How to figure solar capacity as added

Discussion in 'The Projects Forum' started by Lectraplayer, Jul 7, 2015.

  1. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
    If I know what my components are rated for, how do I properly predict the realistic capacity of my solar system in watt-hours or amp-hours? I am basically going to start with a single trolling motor battery paired with a 15 watt-hour panel. Obviously, output will be load times time (55 watt light ran three hours would be 165 watt hours, or about 14 amp-hours at 12 volts, but I need guidance on the input.) In Alabama, how many watt-hours per rated watt-hour can I expect?
  2. Lestraveled

    Well-Known Member

    May 19, 2014
    Generally, a 15 Watt Hour panel, at 12.5 volts, should output about 1 to 1.2 amps under full illumination. So view that panel as light weight trickle charger. It won't do you much good except to keep a fully charged good battery charged. In other words, it won't give you any more fishing time.
  3. #12


    Nov 30, 2010
    There are whole books written about this. It depends on whether you are using a solar tracker, what angle from the horizon you are pointed, what season of the year, how much cloud cover, and on and on and on. I'm good at this, so I just installed one and measured it! West facing at a 2/12 slope in Florida in November on a sunny day through a glass skylight, and I got 10% of the labeled results. Measure it and find out. That will take into account all of the local variables much better than guessing from here.
  4. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
    For a 15 watt panel in Birmingham, AL, would 5 W/H/24, or 120 W/H a day sound like a fair starting point to experiment with? (I'm starting with a couple batteries and a couple lights)

    Also, as my system grows, what type of electrical panel is typically used on a solar storage system? Do I need a special panel or would a couple (readily available) Square D QOB panels suffice? I am an electrician, btw)