You can never be too rich, too thin or have too much juice. While most external batteries charge USB devices only, the Energizer XP18000 provides your laptop, phone, tablet or even your camera with a whopping 18,000 additional milliamp hours of additional energy. At 1.1-pounds, the XP18000 isn’t as light as your average phone charger, but is worth its weight in lithium ions. In our tests, the battery was able to add 8 extra hours of endurance to a ThinkPad X230.
When walking around a trade show, I slip the XP18000 in my laptop bag’s internal pocket and connect its wire to my laptop so it can charge as I walk from one location to another. Even better, the battery doubles as an AC adapter, so you can charge both it and your notebook over a single connection.