Solar wattage and batteries are completely independent. Solar Panels collect energy (sunlight) convert it into electricity to be used/stored.
Batteries store energy chemically and deliver it as electricity. Lead acid batteries (flooded/AGM) have a particular chemistry and their charging profiles taper (you can’t put in as much electricity at the end as you did in the beginning, when the batteries were in a discharged state). As the flooded/AGM batteries get closer to being fully charged (the term float is applicable) the voltage that they can be charged at decreases. Read more “Solar and Batteries”