1gsailor56, do not usea automotive
battery charger. They generally are a ferro-resonant type and will cook a deepcycle battery. They will work on starting batteries. Why not hardwire a Sta-power 10 amp two stage that will charge two batteries at the same time at different rates then keep them on float charge.
You need to use either a two stage or (more expensive three stage). This type will keep your batteries happy and ready to use.
It is real important that deep cycles are charged at a certain voltage then kept at float for a certain voltage. And if you use gel or glasmatt batteries, charging is even more critical.
hope this helps.
Dave R.