You'd need 4 amps for 15hours if it's totally flat (hope it's not lead acid). 4 amps at 12v=48w
The panels are rated at 20v though so you actually get less current at 13v. Also the sun doesn't shine all the time, also the winter days are shorter.
I'd go for at least 80 to 100w panel.
The panels may be rated at 100 watts but will give a lower output for most of the year. June/July being the best months. Cloudy days will also not be so good etc.
Ours has a 100 watt panel which I am hoping ill be sufficient.
Also consider you may be using power during the day.
We keep a 100 amp hour battery charged for weeks on end,using 120 amp folding solar panels. Mainly used to power an 80 litre fridge freezer and led lighting.
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Topic: Solar Panels
