Jackie: Congrats on your new boat and you will love the times you have in front of you on your boat.
I made the mistake of 'NOT TRUSTING" the high dollar marine grade on-board charger built into my C-Dory TomCat's system, and did not leave it running while I was away from the docks... The result... I really...really shortened the life of the batteries... and they failed me when I needed them the most. :thdown Had my butt busted too many times for not being in the area of a "simple" battery charger left running in the barn... :teeth

A whole different battery charger than what "should be" mounted in your boat.
Each boat is more often than not wired/rigged differently, based on what folks want on "their" boat, but if an on board marine charging system was wired into your boat, you "should be" fine with it left on charge while you are away from the docks. In fact, it will "exercise" your batteries too.
Now if you have a simple buy it at wal-mart, :thdown not really made for marine use but for car batteries charger with a "slow trickle" charge switch.... put it in the garage at home, get it off your boat, and get a real for sure on board "marine" charging system for your boat.
Do not be afraid to re-address any issues with the dealership you purchased the boat from. Way too much information at a way exciting time for most of us when we are receiving our new-owner orientations on our boats, and the many systems on board. They should expect calls from time to time.

hone

hone
Look in your bag or box of books you received from your dealership when you bought the boat and find the owners manual for the charger. Read it. You need to know and understand how it works, particuarly in different varied climates.
Happy Boating!!