Power Bank Buyer’s Guide

We carry Android smartphone or iphone everywhere, and they are indispensable. When we run out of juice, we are disconnected from rest of the world. We use bluetooth, wifi, GPS and other smartphone apps on a daily basis, and due to such power drain our smartphone batteries usually run out of power middle of the day. Although we can improve battery performance by turning off unnecessary features (or placing the phone in airplane mode) of the smartphone, a power bank comes to rescue when we need extra power. Power Bank is an indispensable tool, but how do you find one that is right for your device? Here are a few things that you need to know before researching for a power bank.

1. Your device battery capacity

Your battery’s capacity is specified in mAh (milli-ampere-hour), which is a measurement of amount of energy a battery can store. The larger the mAh, the bigger capacity it has. You may find your battery capacity on the cover of the battery itself, or you may simply google it. Here are a few examples:

• iPhone5: non-removable Li-Po 1,440 mAh (5.45 W)
• Samsung Galaxy S5: Li-Ion 2,800 mAh
• Samsung Galaxy Note 3: Li-Ion 3,200 mAh
• Sony Xperia Z2: Li-Ion 3,200 mAh

Smartphones with larger screen generally require more power, and hence tablets with even bigger display will require larger capacity batteries.

2. Your battery charger specification

Your battery charger specification is located on the usb adapter bundled with your device. The number you’re looking for are voltage and output current of the adapter. For most smartphone batteries, the output voltage is 5V and the preferred current is 2A. Higher the current, faster it will charge your battery. Your USB adapter connected to 110V outlet will deliver 2A current, whereas a USB cable connected to your laptop will only deliver 0.5A which will take a lot longer to charge your phone.
Once you understand your battery requirements, you can research specifications of desired portable battery charger (power bank). Here are a few things that you’ll look for:

1. Capacity in mAh – must be bigger than your smartphone battery.

Power Bank also has a battery to hold charges, and transfer that energy to smartphone when connected. Again, the battery capacity is measured in mAh. The one with 3200 mAh can store double the amount of energy than the one with 1600 mAh battery.
You’ll need a power bank with at least same size battery cell as your smartphone to complete a one full charge. Doubled cell size on power bank doesn’t necessarily mean you’ll get full two charges out of it. Both Power Bank and Smartphone batteries lose storage capacity over time after multiple charges.

2. Ampere Output – higher ampere faster charge.

Each charger has output ampere, and the higher the ampere the faster it will charge the battery. Charger connected to 110V outlet will deliver 2A, whereas a USB cable connected to your laptop will only deliver 0.5A. The lower the ampere, the longer it will take to fully charge the smartphone. Tablets require more energy, so the power banks with higher Ampere output is preferred to charge tablets.

3. Number of output USB Ports – More is better

Most low capacity power banks come with only 1 USB output port. The larger capacity power banks may come with 2 or more USB ports at higher Ampere output for multiple devices.

4. Type of battery used in Power Bank – Lithium-Polymer is preferred

There are two types of batteries used in power banks: Lithium-Polymer (Li-Po) and Lithium-Ion (Li-Ion). Li-Ion is more common as it has a higher energy density, but has in aging issue which causes to lose capacity over time. Li-Po on the other hand has a lower energy density and higher cost to manufacture, but do not suffer aging as much as Li-Ion and safer from explosion. Most users will recharge their power bank unattended and extended period of time causing the power bank to be overcharged. Low grade battery cells used in power banks can be explosive, so high-grade Lithium-Polymer batteries are preferred.