New Delhi, Dec. 22 -- Most people believe they no longer need a power bank. Phone batteries are bigger. Charging is faster. You can top up in 20 minutes and get through most of the day. On paper, the problem looks solved. In practice, it isn't. Batteries may have improved, but the way we use our phones has changed even faster. Larger displays, constant data use, navigation, payments, work calls, streaming, and background apps mean that battery life is no longer about capacity alone. Whew! It is about how long a device can keep up once you step away from a charger. That gap between expectation and reality is exactly where power banks still matter.

And that gap is only going to widen, so you should give yourself a capable power bank before...