Here's the bottom line...if you have a good battery and a 'smart' charger/controller, plug into shore power, you are good to go...the 'smart' feature will keep your battery from becoming over charged. If you have a good battery, but do not have a 'smart' charger/controller, get one of these: IQ4 Smart Charger/Controller. The IQ4 will keep the charger from over charging the battery. I got my IQ4 here:
http://www.solarseller.com/