July 5, 2016

How to choose the best portable battery pack for your phone or tablet

By Team Ventev Topic: Portable Power

We’ve joked before that electronics packaging marks look like alphabet soup. So continuing our quest to decode and demystify those specs, it’s time to stir up a new vocabulary lesson: milliamp hours (mAh), volts, and watts.

Knowing what these terms mean — and how they relate to your device’s specs — will help you find the charging option that will power your devices most efficiently.

Volts, current (amps), and watts are used to describe all electricity transfer — that includes wall charging, car charging, battery charging, you name it. mAh relates to the capacity of portable battery packs. Comparing the capacity (mAh) of a portable battery pack to a device’s internal battery capacity (mAh rating) helps you pick the best one for your device.

To understand how mAh, volts, and watts are separate but related, let’s start by better defining each term:

  • Voltage — symbolized with a capital V — indicates the amount of electrical energy that can flow from a power source. Voltage is delivered based on the size of the draw: A phone charger is usually 5V; a U.S. household’s outlets are 120V.
  • Wattage — symbolized with a capital W — is the combination of volts and current (amps), or volts times amps, and explains the rate of electricity flow. You’re probably most familiar with this from lightbulbs.
  • Milliamp hours — abbreviated mAh — is a representation of charge over a time period or charge multiplied by time. mAh describes how many hours of power you’ll get from a portable battery.

Most manufacturers (including Ventev) use capacity (mAh) to show how much charge is in the battery. The volts and amps numbers complement mAh by showing how that charge is delivered. If you see a 3000 mAh charger rated to 5V/2.4A, the battery can give a maximum output of 5 volts, 2.4 amps regardless of how many hours you have left to charge.

That explains the relationship between mAh, volts, and watts, but does it tell you what you need to know to go shopping? Kind of, but you have to do a little homework first.

To know what size battery to buy, you first have to know the size of your phone or tablet’s battery. Check our phone battery capacity chart.

Once you have the mAh of your device, compare it to the mAh rating of whatever portable battery pack you’re looking to buy. It takes a simple calculation to figure out how much juice you’ll be able to get from the battery pack. Just remember to multiply the battery capacity by 0.7 to account for the 20-30 percent energy lost during conversion.

Example 1:

iPhone 6S: 1715 mAh battery

powercell 3015: 3000 mAh

3000 x 0.7 = 2100

2100 / 1715 = 1.22. Your iPhone 6S will get a full charge and then some from the powercell 3015.

Example 2:

Galaxy S7: 3000 mAh battery

powercell 3015: 3000 mAh

3000 x 0.7 = 2100

2100 / 3000 = 0.7. Your Galaxy S7 can probably get a 70 percent charge from the powercell 3015.

We’re not a big fan of manufacturers labeling portable battery packs with “charges your phone X times” claims. Because, as the examples show, the number of charges you get totally depends on the device.

You don’t have to be a math whiz to figure out what size portable battery is best to charge your phone. But if you’re still looking for a straightforward answer, follow these rules:

  • For most phones, a 3000 mAh battery is your best bet for recharging.
  • For tablets and bigger-battery devices, a 6000 mAh battery is the way to go. It also helps if you need to charge your phone twice or help a friend in need of some power.

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