It completely depends upon the draw of these batteries.For some simple math, use the equation P=VI, where P = watts, v = voltage, and i = current or amps. Batteries commonly run at 14volts, you'll draw several amps, and you'll need more watts going in.For some comparison, my MacBook Pro (laptop) charger draws a full 85 watts to charge in 2-3 hours.You'll need a lot of these panels for three marine batteries. If you're just wanting something to keep the radio going, these panels will do the trick.Also, for connecting to a battery, I'd seriously look at this controller. It needs a minimum of 10 watt input:http://www.backcountry.com/store/BRU0149/Brunton-Solar-Controller-Battery-Charge-Monitor.html