There's a good chance that you are currently sharing the room with a half-dozen or more lithium ion batteries. The computer in front of you has one, your camera has one, your phone has one, the R/C car your kid is racing around your ankles has one. Lithium battery technology is almost everywhere. And, soon, it'll be coming to a boat near you.
Before we start, let's (temporarily) forget everything we know from the lead-acid world: charge profiles, cycle life, equalization, voltage setpoints, monitoring, and so on. Lithium is a completely different animal.