All this fuzzy math about hours of sun in 33.3 days is useless and not the way the calculators work.
If you are consuming 12w and generating 60w (4 toy panels), here's some math. 288w/day (12x24) load. According to the sun maps, we are in the 4 hour of sun (average!) area according to the sun calculation charts. (Maine). This means 240w/day (60x4) generated. In such as case, if it's working, you are either running partly on existing battery charge, getting lucky with sunny weather, or not actually drawing 12w load. Provide some overhead for charging, charging inneficiencies, cable loss, charge controller loss, bad weather. What percent overhead is based on how conservative the calculator is. If it's expensive to visit the site, go extra conservative. I really like to see the batteries fully charged as much as possible. If you have batteries that stay fully charged most of the time, they won't freeze when it's -20f. My extra recommended 40w will help the batteries to stay fully charged and provide the overhead your calculations are missing. In cold weather, the AH capacity of the battery shrinks as well. On Wed, Aug 26, 2009 at 11:05:33PM -0500, Mike wrote: > I'm not sure I buy into your math. If I have a repeater site that is > pulling 1A @ 12V, then it is consuming something like 12W, right? If > I have 60W of solar panel (2 toys) then when conditions are optimal, > I have 48W left over to charge the battery. > > Lets say I am REALLY north, and the panels are only producing 45W. I > still am consuming 12W with the radios, and have 33W left over to > charge the battery. If I have an 800AH battery 24 Hours of sun will > run the radios AND fully charge the battery. If the sun shines 24 > hours out of 33.3 days, I will stay ahead of the curve and the > battery will stay charged. > > No sun for 33.3 days and my 800AH battery will finally die. I NEVER > see those conditions here in the midwest. I'll still maintain you > can do a repeater site for $500 in solar power costs and if you > monitor battery condition it will work just fine. > > At 09:54 PM 8/26/2009, you wrote: > >Here in the north, I wouldn't bother with anything less than 100w of > >panel. > > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -- /* Jason Philbrook | Midcoast Internet Solutions - Wireless and DSL KB1IOJ | Broadband Internet Access, Dialup, and Hosting http://f64.nu/ | for Midcoast Maine http://www.midcoast.com/ */ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
