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ckrohmer avatar image
ckrohmer asked

MPPT, PV input shorted ?

A customer has two SmartSolar MPPT 250/85ยดs each connected to 3 strings of 5 x 320 W 37(46) V solar panels that do not start up, blue LED blinks slowly. Voltage on PV input terminales is zero volts, but when connection is opened the solar panels show 207 to 214 Volts. On closing the switch PV terminals show zero volts. The PV input of the MPPTยดs seems to be in short circuit. MPPT shows no PV current, I asume because measuring is behind the short. Can this be repaired ?

MPPT Controllers
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1 Answer
Matthias Lange - DE avatar image
Matthias Lange - DE answered ยท

Have you checked the polarity of the PV cables?
If I remember correctly the MPPT showes 0V input if the PV polarity is reversed.

Edit:
What Panels do you have exactly?
With 46V + temperature coefficient (-0,XX%/ยฐC) you maybe will be over 250V and that will kill the MPPT.

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ckrohmer avatar image ckrohmer commented ยท

the panels are Yingli Solar (China) type YL320P-35b, temp coefficient is 0,148 V/ยฐC, at 0ยฐC voltage will be 248,5 V. We are aware that at temperature lower than 0ยฐC and good sunlight the voltage can be over 250 V and can damage the MPPT, and we have told the customer so.

We will check polarity as soon as we can.

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