generator, boat?

You can use a converter and have it wired in series with one of the batterys to have the same voltage and the combined amps. But the higher rating ones will run you a pretty penny. I suggested the charger becasue you can always have one battery fullly charged so you can start the engine. The other way you can increase the time is a adding an other battery to make it a bank of two battery or more in series to make the amperage higher to have a longer run time and have the other battery for starting the engine when you want to leave(example switch turn to one that will have only one battery for starting engine only and turn to two where you have two or more battery just for playing system, blender , etc when at the sand bar parting) that will give you a longer play time with that set of battery. You can determine play time by the rating of the battery with the amount of amperage you are using. This is just another way but it al depends on the way you want to run the battery charging system and the amount of money you want to spend. Personnally this is the way I have my boat setup (4 12" on one old MTX 225HO to 1ohm load and 6 6-1/2" on a 4 channel MTX ??? model). good luck, VictorIts never to late to do what you love.

Thanks for the info........You mentioned sandbar......do you go to Lake Havasu????