Solar Panel Input

With54

I have three strings of solar panels running into breakers at the combiner box. One is 240 watt, the second is two 100 watt panels connected in series and the third is two 50 watt connected in parallel and joined in series with a 120 watt panel. The input from each string was significantly different at the time of instal as shown on the Xantrex Charge Controller. Is this typical or are there other factors at play here? The two 100 watt panels joined in series registered at least 100 watts more than the other two all the times.

BB.

Re: Solar Panel Input

No, it is not... Other than for dirt, crystalline solar panels do not change their output voltage/current very much over time (maybe 20% loss over 20-25 years).

Thin film panels do drop 20% in the first 6 months.

It sounds like bad electrical connections somewhere (could be failing panels too--depending on their construction and mounting).

What is the Vmp of the array (and/or each string) and what is your battery bank voltage?

-Bill

With54

Re: Solar Panel Input

The battery bank voltage is 12. I am not sure what the VMP is for the total array and I am not at the cottage today. The specs on the SHARP 240 states that the Vpmax is 30.1 with an open-circuit voltage of 37.4. However, when the open voltage was checked with a multimeter, I thought it was a little lower than that.

Thanks!

With54

Re: Solar Panel Input

The other string that does not appear to be working has the following specs/configuration: 2 X 50 watts in parallel (VMP =17, open circuit 21and ISC = 3.1) connected in series with a 120 watt panel( VMP =17.1, Isc = 7.71 and open circuit volts of 21.3). The third string (2 X 100 )appears to be producing as expected.

Thanks Again!