How to Choose and Use Portable Battery Chargers

    The use of personal and portable electronics in the outdoors continues to grow. Devices include digital cameras, music players, cell phones GPS units and emergency locator beacons. Additionally, expeditions are often outfitted with laptop computers, iPads and satellite phones.

Most of these devices rely on an internal rechargeable battery for power. Functionality is lost when the battery is discharged. To meet the need for recharging these devices when a wall outlet is not convenient, a growing choice of portable battery chargers (also called  external battery pack, external back-up battery, external battery charger, portable battery charger, power bank battery, power bank charger, portable power bank )is available. These provide auxiliary power to recharge or operate your device. Most have the versatility to charge a range of electronics, but some are designed for specific items only, like the iPhone.

Quick Tips on Battery Chargers

In a hurry? Here are the key points:

Know the power input requirement (in volts) of your electronic devices. Find a charger that delivers the same or greater output.

Get a power pack if you do weekend trips and want backup emergency power or a single recharge.

Add a solar charging panel to a compatible power pack for longer trips requiring multiple recharges.

Use a stand-alone solar charger if you can get regular exposure to direct sunlight. To do so, it must be practical to have the panel laid out and charging a device during your trip.

Be aware that 1) Some personal electronics cannot be used while they are being charged up, and 2) You cannot charge a device from a power pack while the power pack is being charged by a solar panel.

Start out with your device’s batteries fully charged. A solar panel or power pack may not provide a full recharge.

iPhone users should consider using a charger designed specifically for this purpose.

Shop REI's selection of portable battery chargers.

For a better understanding of these devices, read on.

 

Power Charge Source

Most portable battery chargers feature their own internal rechargeable battery (power pack), which in turn supplies energy to recharge your electronic device. However, the power pack needs to be charged first. Depending on the model, this is accomplished by one or more of the following sources:

Solar panel (built-in or attachable)

Computer (USB)

Vehicle (12V DC power)

Wall outlet (AC power)

Replaceable AA battery

Tip: Generally, you cannot recharge your electronic device while the power pack is being charged.

In some cases, a solar charger does not contain an internal power pack and charges your device directly as it receives solar energy. Or a solar charger can be added to a power pack to charge it in the field.

Some activities like cycle touring and sea kayaking are well suited to “on-the-go” solar charging. Backpacking in open country can be suitable if you can orient the panel to face the sun. But if you are hiking under a deep forest canopy, there is not much point in strapping a solar charger to the top of your pack.

 

Power Output of the Charger

Key consideration: The power output of the charger must be greater than or equal to the battery rating of your electronic device. If it’s not, the charger may drain your device’s battery instead. That’s right, the wrong charger can actually drain your device’s battery instead of charging it up!

This aspect of portable battery chargers is frequently misunderstood, and buying an underpowered charger will only lead to frustration and disappointment (see our customer reviews for a few examples of this).

All portable power devices can recharge a cell phone or music player, but relatively few can recharge a laptop battery. Smartphones fall in the middle. If you own an iPhone, Droid or Blackberry, do some research to make sure you select a portable battery charger that can do the job. Most electronic devices that can be charged via a computer USB cable need a charging source with a 5V output rating.

How do you find the DC input rating for your electronic device? Two ways: 1) Look in your owner’s manual under technical specifications, or 2) Look for the voltage rating printed or stamped as “DC output” on the wall outlet charger that you likely got with your device. Then make sure your portable power supply—which is expressed in milliAmps (mA) and volts (V)—can deliver at least the same amount.

Sometimes the power output is not the problem—it is the USB cable. If you have problems recharging an Apple product, make sure you are using the Apple USB cable that came with your product.

 

Output Connectors and Adaptor Tips

Some portable battery chargers offer just a USB (standard, mini or micro) output connection or cable. Some offer adaptor tips to suit the most common brands of electronic devices, with other tips available as optional accessories. Check to see what sort of connectors you need for your electronics.

Battery Storage Capacity and Charging

The storage capacity of any battery is expressed in Amp hours (Ah) or milliAmp hours (mAh). The rechargeable battery inside your electronic device will have this information printed on it. For example, my cell phone contains an 850 mAh battery. The battery in a power pack will also have a mAh rating, stated in the manufacturer’s technical specifications for the product. This storage capacity determines how much charge the power pack can store and then send out before it in turn needs recharging.

Battery chargers are not 100% electrically efficient. The actual power discharged from a power pack is affected by temperature, voltage fluctuations and discharge rate. Thus, a power pack rated at 2000 mAh is unlikely to fully recharge a 1000 mAh electronics battery twice. However, knowing the storage capacity of your device’s batteries does give you a good approximation of how many recharges to expect from your power pack. Practice with this at home before heading out on a trip.

Battery chargers offer a supplement, not a guarantee. Do not assume that these products will bring your device’s battery up to a full charge. Customers report better success by doing a top-off recharge long before their device’s battery is fully discharged. Avoid completely draining your device’s battery before recharging it.

Tip: Fully charge your devices and power pack right before your trip. Even if you had done so a couple of weeks earlier, it doesn’t mean they are still holding a full charge.

All rechargeable batteries have a usable life, usually measured in discharge/recharge cycles. Unfortunately, not all manufacturers provide this figure, but you can assume a power pack battery will have a minimum life of 500 cycles, with up to 1,000 cycles being common.

Practical Considerations

Your portable battery charger choices include a:

Solar charger only

Solar charger plus power pack

Power pack only

To decide which approach is right for you, think about when you want to use your electronics, the method to recharge them and how often you will recharge them. To do so, consider the following:

Trip duration: For a weekend trip, a power pack may be plenty. However once it is used up, it becomes unproductive weight. Off-the-grid trips of a week or more are likely to need a solar charger component.

Mode of travel: For a solar charger to either recharge a power pack or charge an electronic device directly, it requires lengthy exposure to direct sunlight. Will you be able to meet that requirement? Base campers, boaters, bikers and backpackers may be able to spread out a solar panel and charge on the go. Or maybe not. For example, this requirement may be practical for flat-water boaters, but not for whitewater boaters. Most solar chargers and power packs are rated as weather resistant, but you probably don’t want to risk your electronic device to the dangers of water, dust or pack-grabbing branches.

Battery type: If your electronic devices use only AA batteries, consider a solar charger that can boost up a spare set of batteries while others are in use in the device. This way you can rotate 2 sets of batteries instead of carrying lots of extras.

Size and weight: All chargers take up space and add weight. Is it worth it? Do you need unlimited power no matter what? Or just the one emergency charge from a small power pack? The bigger (and heavier) a power pack, the more storage capacity it has to provide multiple charges for your electronics. For solar chargers, consider what built-in attachment points they have. Can they be tied down or staked out so they don’t disappear in a wind gust?