IH82BL8 in his opening post mentioned lack of isolation devices. So seems that he may be questioning other issues besides just recharging the batteries.
IH82BL8, if when you leave the boat you generally turn the A/B/Both/Off switch to off, and your don't deep drain your batteries on a typical outing, and that you are mainly concerned about re-charging/maintaining the batteries while you are away for say until the next weekend, and you don't want to worry too much about stray currents from other boats in your marina eating away at your zincs when you are plugged into AC 24/7, then maybe think about installing a smallish (say 50w) solar panel and a latest generation charge controller. Last month's Sail magazine has a DIY article about such a solar installation... that also provided enough daily juice to keep the beer cold. And this forum has many threads with excellent info on the topic.
Stu Jackson (the first respondent to your opening post) comments that he almost never plugs his boat in. I am not nearly in his league with expertise in boat electrics, but that has been my approach as well. My small 20w panel (but I am thinking to increase to 50-60W now that solar panel prices has fallen so much over the last several years), easily recharges my bank within a day of a typical day-sail. Although my demand is typically slight -- only the standard instruments, chart plotter and auto-pilot. And if I am on my boat in the berth for say an afternoon, the 20 watt panel keeps up with the drain from my stereo. In seven years at my berth, total AC billed to me by the marina has been 1kw = about $0.17. Only AC used is for watching DVD's making coffee for the occasional over-nighter, and power-tools needed for repairs. So no need to "AC" except for special instances.