Curiosity killed the pocket book

[TimLa]

To avoid the issues with shaded panels in series, we need to install a bypass diode in parallel with each panel. They cost about $0.50 each. The bypass diode will be 'open' when a panel is illuminated, and 'short' when it's in the shade.

My MPPT controller won't start doing it's thing until the panel voltage rises to 5V higher than the battery. By wiring in series, I'm putting a hair over 51 VDC into the controller, and it has all the room in the world to keep the panels at MPP.

-T

[grady]

Made it out to the lake yesterday and pulled up the history. The battery was not at full charge when it started as you can see from the first 2 days it stayed in bulk the entire time. The first 2 days were full sun. The 3rd day was full cloud cover. Charge time in the 13 hours a day with this setup.



It was cloudy and windy today. Did not get out of the marina. Clocked a gust at 34kts. Did some more non scientific testing. Conclusion is my flexible Chinese panels suck. At one point in full cloud cover, panels were putting out 40V charging the battery at 1.1A. Covered 2 panels at at time with a towel. When only one panel was exposed the solar input voltage went to 14V. Obviously bypassing the covered panels. New panel would still charge at .7A, left old panel was at .1A, right old panel was at .3A. So even tho these panels are in series this controller is effecent at converting voltage to current as Victron states. I was still getting the total output of current as if the panels were in paralell. Would still like to test in full sun at one point.

[Highlander]

Grady
So did u finally get the time to finish off ur test results ?

[grady]

Grady
So did u finally get the time to finish off ur test results ?

Have not done anymore testing other than what is above. I have one more new panel I may replace the lowest output panel with. After that I will do some more testing. For now I am satisfied with the setup and it has plenty to keep my system up and running. One 50W panel is enough to charge my batteries in 4 days or so. I have enough battery to have everything on for 2 days (the weekend).

[sailboatmike]

I have a cheapo Solar controller its called a MPPT 20 and its says its MPPT & PWM.

Over the weekend with my 20 Watt panel connected it was showing 1.3amps going into the battery, by this I assume that for my $20 odd dollars the unit really is MPPT, but Im suspect that you can actually buy MPPT for a mere $20

[kadet]

I have a cheapo Solar controller its called a MPPT 20 and its says its MPPT & PWM.

Over the weekend with my 20 Watt panel connected it was showing 1.3amps going into the battery, by this I assume that for my $20 odd dollars the unit really is MPPT, but Im suspect that you can actually buy MPPT for a mere $20

I doubt it to, a 20A MPPT controller should be a hefty beastie with a inductor for voltage regulation and a large heat sink. Even a cheapie chinese one cost almost $100 so for $20 it would have to be fake or the greatest bargain on earth. Was the 1.3amp being reported by the controller or an independent monitor? What voltage was the battery charging at? Because 1.3A at a charge voltage of 14V = 18.2 watts so???

[Seapup]

I doubt it to, a 20A MPPT controller should be a hefty beastie with a inductor for voltage regulation and a large heat sink.

Some neat tear downs showing the differences

3 of the common $20 "MPPT" sold on ebay.

http://www.quan-diy.com/misc/scc/mppt.htm

A comparison showing some midrange PWM and MPPT

http://www.quan-diy.com/misc/scc/epsolar.htm

And some clone MPPT including a victron

http://www.quan-diy.com/misc/scc/fangpusun.htm#blue