Most portable chargers operate with the use of hand cranks or photovoltaic (PV) solar cells. Large units may be used to power a wide variety of devices, while smaller chargers might be designed specifically for phones or other gadgets. Some battery chargers that need to be plugged in to alternating current (AC) power may still be referred to as portable due to their size. Portable marine chargers can be solar powered or designed to plug in to shore power. Other portable chargers may be intended to charge car batteries.
The different types of portable chargers can be divided into self powered and externally powered units. Self powered chargers include hand crank and solar units that derive electricity from kinetic energy or the sun. Externally powered units may have a battery pack or need to be plugged in, but remain small enough to be easily portable. These portable charger will often have a built-in handle to facilitate transportation.
Hand crank and solar powered portable chargers are typically the most useful in emergency situations. Since these types of chargers do not require any external power, they can be used to charge batteries in virtually any situation. Hand crank units may require a large amount of physical exertion, while PV chargers will typically need access to direct sunlight. Solar chargers may also be quite compact, with nesting PV cells that can fold down to the size of a key chain fob. These types of designs provide a large PV cell surface area while the device remains very portable.
Other solar chargers can be much larger and are designed to power bigger devices. Portable marine chargers sometimes make use of PV cells. These portable chargers are typically small enough to be picked up and carried around. Other similarly sized chargers may require a connection to AC power. These chargers are typically portable in the sense that they can be easily carried from place to place, rather than in a sense of being independent from external power.
Portable car battery chargers are typically small enough to be stored in a trunk and carried to where they are needed. These devices will usually require AC power to operate, though some may also have solar cells. They also tend to be easier to move around than larger, bulkier units. An alternative is often referred to as a jump pack. These are often gel pack batteries that can be used to jump start a vehicle, rather than actually charging it.