When you need to extend the operating time of your laptop computer, an external laptop battery may be your best solution. These batteries are gaining popularity in both the consumer and commercial market segments because they allow users to power their computers for longer periods of time than traditional laptop batteries.
External laptop batteries generally use either the lithium-ion (Li-ion) or lithium-polymer (LiPo) battery chemistry. Both of these battery types provide high energy to weight ratios, are proven rechargeable battery technologies and are economically feasible. They are also more environmentally friendly that the older battery chemistries.
External laptop batteries are often also called universal laptop batteries because they are inherently equipped with several features to operate a wide variety of laptop computers. The key features in this regard are the variable voltage outputs and an assortment of power adapters.
The key optional specification in the choice of an extended battery pack is the amount of energy that it will hold, since it is this stored charge that will provide power to operate the laptop computer. Although many laptop batteries are specified with the milliamp-amp hour (MAh) rating of the battery to indicate the battery's storage capacity, the watt-hour (WHr) rating is a better specification because it is more of an absolute value that is independent of the battery's voltage.
Popular consumer versions of these extended laptop battery packs are commonly supplied in the 74-142 WHr rating range. This will generally supply enough power to operate a laptop computer for an additional 5 to 12 hours, depending on the battery's capacity and the power requirements of the computer. These consumer targeted batteries will generally weigh from one and a half to three pounds. Commercial versions of these batteries are typically available in the 200-500 WHr range to maximize your computer's operating time when using them as the remote power source for the laptop.
Attention must be paid to the voltage requirements of the computer when choosing an external laptop battery. Although these batteries will often provide voltages at several discrete intervals, you must make sure that one of these available output voltages is within ±1 volt of your laptop's required voltage. However, since it is common to find these universal batteries provided with three to five different voltage outputs, the same battery can be used to power a number of different laptop PCs with different voltage requirements.
In addition to the voltage requirement, it is necessary to ensure that a power adapter that fits your computer's power port is either included with the battery itself or is available as an option. The chargers that are equipped with these batteries terminate in a plug over which an adapter needs to be placed. In many cases these are called barrel style adapters since they slide over a mini-microphone type plug on the charger's side and have a cylindrical shape.
Although not so much a safety concern, it is also important to make sure that the amperage of the battery pack is equal to or exceeds the amperage requirements of the laptop computer or it will not be able to deliver power to the laptop. This specification is most easily found by looking at the label on the charger that came with the OEM battery and laptop computer.
A distinct benefit that many external batteries offer is their ability to power other devices, such as: PDAs, iPods, digital cameras, portable DVD players and cell phones. USB power cords are supplied with many external batteries that have a 5 volt output to facilitate this.
Most times these external batteries will be able to recharge your laptop computer's internal battery. However, this is dependent on the computer's circuitry and may not always be the case. Some of these batteries and their associated chargers offer an automatic voltage detection of the laptop computer and provide an LED power display to indicate the charge level of the external battery. A few of these batteries require the use of the PC's power adapter to energize the battery, but most are equipped with their own battery charger. Also, some chargers will operate at both 120 and 240 volts making them convenient for international travel and usage. Optional converters are also available to charge these batteries from a 12 volt DC power source, such as a car battery.