Brief Overview of Laptop Batteries' Capacity

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Brief Overview of Laptop Batteries' Capacity

Laptop batteries provide laptop computers with their key differentiation from the stationary desktop computers that preceded them. Included as standard in laptop computer purchases, batteries are often replaced by buyers for a number of reasons. Batteries have a limited number of recharge cycles, so laptop users who frequently need to recharge their batteries must purchase replacement batteries at least once during the lifespan of their laptops. Damage to a laptop battery can also necessitate purchasing a replacement battery. Conversely, some laptop users prefer to substitute factory-issued batteries with replacement batteries that have more capacity even though their original batteries are still in working order.

Laptop batteries can be purchased at local computer and office supply centers or online at retailers like eBay. To make the most strategic laptop battery purchases, buyers should research how batteries can provide varying levels of capacity based on certain factors. In most cases, buyers are limited somewhat by the make and model of their laptops when choosing battery capacity because laptop batteries must match the proprietary designs of laptop manufacturers. Because of this, buyers should understand laptop battery power ratings, battery cells, and battery compatibility before shopping for replacement batteries.

Laptop Battery Power Ratings

To protect consumers and create standardisation across the computer industry, the Institute of Electrical and Electronics Engineers (IEEE) regulates the development and ratings of laptop batteries. This creates a marketplace where consumers are better able to contrast and compare the battery capacities of different laptop computer models, knowing that the power ratings of all batteries must conform to IEEE standards. IEEE 1625 outlines the power ratings criteria of laptop batteries based on voltage, milliamp hours, and watts. Buyers should have a basic understanding of these power ratings before shopping for replacement batteries to make informed decisions when comparing models.

Laptop Battery Voltage

When reading the power specifications of a laptop battery, buyers can compare voltage, which is often abbreviated as "V". Voltage signifies the potential energy that a laptop battery can produce to power a laptop. This energy matches the amount of power that a laptop consumes from a standard wall outlet when the laptop is plugged in using a power AC adapter. Laptop batteries typically range from 7.2V to 14.4V, with the higher voltages producing significantly more power than lower voltages.

The appropriate voltage for a replacement laptop battery is determined by the volt rating of a buyer's original battery. Unlike some other battery power ratings, buyers cannot increase the voltage of their laptops. If buyers no longer have their laptop's owner manuals, they can remove their original batteries from their laptops and look at the battery specifications printed on the battery to find the volts. When shopping for laptop batteries, buyers should purchase laptop batteries with voltage ratings that exactly match their original battery voltage, if possible. If the exact match is not available, buyers can choose laptop batteries that have voltage capacities that closely match the original battery.

Laptop Battery Milliamp Hours

The ratings that refer to a laptop battery's milliamp hours are referred to as "mAh" and work in conjunction with voltage to determine the battery's capacity. Unlike voltage, however, the milliamp hours of a replacement battery can be higher or lower than a laptop's original battery. Higher numbers of milliamp hours equal laptop batteries that can generally last longer or process more power-intensive applications, like gaming or creating graphics, than a lower-rated original battery.

Using Milliamp Hours to Determine Battery Runtime

Milliamp hours are used to convey how much capacity a laptop battery contains. If buyers find the milliamp hours in a laptop battery's specifications, they can use that number to estimate how long a battery can last before it needs to be recharged.

Before applying an equation to estimate the battery runtime, buyers should divide a battery's milliamps by 1,000. After that number is converted, buyers can then multiply the number by the battery's voltage rating. For example, a buyer considering a laptop battery rated with 4,400 mAh and 11.1V, would divide 4,400 by 1,000 to get 4.4, and then multiply 4.4 by 11.1 to get 48.84. Buyers would then divide 48.84 by a laptop's watt hours to determine how long the battery can last before being drained.

Laptop Battery Watt Hours

The watt hour (Wh) ratings of a laptop battery indicate how much energy a laptop uses per hour and can be applied by battery laptop buyers to determine the capacity of their batteries. In the example above, it was determined that a 4,400 mAh 11.1V battery would produce 48.84 watts of power per hour. If the watt hour rating of a battery is 20Wh, the laptop uses 20 watts of power per hour.

By dividing the amount of power the battery produces before it needs to be charged by the amount of power the laptop consumes, buyers can estimate the runtime of their batteries. In this example, 48.84 should be divided by 20, which results in 2.442, meaning that the laptop can run for almost 2.5 hours before a charge is needed. This figure relies on a battery being a single-cell battery, but many laptop batteries contain multiple cells, which increase their runtime.

Laptop Battery Cells

To increase the runtime of laptop batteries, manufacturers often create batteries that include multiple cells that run concurrently. These cells are designed to be included in one battery cell pack, so buyers must look at a battery's specifications to know how many cells it contains. In the example of the 4,400 mAh 11.1V battery, it was assumed that the battery contained a single cell and could last about 2.5 hours. If the battery contained two cells, however, the runtime of the battery would double to almost five hours.

Factoring in the number of cells in a battery is the last step in determining the capacity of a laptop battery, and must be included for buyers to get a true sense of a battery's value. In some cases, when comparing laptop batteries, the amount of power produced by one battery cell per hour can roughly equal the amount of power consumed in one hour. Without factoring in the impact of multiple cells, these batteries would appear to be poor purchasing choices. If the battery contains six cells, however, the battery produces six hours of power, which is adequate for many buyers' demands.

Battery Compatibility

When shopping for replacement laptop batteries, buyers are limited in their choices by laptop compatibility issues. Since each laptop manufacturer produces uniquely-designed laptops, replacement batteries must conform to the design specifications of a laptop as much as they must retain the same amount of voltage. Because of this, buyers should not begin shopping until they know the exact make and model of their laptops. This allows buyers to check a battery's specifications adequately for compatibility.

In general, a laptop replacement battery model can only be used with the laptops of a specific manufacturer. Within the product details of the battery is a list of manufacturer's laptop models that are compatible with the battery. Buyers should not assume that a replacement battery can function with every model released by a manufacturer because slight differences between models can lead to a completely new battery design.

Buying Laptop Batteries on eBay

Buyers searching for laptop batteries with a variety of capacities can visit eBay to browse through an extensive selection of new and used batteries. On eBay, buyers can find laptop batteries ranging from two cells to 12 cells or more. To search for laptop batteries, buyers add keywords, like "Dell Inspiron 1545 battery", to eBay's search field. Once a search results list is generated, buyers can add filters to the results to focus choices based on the mAh capacity, compatible product line, brand, or price of a replacement battery.

To troubleshoot any potential problems during a laptop battery sale, buyers should read the information that eBay sellers provide in their product listings. For laptop batteries, this information should include details about a battery's voltage, mAh capacity, watts, condition, and compatibility, as well as seller-specific information like shipping methods and return policies. If buyers need clarification, they can contact sellers directly by using the "Ask a question" option located within each eBay product listing.


Buyers purchase laptop batteries for a number of reasons. Since laptop batteries have a limited number of charges available, laptop users often deplete their batteries before their laptops need to be replaced. Buyers can also be motivated to purchase laptop batteries to increase the processing power or runtime of their laptops.

Since the battery capacity of a laptop is a critical component in its operation, buyers should take some time before shopping to understand how the power ratings of a laptop battery can be used to estimate a battery's runtime. To compute the estimation, buyers can follow a tested equation that compares the amount of power a laptop battery generates against the amount of power the laptop consumes. Buyers should also limit their battery purchases to models that are compatible with a buyer's specific laptop. Once buyers identify the battery capacity and compatibility they need, they can visit eBay to locate a wide assortment of laptop batteries from famous manufacturers.

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