Laptop Battery 101: How Do They Work?

cgum · December 2020

Understanding Laptop Battery Packs

Shopping for a replacement laptop battery can be challenging for first-timers. This article will familiarize you with the primary battery technologies that will help you comparatively shop.

How are Batteries Rated

Batteries are typically rated on Voltage (V), milli-Amp hours (mAh), and Watt-hours (Wh).

Wh and mAh are both measurements of battery capacity. When comparing two batteries, their Wh can be directly compared. The higher the number, the higher the capacity, meaning the battery will last longer on a full charge. This is because Wh is a unit that accounts for voltage, as seen in the following equation:

When comparing mAh, one must also consider the voltage. mAh can only be directly compared when the voltages are the same.

A battery's voltage is the difference in electric potential between its positive and negative terminals. What is essential to know regarding voltage is that your replacement battery must match exactly, or be very close to, the original battery's voltage.

How are Individual Battery Cells Applied to Make Up Laptop Battery Packs

Laptop batteries are composed of packs of multiple individual battery cells, similar to how our battery-powered household electronics may take multiple AA-cell batteries.

The two pictured above both have individual cell ratings of 3.7 V and 8.14 Wh. Rearranging the above formula to solve for mAh, we see they are 2200 mAh cells.

These batteries can be arranged in series and parallel configurations. When batteries are in series, their voltages are summed to yield the voltage of the whole pack. When in parallel, their mAh (capacity) is summed. Two of the most common are 4-series and 3-series-2-parallel.

In the 4-series configuration, four cells are placed end to end. All four cells together yield a 3.7 *4 = 14.8 V battery with 2200 mAh capacity.

In the 3-series-2-parallel configuration, three cells are placed end to end and then put parallel to another three cells end to end. This yields a 3.7 * 3 = 11.1 V battery with 2200 * 2 = 4400 mAh capacity.

3.7 V is the most common voltage for laptop battery cells, but 3.6 and 3.65 are also used. That is why 10.8 V (3.6 V * 3) and 14.4 V (3.6 V * 4) batteries are also standard. A 10.8V battery can be used for a laptop that originally had an 11.1 V battery without concern. However, a 14.4 V should not be used for an application that had a 10.8 V battery originally.

Voltage Must be the Same - Capacity can Differ

It would be best if you were careful to understand how your replacement laptop battery's capacity compares to the original's capacity. Third-party battery manufacturers typically use the least expensive materials available, usually the 2200 mAh cells in most cases. 2200, 2600, and 2800 mAh are the most commonly used capacities in laptop batteries. If your original was a 14.8 V, 2800 mAh (41.44 Wh) battery, replacing it with a 2200 mAh (32.56 Wh) battery would yield noticeably shorter battery life.

Conversely, upgrading your original battery is also an option. If a third party manufacturer is creating replacements with higher mAh cells, you may be able to upgrade your battery life. Upgrading in this scenario is perfectly acceptable and does not have any ramifications for the rest of your unit or AC adapter. Check out our selection of replacement batteries and search for your laptop's model number for compatibility information.

Need Help Deciding?

If you are interested in increasing your laptop's battery life, upgrading, or replacing, your battery from an old one may be the necessary fix. To ensure you're getting the correct battery for your machine, please stop into any of our locations. Any of our highly experienced staff would be happy to look at your device and help you pick the perfect part to suit your needs. Find a store near you today!