You all helped me get a much better grip on this than what I could get from the simple sizing worksheets provided by various vendors.
Based on your comments to up the wattage, get more realistic about MPPT, and properly size the battery, I think I am going to go with something like this:
Three 175W, 35.4V panels in series through an MPPT controller to put about 29amps into four L-16's (740 AH total).
The 106V at the panels will allow me to use small (14AWG) wire for my long run to the cabin, and the 12V battery will power my daily DC load of 83 amp hrs. I'll use a 12V/1500W inverter for my corded power tools.
Feel free to comment, heckle, or ignore at your leisure.
Thanks again for all the help. This site is quality.
-Walt -- Going off-grid before snow falls....
The #14 wire has me wondering. Any less wire losses in MPPT makes more power to the battery. Going up to #12 would be cheap. Even #10 is not much more money. I use #12 for a 50W panel.
When it is finished you will understand what you have, and how it works! G-[ Parent ]
It was the Outback I was looking at. They have a tool that calculates Voc at various temperatures for various panels to see if the MX60/FM60/FM80 can handle it.
The link is: http://www.outbackpower.com/forum/viewtopic.php?f=7&t=2900
Then click on "String Sizing Tool".
The record low temp where I'll be installing the system is -25 degrees F, which made the Voc too high for these controllers.
I have found some 180W and 195W panels with lower voltages, so I can string three together in series and still fall well within the limits of the controllers even at very cold temps.
-Walt[ Parent ]
Size wire to keep losses below 2%. Calculator bottom of the page: http://www.powerstream.com/Wire_Size.htm
The longer the run the thicker the wire. Solar panels are expensive, power loss in the wire becomes expensive. Yes, AL can be used. Make sure you have the right termination for it, etc.
My last comment about batteries!-) Buy the cheapest you can, see how long you can make last. (proper care) If you have not taken care of batteries before, you do not want to experiment on expensive batteries, could be costly. More than one person has ruined a good battery with poor maintenance. Strongly consider the inexpensive automatic watering systems. Last look cost $6/cell (with shopping). My golf cart batteries cost $57 each, have 8. three years and counting. Many claim to get more than 7 years from cheap golf cart batteries. Better batteries may last longer, yet need 14 years due to cost ( ratio). I used cost/watts to compare batteries (watts stored = aHr x volts)
12v x 83ah = 1kwhr per day, not much power!
Consider bus bar vs cables.
Have fun, Scott. [ Parent ]
I was using 3% wire loss, but I'll take your advice and use 2%. I'll think about the cheaper batteries too.
Once the system is built and running, I'll post my set-up from my solar powered laptop and let everyone know how it's working. -Walt[ Parent ]
Good luck hope things work out!
Well Have you looked into Rain water catchment? Some states could be a problem, others OK.
Looked at NM, 2100sqft roof with 5,000 gal tank, supplies water 50gal/day for 4 people. Overall much cheaper to do than a well, unless hand dug.
