I suggest the 'smart' Battery Tender Plus from Deltran. It is the one that BMW sells for twice the price at the dealer parts counter. This is much better than running down tanks of gas while you depend on the alternator to charge the battery. It isn't the same as a slow charger.
http://www.amazon.com/BatteryTender-...8423900&sr=8-2
Many of us here use this charger and it has been extremely reliable over time.
For the other question, look into an Optima battery or two.
http://www.optimabatteries.com/publi...eep_cycle.html