Battery Charging and Storage

Can I store/charge my batteries outside in the boat and maintain them with a 1-2 amp trickle charge safely? If so and I have 4 batteries in the boat is that to many to safely trickle charge at one time. Also if I am at work and not home is that the best idea to do? http://www.bassboatcentral.com/smileys/popcorn.gif

I would not trust a trickle charger on in boat batteries. Best to get an on-board charger that does at least 3 of them.