Technically, all you need to charge a 12v battery is a solar panel with a 12v rating. This can be any solar panel, although the bigger it's, the quicker your battery will charge. Anything under 5–10 watts is not enough, as these will only “trickle charge” your battery very slowly. In general, 12v panels are only available up. For a 12v battery, you'll ideally need a panel of 200 watts to charge a 100ah battery — the most common 12v battery size. Given that a 200-watt panel can produce around 60 amp-hours per day — on a sunny day under ideal conditions — you should be able to fully. Typically, a 100-watt panel produces around 6ah per hour under ideal conditions or roughly 30ah–40ah per day. If you're charging a 100ah battery from a flat, it will take about two days to charge the battery fully. It's important to note that proper battery. A single 200-watt panel should charge a 12v, 100ah battery daily. Alternatively, two 100-watt panels or four 50-watt panels will do the same. It's possible. How long a 12v battery lasts depends on its amp-hour rating, the size of the solar panel that is charging it, and what load you're putting on it. Let's take a 100ah 12v battery as an example.
