A122S battery charging

I got an A122S that I picked up late in 2015. Only have used it once and ran the lights off of the battery. Not exactly sure about charging the battery. I believe the battery charges while being towed but what about when it is plugged into the 30 amp land line? Does this also charge the battery? Also when I plug it into the land line there is a little fan by the breaker panel that runs. Is this normal?
Thanks Roger