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aseid28 avatar image
aseid28 asked

Troubleshooting BlueSolar 100/50 MPPT Not Charging

Hi all,

I have two sets of solar panels; First, one set of two 50watt panels hooked up to a 30a MPPT and it's all working perfectly.

Second, I have three 180watt panels hooked up to a 100/50a MPPT. These three panels connect to three-pronged connectors (one for the positive and negative line each, respectively).

The positive and negative line both connect down at the 100/50a MPPT. If i disconnect them and test them with a Voltmeter on a sunny afternoon, I can see that 18v are flowing through them. I attach them to the 100/50a MPPT. I attach the 100/50a MPPT to the battery. I only get about .67v output, and the MPPT charger stays slowly blinking on "Bulk". I bought the smart dongle to access the device via bluetooth, and it says that the device is off.

So, I know that there are 18v of power flowing through the pos/neg cables from the PV panels. But, when I plug those pos/neg cables into the PV pos/neg inputs, I get 0 charge to the MPPT.

Can anyone help me understand this?


(full context - I actually originally tried this with a 40a MPPT from a different brand and it saw the same performance. I was concerned that somehow I may have undersized teh 40a MPPT, so I upgraded to the 50a Victron one to see if it would fix it, which it didn't).


thanks so much for any help!



MPPT Controllerswiring
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3 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

first off, you should connect the MPPT to the battery BEFORE connecting the PV input to the MPPT. Failing to do this may damage the MPPT.

Are your 3 180 W panels connected in series or parallel to the MPPT? From the 0.67V PV(?) measured, it looks like there is a short on the circuit, or the MPPT over-voltage has tripped in. If the modules have 18V open circuit voltage - then 3 in series should have 54V.

If you are upgrading from a 40A MPPT, it looks like you are using a 12V system. If the 180W modules are wired in parallel, and have 18V VOC, you are marginal on the Vbat +5V starting threshold.

Hope this helps...


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klim8skeptic avatar image
klim8skeptic answered ·

If the op is using premade mc4 leads, there could be confusion regarding plug gender/cable colour/polarity markings.

mc4.pngImage Caption


The connector with the o'ring, has a + markings is female.

20220813-180818.jpg


mc4.png (81.3 KiB)
20220813-180818.jpg (1.6 MiB)
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aseid28 avatar image
aseid28 answered ·

Thanks for the replies! The panels are connected in parallel.

To clarify - when I test the raw positive and negative PV wires (before they plug into the MPPT) they are giving me 18v. So, I’d think that would indicate that it’s not a polarity issue? (I could def be wrong here, would love to better understand).

So, it gets 18v going into the MPPT but less than 1v going out. Shouldn’t that power be charging the MPPT?

Sorry for being dense :(


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klim8skeptic avatar image klim8skeptic ♦ commented ·
If the polarity is wrong, the mppt will short out the pv array.

Dont trust color coding of pre made cables, check polarity with your multimeter.

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