Hmmm. Maybe I've been a bit too conservative in my calculations of battery time. I ran some numbers using 220 amp-hr golf batteries and an 80 watt panel and decided it wasn't worth the money. Do me a favor and take a look at my calcs and let me know what you think.
Bruce
Well the shortest day of the year has 8 hours of solar cell charging time the longest day is 14 hours. This is if it is sunny all day! One thing to consider in the calculations is that a solar cell is a constant current source. That is why the lager units us a regulator to keep it from over charging the battery. A constant current source will slow charge with the battery when mostly discharged and fast charge if the battery is 80% or more charged.
The 10 to 30 watt solar cells do not need a regulator, as it will not over charge a high capacity battery. But if the battery is not used for several days it can hold a good float charge to it and keep it at a full charge.
Chuck