How it works: Portable power

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SCREWED WITHOUT YOUR SMARTPHONE? WHEN YOU’RE AWAY FROM THE MAINS AND NEED TO STAY CONNECTED, A POWER BANK CAN BE INVALUABLE.

But not all power banks are created equal. They come in all shapes, sizes, and capacities, and you need to consider several factors—aside from portability and design—when choosing one. Here are four things you need to know:

1. CAPACITY

Note that a power bank will not deliver its full advertised capacity to your device. Some of this energy is lost through heat generated and the internal circuitry of the power bank. Good power banks can give you between 70 and 80 percent, while some, like Anker power banks, can achieve around 85 percent efficiency. This means that if you have a phone with a 3,000mAh battery, you need a 10,000mAh power bank to give you a little over two full charges.

2. RECHARGE CYCLES AND LIFESPAN

Like any other rechargeable batteries, power banks have a recommended recharge cycle. A good power bank will have 500 recharge cycles or thereabouts. This means that if you recharge your power bank once a day, its lifespan is around 500 days. Once this is consumed, your power bank will no longer be able to recharge to its usual capacity.

3. USB CABLE

USB cables have a data wire and a charging wire within the cable itself, and most of them are 28/28 gauge wires, which are notorious for slow charging because power can’t get through as fast. (Note: the first number represents the gauge of the data wire, while the second number represents the gauge of the charging/power wire. The lower the number, the thicker the gauge.)

If you want to speed things up, get a 28/24 gauge cable. The 24 gauge is about 60 percent larger in diameter than the 28 gauge, and can handle two amps of current.

4. AUTO-CUT

To prevent your phone from getting overcharged, choose a power bank with a feature that automatically cuts off the electricity once your phone’s battery is full.

Words KATRINA RIVERE-DIGA First published in Speed February 2015 issue