Dual-port charger, charging a phone and external battery at the same time
Photo by Natalie McMillan
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Choosing the Right Charger for your Thru Hike

Many thru hikers and long-distance backpackers carry a mobile phone and portable battery that can be used to re-charge their phones. One overlooked piece of equipment is the charging device, i.e. the device that gets plugged into the wall to recharge the portable battery and/or the phone battery. This post evaluates a variety of chargers and recommends a 12W dual-port charger (pictured above).

Paul Bodnar       Tech on the Trail       09/09/2018
Paul Bodnar
Tech on the Trail
09/09/2018

You may have already figured out how to charge your phone while doing a long backpacking trip: you can carry a portable battery (also known as an external battery) to charge your phone while on the trail. Then when you get to town, you can re-charge the external battery through an electrical outlet. But most people don’t think about the charging device that allows you to recharge your battery or phone directly from an electrical outlet.  It can be a mistake to use the low-wattage charger that comes with your iPhone or Android. This blog post shows you the difference between charging your phone or portable battery with the standard 5W iPhone charger versus charging with a high-wattage charger that you can purchase yourself. NOTE FOR ANDROID USERS: the same principles apply — most Android devices come with a low wattage charger, but you can use your own charger to charge an Android device.

The chargers we tested

Anker 30W Charger

Anker 18W Charger

OUR PICK: Anker Dual Port 12W (each port) Charger

Standard Apple 5W Charger

NOTE: We have no affiliation with Anker and were not paid to do this review. We chose chargers that are the same, popular brand for consistency and relevance.

But first: What is the wattage of my charger?

Get out your magnifying glass and a calculator. The number of watts is voltage multiplied by amps. Somewhere on your charger you will see tiny print that tells you the voltage and amperage of the charger. If amperage is given in milliamps (“mA”), divide by 1000 to get the number of amps. In this case, this typical Android charger is a 3.5-watt charger.

Typical Android charger

Wallts = Volts X Amps, Watts = 5 volts X 0.7 Amps, Watts = 3.5

Watts = Volts X Amps; 5 Volts X 0.7 Amps = 3.5 Watt Charger

Charging an iPhone with different wattage chargers

We drained an iPhone 8 (1821 mAh battery) down to a 21% charge to simulate a typical charging starting point.  We then charged the phone battery using the four chargers shown above and recorded the time and charge level at various times on the phone until the phone was completely charged.  Interestingly, the 12W, 18W, and 30W chargers (high wattage) performed about the same, charging the iPhone from 21% to about 70% in 30 minutes.  The standard Apple 5W charger performed the worst, charging the iPhone from 21% to about 50% after 30 minutes.

iPhone 8 Charge After 30 Minutes

12W is better than 5W. Above 12W, not much difference.

After 60 minutes of charging, you can clearly see a major advantage with the high wattage chargers.  But there is no real advantage above the 12W charger: the 18W and 30W chargers were no faster than the 12W charger.

iPhone 8 Charging Rate from Wall Charger

Charging an external battery with different wattage chargers

We drained an Anker PowerCore II 10000 portable battery down to 0%.  We then charged the external battery using the same four chargers and recorded the time and charge level on the battery until it was completely charged.  The difference between the 5W charger and the high wattage chargers is substantial.  It took more than 7 hours to charge the portable battery with the 5W Apple charger, and only 4 hours with the 18W charger.  The dual port 12W charger took a little less than 5 hours. There was no benefit to using a 30W rather than an 18W charger. (There is no benefit above 18W because the input for the external battery is limited to a maximum of 9 volts at 2 amps, or 18 watts.)

Time to Charge Anker 10000

Charging 2 devices: 12W dual port charger is the big winner

The 12W dual-port charger has a huge advantage if you don’t have hours to kill: it can charge your portable battery and phone simultaneously.  As you see in the chart, the dual charger greatly outperforms all other chargers when it comes to charging both your phone and your external battery.  And you will notice in the other tests that there is not a big jump in performance above 12 watts. Because of the versatility, we recommend a 12W dual-port charger for thru hiking or long-distance backpacking.

Charging Time for 10000mAh and iPhone 8

Bottom Line: we recommend a 12-watt, dual-port charger for two reasons: (1) you can charge 2 devices at one time, and (2) a 12-watt charger provides a substantially faster charging time compared to the standard-issue low-wattage charger that comes with your iPhone or Android.

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About the Author
A man wearing a backpack and carrying an ice axe kneels in the snow.

Paul Bodnar

Paul has always liked hiking and thru-hiked the Pacific Crest Trail in 1997 after college. After years of working in chemistry, he wanted to create a career involving the outdoors, so he hiked the Pacific Crest Trail again in 2010 to do research for his guide book Pocket PCT. He realized that creating a smartphone app for navigating the outdoors would make it easier to keep the data current and provide a better way to navigate. While hiking with Ryan (aka Guthook) in 2010, they decided to work together to create the first comprehensive smartphone guide for the Pacific Crest Trail. Now with the help of a team of great people they have created over 40 guides for trails around the world.