and not the battery voltage. I am confused on why it doesn't sample the Batt voltage separate from the voltage it is producing itself. Any ideas anyone? I turned on a few amps of draw to see if output Amperage would increase but no change. I am sure this is operator error in understanding but would appreciate any guidance for this newbie. Thank you.

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

Have you checked the fuses? A 25A fuse is installed directly at the MPPT.

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