Total posts : 45366
I always like to “Overkill” some just to be safe..
I figure a “Charge Zone” between the hours of 10 am till 2 pm as prime charging time. All other charge is just a bonus. With a 20 watt panel in 4 hrs. (with good sunlight) would produce about 6-7 amp hrs. Even with cloudy conditions you should collect at least 2-3 all day. That would work but the battery is a little big. The battery should cycle a little so the plates don’t get built up if you’re using a lead-acid battery. (I don’t like gell cells)
I’d figure somewhere in the 15/20 amp/hr rating. There’s enough panel to bring it back to full if it’s 1/3 drained in a good day and still could operate for at least 2 days with snow covered panels when fully charged. The battery gets a work out but that’s what it needs. Cold temperatures won’t affect it as bad because the acid is getting sturred around some by the charging/discharging cycle. Too big of a battery will learn a power curve and loose a lot of it’s capacity in a year from not working.
Yep.. I would put a charge controller on it. Too much voltage will boil the battery dry. Just for a little more money you can get a one with PWM charging that helps with the plates from getting built up and making the battery last longer with a deeper charge. I use this type in my home and haven’t the need to add water to my batteries in over a year. I load test them and there as good as new being 2 yrs. old
Also, the link of choice would need to be added in to the equation as well. I’m using a cheep pocket radio and I’m sure those links may use a little more..