Lithium's the word
Enormous advancements in battery and tool technology have made cordless power tools serious contenders. The latest technology in cordless tool batteries is lithium. This natural element is the lightest of all metals, and it's rapidly become the gold standard of cordless battery anatomy. You'll find lithium in the battery cells of the top cordless tools you look at.
But there's much more to it than just what's inside the battery cells. Heat buildup in a cordless tool battery is not good for the battery. This is why certain manufacturers go to great lengths to design the inside of the batteries so the cells are slightly separated, nest in trays to create an air space, and are heavily protected from damage in case you drop a battery pack.
Don't get burned
Many new tools are "smart" and have internal protection in case you try to work the tool too hard. Leading tool companies have started to include electronics in the form of tiny circuit boards that help manage the power output of the batteries so the tool motor is protected. Cheaper cordless tools will actually burn up in your hands because they don't have this overload protection.
Read the reviews
The fascinating thing about cordless tools and batteries is that two tools may look the same and have the same voltage but have strikingly different performance. This is why it's important to read high-quality tool reviews that cut through some of the marketing hype.
Maximize the motor
The internal electronics found in some cordless tool batteries enhance their run time and the actual power delivered. To get maximum run time and power, you have to couple the battery with a state-of-the-art motor that doesn't waste the battery power.
You get what you pay for
The tools with the best batteries and internal components usually cost the most. Less-expensive tools may have lithium batteries, but that doesn't mean the battery is the best, nor does it mean the tool possesses a sleek motor that will perform for years with no burnout.
See the movie
If possible, try to watch videos of the tools in side-by-side tests. Try to see if you can use a cordless tool at a store before you commit to buying it. Read independent tool reviews that address battery life. Look for batteries that have fuel gauges on them.