Bruce: I believe 'schottky' is what you were after.
As for the original subject:
"I did some reading and thought maybe I would jump right to the 48 volt system out of the shoot. Everyone says it is supposed to be better and more efficient."
There's a very important aspect in need of addressing in all of this that nobody has touched on yet - one must take into consideration why 48V is more efficient. That which is more efficient electrically is not necessarily more efficient economically. It depends on your usage and future plans, etc.
48V is generally used in the higher power systems because losses in cables, equipment, and the like is reduced because less current flows, yet the power remains the same. Unfortunately, 48V equipment is going to be on the expensive side - the inverters and associated equipment are something like 3KW and up range.
In an optimal 48V configuration with what you have, you'd be producing 180 watts (12 panels, 15W each; the oddballs would have to be left out). Three sets of 4 in series, then the 3 sets paralleled. Right off the bat, you're cutting your throat (unless you're going to buy at least one more panel) by only being able to use 12 of 15 panels.
Next to consider, the main output coming away from the panels would be ~3A at best. This doesn't exactly stress 'normal' wire sizes, and there isn't much loss from it, even on decent runs.
The costs (not to mention headaches) you'll encounter trying to implement this as 48V just don't seem worth it for what you'll get. That's not to say that it wont, but if it were me, I wouldn't do it personally. If you can truly envision a 5KW inverter mounted somewhere near the battery bank at some point in the reasonable future, well, it might be worth it to not have to change over later. If not, forget 48V.
12V is the other end of the spectrum, and with 15 panels in parallel, and while you would get power out of every panel you have, you'd be in significant excess of 15A; a level that begins to really become respectable, and requires consideration for the losses and wire sizes involved. Losses due to heat are the greatest in a 12V system, hence 48V systems being "more efficient". Every resistance in a 12V circuit wastes 4 times the energy that would be wasted at 48V for an equal amount of power.
The balance at those power levels is a 24V system. A common ratio of output to input capabilities is 4:1, so a 1KW inverter would suit nicely. You can get 24V inverters for a reasonable cost (if not flat out free if you know where to look and/or are willing to make a couple sacrifices here and there). You get some of the efficiency back because the heat losses are less, as well as regaining two of your existing panels. 7 paralleled sets of 2 in series, leaving only one in the "dark". (Sorry, couldn't resist.)
You'd be at 210 watts input, 24V at ~8.75A - Manageable without digging too deep in the wallet to cover the wire costs.
Also, you were mentioning current levels not appearing to be what they should be. Just want to point out that any part of a panel that is shaded not only doesn't produce power, it acts as a valve and doesn't let it pass either. If the entire surface of every panel is not fully exposed to bright, unobstructed sunlight, the entire set will fail to produce rated power.
Steve
