Originally Posted by Burgeogull
For 3-4 months of summer. The one I looked at is about the same as the one you attached the link too.
And you just want to use the 4 batteries and the 180 Watt panel, without a generator to recharge the batteries?
1) Solar panels are not 100% efficient and are rated in "full sun" at 90 degrees of sun ray incidence. Properly positioned, this condition only happens on a sunny day for one second on one day during the summer due to the sun angle changing over time and the elevation of the sun changing every day. The only way to get 90 degree incidence at all times is to use a motor driven pedestal slaved to track the sun. (expensive proposition for only one panel).
2) Rule of thumb is you get 80% efficiency on sunny days from a fixed system, and 20% efficiency on shady (cloudy) days. The actual number of Watts is then dependent on where you live as some areas get more sun than others.
3) You will also lose about 10% of what comes in from the panels in the inverter and line loss; converting the DC to AC.
4) Any excess panel output not used by your freezer during the day goes into the replacing what was used at night by your batteries. If your panels are only producing the "planning average" of 5 hours per day, you will be hard pressed to replace what came out of your battery with such a small panel.
5) Since you will be producing only 20% of the day (on average), your batteries must be sized to provide the remaining 80% (without going below 50% of rated capacity) and the panels must provide (after generation losses) the 20% load plus the 80% loss from the batteries.
It would be easier to work backwards from the 580 Watt average daily requirement to find out how much battery bank you would need and how much solar panel you would need to keep the bank healthy and still run your freezer.