Nothing is worse than having an amazing smartphone with little or no battery power. Seeing the dreaded "20% battery remaining" pop up as soon as you leave for the day is something I never want to see. Having a portable iPhone charger handy can keep your iPhone charged when it matters most. There are many portable iPhone chargers which can keep your iPhone charged when you are away from the USB or wall outlet, but which is the best? Below are four general categories of portable iPhone chargers to help you make your decision easier.

Standard Car Charger
Car chargers have been around long before the iPhone and continue to be a popular choice. Often times accessory packages include a car charger, which means in most cases users have a car charger for their iPhone from the start. While the car charger is a staple in portable chargers, its functions are quite limited. It's most obvious restriction is the fact you have to be in or around your vehicle to power up.

Battery powered charger
Battery powered mobile device chargers simply transfer the power from standard batteries (such as 2 AA) to your iPhone. Usually they are relatively cheap to buy plus easy to keep charged. Simply pop in the 2 AA (or similar) batteries and you're ready to go. One tip for if you plan on using a battery-powered charger regularly is to use rechargeable batteries. This will save you countless trips to a store as well as save money over time.

iPhone charging case
Charging cases are easy to use and provide ongoing power to your iPhone. Charging cases are basically an iPhone case that has a battery inside. The case surrounds all or most of the iPhone, and it charges an iPhone by connecting to the charging outlet at the bottom of the device. The case can be charged by plugging its charging cord into your computer's USB port (typically a micro or mini USB). Along with an improved battery life, iPhone charging cases also protect your iPhone from being damaged.

iPhone solar charger
iPhone solar chargers are great for anyone who is regular outdoors or by a window. There are two main categories of iPhone solar chargers- solar charging cases (similar standard charging cases) and off device solar chargers (connect to the iPhone via a charging cord). Most solar chargers are also capable of charging up from a USB which is a great way to charge the device faster as well as if there is no sun. With solar chargers you can continue add power to your charger without the need for batteries or an outlet.