How to choose a power bank for college

Buy a slim 10,000 mAh power bank. mAh, short for milliampere-hour, is a way to measure how much energy it holds. In general, 10,000 covers a phone for about one to two full charges, though real results vary by phone and by how it is used.

Why not bigger

Bigger power banks weigh more and take longer to recharge. If you only charge a phone, a large one adds weight to your bag every day. See how to choose a backpack for college for how weight adds up.

When to go bigger

• You charge a tablet or a small laptop. Check the power bank's stated output against what your device needs.
• You are away from sockets for a full day, such as a field trip.

Check these before you buy

• Your port type. Match your phone's cable.
• A cable in the box. Not all packs include one.
• Safety marks and returns. Buy from a seller with a clear return policy. Avoid unmarked units, since poor batteries can be a fire risk.

Flying with one

Airlines have rules about power banks, often limiting size and requiring them in cabin baggage, not checked bags. Check your airline's page before you travel.

One exception

If your dorm has sockets near your desk and you rarely travel, you may not need one. A short spare cable is often a better buy. Test with the 30-wear test: do you run out of battery weekly?

Care and habits

Keep the power bank out of hot places, such as a car or a sunny window. Heat is hard on batteries. Charge it overnight at a desk, not under a pillow. If it swells, gets very hot, or smells odd, stop using it and replace it.

Skip this term

A giant power bank for a phone. It is heavy and you will leave it at home.