How do they work and why do I need one. (New boat owner, not the boat just new owner) I don't know anything about them other than they charge batteries so fill me in guys! lp

convience... you hook it up to your batts and leav it that way. when your done fishing just plug your boat in and they charger

oh yeah im selling a 2 bank dual pro charger 125 bucks if you want it!

Rebar, an on-board charger is a very convenient item to have.  When you return from fishing, all you have to do is plug in a power cord to the charger and then forget about it.  The charger senses the charge level of the batteries and automatically turns on and off.  You can leave the charger plugged in indefinitely without harming your batteries.  Now, get on the internet (Google?) and learn all about it for yourself.

Thanks guys, I also have a friend with one and asked him about his today. I'll have to have one but I need a few other things first. lp