You can estimate how many recharges you have available by comparing the storage capacity of a portable battery to that of the battery in your smartphone. This is typically expressed in milliAmp hours (mAh) or Amp-hours (Ah). 2200 mAh, for example, equals 2.2 Ah. Watt-hours (wh) are another capacity measurement. To convert watt-hours to milliampere-hours (mAh): mAh = (Wh / Volts) times 1000
Tip: Energy transfer from one battery to another is not completely electrically efficient. As a result, a power pack with a capacity of 2000 mAh will not fully recharge a 1000 mAh electronics battery twice.
A battery pack with sufficient storage capacity and output voltage to move energy into your device is required to recharge or top off your electronic equipment.
How much is too much? First, determine the storage capacity of your device’s battery. To determine the battery capacity of gadgets with built-in batteries, see the technical specifications. This is not an issue if your gadget uses replaceable AA batteries. Choose a battery pack that includes these features.
Power output: The charger’s output (measured in volts) must be equivalent to your electronic device’s input battery voltage requirement. If it’s lower, you may end up draining your device’s battery rather than charging it. Oops!
Most portable battery packs can charge small personal electronics such as mobile phones and MP3 players, but few can recharge laptop batteries.
A 5V output rating is required for small electrical devices that can be charged via a USB connection. Larger electrical equipment that requires a DC power input, such as laptop computers, may require a 12V – 24V output rating. The largest portable battery packs offer this.
The technology of batteries: Portable battery packs differ in capacity and output and terms of technology, size, and weight.
NiMH (Nickel Metal Hydride) batteries are most likely AA or AAA rechargeable batteries. A battery pack that incorporates these is a practical choice for devices that use changeable batteries, such as a GPS, camera, or headlamp. Rather than charging your gadget, simply swap out the batteries.
The most prevalent portable battery packs are lithium-ion and lithium polymers, which use the same technology as built-in batteries in personal electronics.
Lead-acid batteries are big and heavy, but they have the most powerful capacity and output.
Output connectors and adapter tips: If you purchase a solar panel with an integrated or independent battery, any necessary connectors between the panel and the battery will be supplied.
If you purchase a solar panel and battery separately, take note of the output connector and whether it is suitable for charging your device directly (if advised) or connecting to a separate battery pack. A USB (standard, mini, or micro), a connection (with various adapter tips), or a DC output with voltage control are all possibilities.
Utilization of Power
How do you determine your electronic device’s voltage input rating? 1) Look under technical specs in your owner’s manual, or 2) Look for the voltage rating printed or stamped as “DC output” on the wall outlet charger that came with your device. Then, ensure that your portable battery pack can provide at least the same voltage.
Considerations for Action
Still undecided? Here are some expert recommendations from REI personnel that may be of use.
Duration of the journey: A battery pack may be sufficient for a weekend vacation. However, as it is depleted, it becomes an ineffective weight. Therefore, off-grid travels of a week or more are likely to necessitate the use of a solar charger or another generator.
Tip: Charge your electronics and power pack completely before leaving. Even if you did it a few weeks ago, it doesn’t imply they still have a full charge.
Mode of transportation: For a solar charger to be effective, it must be exposed to direct sunshine for an extended period. Some hobbies, such as cycling and sea kayaking, lend nicely to “on-the-go” solar charging. Backpacking in the open country may be appropriate if the panel can be oriented to face the sun. However, if you’re hiking through dense woodland, there’s no purpose in strapping a solar charger to the top of your bag.
Battery type: If your electronic equipment only takes AA batteries, consider investing in a solar charger that can charge a spare set of batteries while the device’s other batteries are in use. In this manner, instead of carrying spares, you can rotate two sets of batteries.
Avoid emptying the battery of a device before recharging it.
Size and weight: All chargers take up space and weigh something. Is it worthwhile? Do you require unrestricted power at all times? Is one emergency charge sufficient? The more storage capacity a power pack has to deliver many charges, the larger (and heavier) it is. Consider the built-in attachment points on solar chargers: Can they be tied down or staked out, so they don’t blow away in a gust of wind?
Battery packs are a supplement, not a replacement. Therefore, do not expect these products to charge your device’s battery completely.
Every rechargeable battery has a useable life, which is often measured in discharge/recharge cycles. Although not all manufacturers publish this figure, you may expect a battery pack to last at least 500 cycles, with up to 1,000 cycles being normal.