The information given in the ad carefully omits useful specs. The "capacity'" is given in watts, a unit of power, not energy. So you cannot tell the energy capacity of the battery. A car battery sized battery holds about 90 amp-hours of energy.
The only useful fact I see is that the size is 15 by 16 inches. That area is less than half of a 100 watt panel. I have a little folding panel like that which can charge phones, as mentioned in the article. It would be able to maintain an RV battery but not recharge it.