Solar Power Backyard Irrigation System

Our Solar Panels came in! These came out of a US warehouse for Banggood.

http://us.banggood.com/Wholesale-Warehouse-12V-30W-Energy-Solar-Panel-Battery-Charger-Polycrystalline-With-5M-Alligator-Clip-Wire-wp-Usa-1013811.html

They were $50 each, and the lion's share of the budget for this project. I believe they are the same model as the Photonic Univerise 30W panel, giving the following specifications -

• Peak power: 30W
• Maximum power voltage: 17.5V
• Maximum power current: 1.71A
• Open circuit voltage: 21.6V
• Short circuit current: 1.85A
• Power allowance range: +/- 3%
• Dimensions: 50.5 x 44.5 x 2.5 cm
• Weight: 3.2 kg
• 4 mounting holes
• 5m of twin core cable attached

Looking closer at the panel, we can see -

I don't know much about solar panels, but I bet they are a bit like batteries and LCD displays. You see, what comes off the assembly line isn't all equal in this stuff. They test them at the end of the line, putting the best units in the "best" pile, and on down the line. My guess is that Photonic's panels are just a bit better than the BangGood .

Here, check out the link at enfsolar, that I found after searching for "SM-30P" We can see that they put the panels into a series, and different models of the exact same panel have different specs.

Hunting further, it looks like the SM-30P is an Ammini Solar panel manufacturer out of India. How about that.

There site at http://www.ammini.com/ seems offline at the moment, but you can read a bit here - http://www.ammini.edu.in/content.aspx?pageid=46

I've been looking to salvage batteries from work. We have lots of old UPS units that are destined for the recycle bin -

In the pile, I found some nice looking 12V batteries that would be good for this system.

So we have 4 12v 18Ah sealed led acid batteries. Looks good. I've charged them up, and they look to have 13+V with no load. Are they REALLY good? Testing will tell.