SP

[lhudson]

Hi,
I bought a couple of used panels this weekend, the rated VOC is 38V. Yesterday in full sun they only got to 29V (obviously open circuit, no load). When I put a load on them, the 250W panels peaked at 140W (using mppt grid tie inverter as load). I'm thinking the panels are bad, would you agree?

When I buy panels in the future, would you expect the VOC to be close to the rated value even on a cloudy day or would you need direct sunlight to achieve this? Are there fractions of the VOC that when missing indicate particular faults, ie, bad diode, dead cells?
Many thanks

 

[binky]

Hi,
I bought a couple of used panels this weekend, the rated VOC is 38V. Yesterday in full sun they only got to 29V (obviously open circuit, no load). When I put a load on them, the 250W panels peaked at 140W (using mppt grid tie inverter as load). I'm thinking the panels are bad, would you agree?

When I buy panels in the future, would you expect the VOC to be close to the rated value even on a cloudy day or would you need direct sunlight to achieve this? Are there fractions of the VOC that when missing indicate particular faults, ie, bad diode, dead cells?
Many thanks

The panels are knackered, you've been sold a .

If you just want an odd panel for a campervan, then you can live with what you have bought, but if you are trying to power your house, I would ditch these - flog them off. The voltages would possibly indicate one string is down, the cells are usually arranged as 3 sets, hence 3 bypass diodes. They could of course, just be old, panels degrade at upto 1% per year (usually less).

 

[lhudson]

The panels are knackered, you've been sold a .

If you just want an odd panel for a campervan, then you can live with what you have bought, but if you are trying to power your house, I would ditch these - flog them off. The voltages would possibly indicate one string is down, the cells are usually arranged as 3 sets, hence 3 bypass diodes. They could of course, just be old, panels degrade at upto 1% per year (usually less).

Thanks for the advice. So on a cloudy day (which is usually is), when I buy my next set should I expect the VOC to be somewhere near the rated value?

 

[binky]

Thanks for the advice. So on a cloudy day (which is usually is), when I buy my next set should I expect the VOC to be somewhere near the rated value?

Yes