# 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
78
5
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
1,957
1,220
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 Expert

Nov 30, 2010
17,324
8,184
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
78
5
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)