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Paul Carmichael avatar image
Paul Carmichael asked

MPPT dropping into float

I have 2 150/60s and they've been working for years. The panels are on different elevations but split evenly between banks. Yesterday both mppts produced around 17kWh each. Today one of them has been in float all day and the battery is at a reported 85%. The voltage is showing at 48.xx whilst a multimeter shows 52 at both mppts. Tha panels are all a bit grubby with dust, but not obscured. Last night I had the mains connected to top up the batteries, so this morning the ccgx showed 100%. It's been a gloriously sunny day and the batteries have been slowly discharging all day. Is this a known issue? They are both running software 4.2.

mppt charging
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Paul Carmichael avatar image Paul Carmichael commented ·

I just disconnected the pv cable for about 2 minutes and the charger stayed in float mode.

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Alexandra avatar image Alexandra ♦ Paul Carmichael commented ·

@Paul Carmichael

If you connect to it using victron connect does it give you any errors or on the VRM if you are connected?

You could start by updating the firmware and then checking if the settings are correct for your batteries. Then check voltage from the panels - something may have happened in the connections or cables.

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Paul Carmichael avatar image Paul Carmichael Alexandra ♦ commented ·

No errors and I believe the software is up to date (1.42 - the above was a typo). This morning the chargers are working as normal, with the battery voltage at 52 and both mppts on bulk. Yesterday, the mppt that was charging showed a lower pv voltage than the other, but the load would account for that, no? This setup has been running for about 4 years. I think the problem had something to do with the day starting at 100% battery. The mppt got its knickers in a twist and thought the battery was fully charged and so went to sleep for the rest of the day.

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Paul Carmichael avatar image Paul Carmichael Paul Carmichael commented ·

Oh no. Found out that the latest software is 1.50, so tried updating it. Stuck at 88% for about 5 minutes now.

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Trina avatar image Trina Paul Carmichael commented ·

Not sure this is helpful but default update is 3 minutes and if using that your 2 minutes of float might not have changed to reflect something else as it fell perfectly between the check interlude for updating status?

Sounds like other stuff is going on though.

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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

If the voltage at the MPPTs is much higher than at the battery you should take a look at the fuses/switches between the MPPTs and the battery.

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Mark avatar image
Mark answered ·

When you disconnect PV (ideally from a circuit breaker after the MPPT charger has been disabled using the switch in VictronConnect), what does the MPPT read as the PV voltage - is it ~0V? (Alternatively you can just check it at night...)

If the PV voltage is not ~0V in this state then the MPPT may have developed an internal short circuit, leaking battery voltage into the PV side and preventing a 'new day' (new charge cycle) from starting.

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