Solar power and battery basics
I started with a single deep-cycle battery and 30-watts (2Amp) of solar panels mounted on top of van. This whole package, if purchased brand new, is less than $300. Over time I have slowly upgraded to two batteries. The batteries are rated at a total of 200 Amp Hours. So, in theory, 200 hours of use at a single Amp draw. Realistically, you cut that number in half as you never want to drain below 50% battery. So, simple math says 100 hours of use at 1Amp draw.
So how much is 1Amp? The easiest answer without going into all the math; Every 15watts that your appliance uses equals 1Amp you are using. So, a TV that consumes 50watts of power, is using 3.3 Amps of my 100Amp budget if used for a whole hour. My laptop, when charging and powered up consumes 60-70 watts (4-5Amps) per hour.
Now, as for keeping the batteries charged each day I have solar panels that total only about 120 watts, or 8Amps, of power at peak sunlight (which is only between 10am and 4pm at this time of the year). For 6 hours per day I can re-capture about 48Amps of power used from the previous day. The other hours of sunlight are capturing some power, but only fractionally. All together, I can recapture roughly 50-60Amp hours of power back into the batteries that I may have used the previous day, or are using today.
My normal daily use would be a few hours of laptop at a cost of roughly 23 Amp hours. Now with some headroom in the solar area, I can operate my fridge when needed, but I rarely do. I can usually have my batteries recharged with only a few hours of all my panels being out. This allows me to drive or use the sun to charge up all my other batteries (flashlights, MP3 player, cell phone, etc) without leaning in my house batteries.
