You don't need a PhD in lithium chemistry, but you should recognize the battery brand. Big names like Samsung, LG, Sony, and Panasonic make reliable cells. If a device uses a no-name cell, be cautious.

Capacity matters too, but not in the way you think. A higher mAh rating means more puffs, but it also means the battery is larger and may take longer to charge. For a first device, look for something in the range of 350–800 mAh—enough for a day of moderate use without being a brick.

And here's a tip: ignore the puff count on disposables. It's often marketing. The real tell is the battery capacity and whether the device has a charge port. A disposable with a micro-USB port is a plus because you can top it up instead of tossing it early.