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animalector avatar image
animalector asked

MPPT 150/45 Half Solar input voltage

Good evening from Australia.

I have just, for the first time, installed a Victron MPPT 150/45 DC Coupled to a LiFePO4 battery which is connected to a Sungrow SH5K Solar Hybrid inverter..

I connected four Solar panels (2 Series 2 parallel) each panel is 250W, Voc=59V Isc=5.5A, THey are second hand, and pretty old so I'm expecting some degredation. So they should be a long way from the MPPT 150/45's max voltage rating.

All worked ok, for a start, and the battery was charging. The sequence of events is as follows:

10:45am, connect solar panels to MPPT150/45 measure 104V input, Victron reports 104V input

10:46am, switch on the DC breaker from the MPPT to the Battery Bus - So far so good, battery charging at around 8.4A, 440W (from 1000W of old panels, it's a bit low, but they're leaning against a fence, so ok...)

12:12pm, sitch on the DC breaker from Sungrow inverter to the Battery Bus, (DC Couple the two charge sources) observe battery charge current Total reach around 50A into the battery. Previously I maxed out at 42A with the Sungrow alone (so far so good) See Batrium image showing 46A.. #winning

1:08pm, switch off both DC breakers to battery bus. ( it was cloudy, total amps around 5A ) This is to work on the BMS which has a Blockmon balance module reporting low. ( this issue is unrelated, it has been doing this for a few days). I left the solar breaker ON.

------------------ Issue ------------------------

at around 11:45am (ish) on the Victron chart, the voltage drops from around 70V to around 50V THe Battery Current is about the same. I was not actively monitoring at this time.

At 1:08pm when I switch off the DC Breakers, the Solar Voltage climbs back to around 60V, no load.

Some time later (maybe 30 mins) the Solar Voltage drops to around 40V (no load) there is no apparent reason for this.?¿

I did not isolate the Solar input to the MPPT while I was working on the battery because it was "isolated" with both DC Breakers OFF.

The current state is that with 101V approximately on the input, the MPPT reads only 50V (see last image) Additionally, the Victron App says that the Regulator cannot start. (because the input voltage is too low)

Connections are tight.

---------------- Question -----------------------

Has anyone got any ideas on why this might be so? it feels to me like damage to the regulator, but doesn't line up with anything I may have done to cause it. and input voltages are a long way from 150V

Cheers

Andy

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5 Answers
animalector avatar image
animalector answered ·

MPPT 150/45 Replaced by the supplier, replacement works perfectly. Also tested all of the panels, one dud... the rest are within variability of the sun intensity at the time, (it was a spotty day, never true clear sky..)

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ejrossouw avatar image
ejrossouw answered ·

@Animalector The connection and startup and shutdown sequence is important to ensure the MPPT first detects the correct system voltage before then connecting the solar. Also, this should not be when under load. Reverse applies for disconnection. Check that the correct system voltage is set on the charge controller. Indeed damage can occur if this is not followed.

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animalector avatar image
animalector answered ·

Ok thanks for that info. My very first startup was with Solar only, two panels connected in Series for a total of 105V (ish) then I Bluetooth'd in and configured the battery for 48V and set the charge settings to stop at 55V (this is below the Sungrow battery max settings which manage the BMS for balancing.)

I then turned on the DC Breaker to connect the battery and it detected OK and charged. SO I assume all was ok.

I turned off the DC Bat breaker (frist), then turned off the solar breaker so I could Series parallel the panels before the "Sequence of events as noted above"

In general though I do remove the battery load before doing anything else.

The manual suggests that the MPPT can be powered up with solar only, for first boot, and it will default to 12V battery, which it did, but I absolutely changed it to 48V before switching the Battery breaker on, so I don't think that is the issue.

The bit that consufed me, is why 20 mins after I have turned off the battery, did the input voltage just 'drop'?

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ejrossouw avatar image ejrossouw commented ·

I am in conflict with the "The manual suggests that the MPPT can be powered up with solar only," and stand to be corrected if you can point me at the text.

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Otherwise, I will check all the connections are sound, measure the voltages at various points AND keep the batteries connected. Running the MPPT without batteries would not be a supported usecase, so see if this also happens when you follow the manufacturer's instructions and have the battery connected.

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@Animalector PV voltage is unstable and falls below battery charging voltage.

Test each panel's ability to deliver Isc, then look at array cabling to mppt.

Not many 96 cell panels of that era I would consider useful. 3 out of the 4 panels show some sort of defect.

96-cell.png

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animalector avatar image
animalector answered ·

That's just where the sticky tape was that had the panel test info. Having said that, these are 2nd hand panels.. I will test each one in full sunlight to see if there are some better than others.

Why would the multimeter read 101.4V but the Victron only report 50V through the App?, if it was the panels, wouldn't the meter show 50V also?

Page 17.. Powering battery first enables "auto detection" otherwies it defaults to 12V if powered only through the PV, I edited the battery voltage to 48 through the app on first startup...


I'll do some panel testing tomorrow, cheers,

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@Animalector Why would the multimeter read 101.4V but the Victron only report 50V through the App?, if it was the panels, wouldn't the meter show 50V also?

Panel voltage without load is Voc , only gives half of the information.

The ability of the panel to deliver current Isc , is more important.

A faulty panel / array wiring will give Voc, but will not be able to give Isc. That will result in the array voltage dropping under load.

Test a solar panel. Only check 1 panel at a time.

MC4 connectors also fail, check them.

Shade is bad, get rid of it for the test.

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animalector avatar image
animalector answered ·

Quick test this morning taking on people's suggestions:

Both Panels test ok, within 10% of Voc, and within 10% of Isc (actually a bit lower than 10%, but it was only 8am...) Isc = 4.8A and 4.94A, with a Spec of 5.56A...

I'm currently getting 4.5A (ish) from the two panels, in series, with Isc = 5.56A this is about right, but the watts are low...

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klim8skeptic avatar image klim8skeptic ♦ commented ·
@Animalector Given your measured PV voltage does not match the mppt's reported voltage, contact your dealer regarding further advise and replacement.

Give puppy a pat.

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animalector avatar image animalector klim8skeptic ♦ commented ·
I did give the puppy a pat, and I also threw him the ball... A lot....


I'll take it back to the dealer and have a chat to them, thanks.

regards,

Andy

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