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mathewcarter avatar image
mathewcarter asked

Issue with the MPPT reading battery voltage

I have seen others post similar issues, i believe i have tried a large portion of those solutions and whilst it may work for a day or 2, the MPPT will get out of sync and read the wrong voltage and go into the incorrect charging mode and the batteries slowly discharge during the peak of the day.
ive disconnected any other charging points and so the solar charger is the only thing connected to the system... ive attached an overview of my system, other then the solar charger reading the wrong voltage, the settings all appear correct to me....the voltage at the battery connect appears correct, also checked with multimeter, so im not sure why the voltage is wrong at the solar charger thought you might be able to suggest things i could try? or a method of diagnosis to go through... this system has work fine for many months and now it seems out of sync, ive tried disconnecting from the victron network, ive tried factory resets and reconfigures, and reconnected to the victron network... sometimes it will all work perfect and all voltages are correct, batteries charge for a day or so and goes out of sync again

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MPPT Controllers
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klim8skeptic avatar image klim8skeptic ♦ commented ·

@mathewcarter@gmail.com It looks like a bad connection causing the voltage drop between the mppt and SBP.

Check the fuse / breaker (you didnt show one) and the crimp connections. Make sure you use a decent breaker, not a junk audio grade unit.

Another thought would be that the SBP is not functional. You could temporality connect the in and out (with a suitably rated jumper) of the SBP to check if the voltage drop disappears.

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1 Answer
pwfarnell avatar image
pwfarnell answered ·

I am assuming from your diagram that the green lines from the shunt to the Cetbo and Cetbo to the MPPT are VE Direct cables. If so, then you should disable the VE Smart Network, you should not have the Bluetooth network and wired comms at the same time as this may cause errors.

You need to use your DMM (digital multimeter) direct on the MPPT terminals and the battery terminals to see if the voltage is higher at the MPPT than at the battery. If the DMM reads high then you have a poor connection somewhere such as the MPPT terminals or other connections, on either positive or negative cables. You need to check where the voltage drop occurs by measuring voltage at each connection. Do you have any fuses or breakers between the MPPT and battery. Some of the cheap thermal breakers often cause voltage drop.

Once finished on the Cerbo you should enable DVCC and enable SVS (share voltage sense) and SCS (share current sense) and the MPPT will then use values from the SmartShunt.

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oxy avatar image oxy commented ·

I'm also having this voltage drift at SmartSolar issue. It's not wiring.

I wrote up here how I used DVCC to work around it, but there's a different problem with that approch:

https://community.victronenergy.com/questions/238355/setting-dvcc-controlling-bms-to-none-results-in-bm.html?childToView=273331#answer-273331

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