If you've walked into a store or browsed online and saw a 20V drill or a 10.8V drill you may have wondered what happened. The short of it is that you can thank lithium-ion batteries. What you may not realize is that all li-ion drills have different voltages than their predecessors.
Battery technology has been changing all along. We've had lead-acid batteries, alkaline, nickel cadmium, then nickel metal hydride. What all of these batteries have had in common is they're based on a primary cell of 1.5 volts. Higher voltage batteries were simply more of these primary cells hooked up in series. So all voltages were a multiple of the primary cell's voltage.
But lithium-ion batteries can't have a voltage of 1.5. They have a voltage of around 3.6V (there are variations depending on technology used). Like previous batteries, the higher voltages are made up primary cells hooked up in series. But since the base voltage is different, the multiples are also different. Instead of 12V, you may get 10.8V. Instead of 18V, you may get 20V. Just so we're clear, there's probably no true 18V or 12V lithium-ion drills out there. They're either 20V or 10.8V.
All of the manufacturers have had to make a choice when marketing these new drills. It may seem dishonest to you to market a 10.8V drill as a 12V drill. But you should look at it from the manufacturers perspective. For years, they've been making a 12V drill and marketing it as a 12V drill. They get a new battery technology and make the same drill, only better. If they call it 10.8V versus 12V people are going to think it's a smaller category or less powerful. But that's not true. They've made the drill more powerful. They also want to offer a consistent line of products to their customers and not confuse them.
But different manufacturers have chosen different naming schemes and so there's confusion either way. (That's why I wrote this page; to clear things up ;) To sum things up, all li-ion battery drills are different voltages than the traditional categories.