I need help.

[pruthvi]

Hello Team.

I have got about 12 small pannels in a scrap deal, they all seem to be mono's. They do not have any sought of lables on them, so iam unsure of their ratings. I measured each one of them and all of them read open voltage to be approximatly 5.1 v. And short circuit current of 1.05 amps. When i took a closer look at the pannels they seem to have a blocking diode on both positive and the negative terminals. I tried to connect these in (3 series=15v)×4 parllel expecting to get 60w output(15v*4amp). I live in india and here we get good sunlight. But when i hook up a dc watt meter it only shows 0.5 A and over a time 0.7 Ap. And around 7.5 wattsas out put. Please guide me on where i am going wrong and how to get god out put from these pannels

Thnkyou,

Regardas

Pruthvi

[Sunking]

Where you are going wrong is you do not have a MPPT tracking device. You cannot use a fixed resistance to determine what a panel is doing because they are variable current sources, and the current varies with the amount of sun light striking its surface.

Vmp is roughly .78 x Voc so with 15 Voc should be roughly 11.6 volts. Imp is roughly .9 x Isc or .9 x 4 = 3.6 amps. So you have a total of around 40 watts. What you can do is find you a 50 watt 15 ohm variable reostat and find the MPPT point for a brief second to get a voltage and current reading. Bu tjust easier to use the math I showed you. However you need at least 17 to 18 volts for a 12 volt battery.