I'll be up front and honest: I'm an idiot about this stuff.

I need some sort of charger for the battery on my MotorGuide. My boat has two batts- one for the ship, and one for the TM, which doesn't charge off the alternator (I just learned that). My MotorGuide is a pretty basic 12v 55lb wireless motor. Today was the second time I've used it, and I want to keep using it, but don't want to run the battery dead.

What kind of charger do I need that I can plug it in and let sit unattended? The boat is kept on a lift in a slip, and there is a power outlet nearby. I just don't want to buy the wrong thing.

A link to something at Cabelas, Academy, etc. would be helpful so I can see exactly what I'd need. Thanks in advance!