Connecting batteries in series is a common practice in various applications to increase the overall voltage output. However, a common misconception arises regarding the impact of series connections on the battery capacity, specifically in terms of mAh (milliampere-hours). While series connections do increase the voltage, they do not increase the mAh rating of the battery pack. Understanding this distinction is crucial for accurately sizing and managing battery systems.
Understanding Battery Capacity (mAh)
mAh is a measure of the total electrical charge a battery can store and deliver. It represents the amount of current (in milliamperes) the battery can provide over a specific period (in hours). A higher mAh rating signifies a larger capacity, meaning the battery can supply more current for a longer duration.
Series Connections and Voltage Increase
When batteries are connected in series, their positive (+) terminal of one battery is connected to the negative (-) terminal of the next battery. This arrangement effectively stacks the individual cell voltages, resulting in a higher overall voltage output. For example, connecting two 3.7V lithium-ion cells in series will produce a 7.4V output.
Why mAh Doesn't Increase in Series
While the voltage increases in a series connection, the mAh rating remains the same. The reason lies in the fact that the total charge capacity of the battery pack remains the same. Each individual cell in the series connection still has its own inherent mAh rating, and connecting them in series simply changes the voltage output without altering the total charge capacity.
Consider this analogy: Imagine having two buckets of water, each holding 1 liter. Connecting them in series does not create a 2-liter bucket. Instead, you now have two separate 1-liter buckets, but with a higher pressure (voltage) because they are stacked.
Impact on Discharge Time
Despite the constant mAh rating, the discharge time of a series-connected battery pack can be affected due to the increased voltage. The discharge time is determined by dividing the mAh rating by the current draw. With a higher voltage, the same current draw can lead to a faster discharge rate. However, it's important to note that the total energy capacity remains constant, as the energy stored is a product of voltage and charge capacity.
Practical Applications
The concept of series connections and their impact on mAh is important in various applications, including:
- Electric Vehicles (EVs): Series connections are used in EV battery packs to achieve higher voltages required by the electric motors.
- Power Tools: Some power tools utilize series connections to provide higher power output and run time.
- Electronic Devices: Series connections are often used in portable electronics to achieve higher operating voltages.
Conclusion
Connecting batteries in series is an effective way to increase the overall voltage output. However, it's crucial to understand that the mAh rating does not increase in a series connection. The total charge capacity remains the same, while the voltage output increases. Therefore, when designing battery systems, it's essential to carefully consider the voltage requirements and the desired charge capacity to determine the appropriate configuration and number of battery cells. By understanding the principles of series connections and mAh ratings, you can effectively manage and optimize your battery systems for various applications.