What does the button on a portable power bank do?

Carrying a portable power bank will make you a very popular person. You’re guaranteed to have at least one friend, family member, or colleague who needs to quickly charge a work iPhone or tablet, making you and your trusty device official lifesavers. Portable chargers are also simple enough that almost anyone can use them; Simply plug in your dying gadget via USB and wait for its battery to recharge. And if your power bank has a single button, it’s most likely used to power your charging station.

It’s not brand specific either: companies like Anker, Mophie, Belkin, and even Raycon (yes, they make power banks) usually include a button, either on the top or side of the charger. Pressing it once may be enough to wake up your charger, or you may need to press and hold for a few seconds to activate it. There are also power banks, such as the Raycon Magic Power Bank 5-in-1, that will automatically start charging a device once connected. For chargers like this, you may be able to press (or long press) the bank button to put the charger to sleep.

This bodes especially well for those who want to cut power to a device without physically unplugging it. A small USB-powered gadget like a fan comes to mind, as do tech like portable LED lights, a set of hand warmers, or a coaster-style hand warmer for coffee drinkers.

Although power cycling is one of the most traditional functions of a power bank button, it can also be used to check the battery status of your charger. Most banks feature a series of LEDs that light up (and sometimes flash) to indicate how much charge remains. When a single LED is lit or strobing, it usually means it’s time to recharge the power bank. And if you have a device with a small LCD screen to track the remaining battery, the bank button probably controls the screen’s wake and sleep functions.

It’s a little rarer, but some chargers with buttons may require a specific sequence of presses or a long press to toggle between settings. For example, this version of the Raycon Magic has a wireless charger that only activates if you press the bank button twice when a Qi-certified device is placed on the charger. If your power bank has a special feature like that, I wouldn’t be surprised if you have to use the button to control it.

Not all portable power banks are equal, so the button functionality on one charger may be very different from another. Your best course of action if you buy one: Read the user manual, how-to reviews, and browse user reviews on sites like Amazon. You can also make your search easier by using CTRL+F (or Command+F) to search for words like “button,” “power,” and “press.”