What does Victron Connect Status/Solar/Voltage actually measure?

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mzel asked Mar 13, '23

What does Victron Connect Status/Solar/Voltage actually measure?

My new 12v battery charging system is on a sailboat where shading is unavoidable, so my panels are in parallel. An external voltmeter shows a fairly consistent 19.5v open circuit at the SmartSolar 100/50 input terminals. However, I'm only seeing 14.5v to 18.0v on Victron Connect Status/Solar/Voltage, whether there is charging or not, and it jumps around a lot. In fact, the Status/Solar/Voltage reading appears to be the value used by the controller for satisfying the 5v/1v charging protocols. So, what exactly is the Status/Solar/Voltage value actually measuring?

VictronConnect

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Alexandra ♦ commented · Mar 13, 2023 at 05:02 AM

@mzel

VOC, what you measure with a DMM, the panels are producing 0A. So no load.

The panels then connect to the mppt which tries to work it. The voltage drops under load to produce amps for charging. It is normal for voltage on a panel to drop under load.

So the measurement you see is the panels under load.

Low voltage from panels are also a product of higher panel temperature.

You would benefit from a combination of series and parallel to get a higher string start up voltage.

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Answer 1 · 2023-03-13T05:06:48Z

klim8skeptic answered · Mar 13, 2023 at 05:06 AM

@mzel Your mppt is looking for the maximum power available from your solar panel.

It does this by varying the current drawn from the panel. As a result of this current constantly changing, the voltage output at the panel also varies. The mppt does a calculation on the current and voltage values (volt x current = power) and constantly hunts for the highest power output.

My output from small array this morning.

At the start of the day the sun is not very high, and the panel has shadows across it, PV voltage is low.

At around 8:00am the panel is fully exposed to the sun, allowing the mppt to lock onto the panels Vmp. PV current (power output) rises due to the improving sun to panel angle.

At around 10:30am the battery is full and the mppt goes over to float. Having no current drawn from the panel, the voltage goes up to the panels Voc rating.

pv-output.png (25.6 KiB)

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Answer 2 · 2023-03-13T06:26:08Z

kevgermany answered · Mar 13, 2023 at 06:26 AM

'So, what exactly is the Status/Solar/Voltage value actually measuring?'

Nothing. It's reporting, in this case what the MPPT sees/tells it. At point of connection to the MPPT.

So voltage into the MPPT is panel voltage - losses in cabling to the MPPT. Output voltage is what it pushes to the batteries, but the batteries will see less due to cabling losses.

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Answer 3 · 2023-03-14T18:21:05Z

mzel answered · Mar 14, 2023 at 06:21 PM

Thanks to all for the responses. After some more observation, it's clear I'm getting very little charging, and that this is because of the Victron 5v/1v protocol. It also seems clear that "Solar Voltage" is a measurement taken when the controller presents or creates a load, and it is used for satisfaction of the protocol. The bottom line is that this controller is not suitable for a system using panels producing 19.5voc.

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Alexandra ♦ commented · Mar 15, 2023 at 01:44 PM

@mzel

PWM is the correct choice for 100W or around that solar setups.

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