MPPT 75/15 measures too low PV voltage

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danielkr asked Aug 21, '23

MPPT 75/15 measures too low PV voltage

Hello,

I just arrived at my vacation destination and after the first day of using the Victron Smart Solar controller, it refuses to charge my battery. I purchased the controller last year in August but I am using it for the first time now (just tested it in the backyard last year shortly). We have a clear sunny sky and it charged with a max of ~ 150 W before stopping.

Setup:

Victron Smart Solar MPPT 75/15 controller
Bluetti PV200 foldable solar panel
LiitoKala LiFePo4 battery (4S 10P = 12V, 65Ah, 780Wh in total)

Error:

Victron charger measures:

Battery: 13,34V (correct)
PV voltage only 16,44 V although it is 22,8 V measured with a multimeter directly at the terminals of the Victron device

As a consequence, it stops charging because it requires +5 V higher voltage of the PV panel compared to the battery.

I suppose the charger is defect taking wrong measures but I would like to ask if anyone has had the same issue and the root cause might be different.

Thanks a lot!

With best regards,

Daniel

voltage

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Answer 1 · 2023-08-22T04:03:40Z

kevgermany answered · Aug 22, 2023 at 04:03 AM

It's possible that the MPPT is faulty. But a more likely cause is defective cabling/connectors/isolators between the panels and the MPPT.

Have you checked the voltage at the MPPT with a meter?

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Answer 2 · 2023-08-22T07:34:43Z

danielkr answered · Aug 22, 2023 at 07:34 AM

Thanks for the response. Yes - I did check the voltage right at the MPPT terminals (the screws where you clamp the cables) and noticed the difference between the MPPT measurement and my multimeter.

With regards to cabling I tried two different cables but the result was the same so I would exclude a defect cable as root cause.

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Answer 3 · 2023-08-22T07:56:05Z

seb71 answered · Aug 22, 2023 at 07:56 AM

Does the MPPT show any errors?

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Try a MPPT reset. It might not help, but easy to do, so do it just in case.

Disconnect the PV wires from the MPPT (of by using the PV disconnect switch if you have one).

Disconnect the MPPT from the battery.

Wait 3 minutes.

Connect the MPPT to the battery.

Connect the PV wires to the MPPT.

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