Lithium Battery Configurations and Types of Lithium Cells

A secondary lithium battery functions similarly to primary batteries by supplying power to devices through a discharging process. However, unlike primary batteries, secondary lithium batteries have the advantage of being rechargeable and reusable. For those seeking a thorough comparison of sealed lead acid (SLA) batteries versus lithium batteries, our detailed guide is available for reference. In this article, we will delve deeper into lithium battery cells, examining their configurations, real-world applications, and the unique construction that makes them particularly effective for certain use cases.

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LITHIUM CELL FORM FACTOR

When you open up a lithium battery pack, the first components you encounter are the individual cells along with a circuit board. There are three primary types of cells utilized in lithium batteries: cylindrical, prismatic, and pouch cells. For this discussion, all mentioned cells will specifically be lithium iron phosphate (LiFePO4) cells, which operate at 3.2 volts (V).

CYLINDRICAL LITHIUM CELLS

The cylindrical cell is designed similarly to common household batteries, such as AA batteries, which influenced their initial design when these cells were introduced in the market. These cylindrical lithium cells come in various widths, lengths, and amp-hour ratings, categorized further as energy or power cells. Their versatility allows them to be used in both large and small battery packs with differing capacities and voltages. Particularly, cylindrical cells are optimal for applications requiring smaller amp-hour batteries, including power tools, drones, toys, and medical devices where spatial constraints and weight are critical considerations.

PRISMATIC LITHIUM CELLS

In contrast, prismatic cells have a shape inspired by mostly square compartments for batteries. Commonly found in devices like laptops, prismatic cells are rectangular and provide a higher capacity while occupying a compact area. Available in both energy and power cell types, prismatic cells have the advantage of fitting seamlessly into batteries designed to match the dimensions of sealed lead acid batteries. Their higher lithium content by volume enables more amp-hours per cell compared to cylindrical cells, making them favored for larger battery pack configurations and energy storage systems.

LITHIUM POUCH CELLS

As indicated by the name, a pouch cell consists of a lightweight aluminum foil pouch encasing lithium iron phosphate polymer chemistry, with terminal tabs connected at one end. This innovative form factor maximizes lithium content by volume and is designed for direct use in applications without requiring an external cell case. The advantage of pouch cells lies in their higher power density relative to other cell types, thanks to the compact design and their size.

TYPES OF LITHIUM CELLS

In addition to form factor selection, choosing between a lithium power cell and a lithium energy cell is crucial. Power cells are optimized to deliver high power outputs, while energy cells are geared toward delivering high energy. Understanding these distinctions is essential for effective application deployment.

WHAT IS THE DIFFERENCE BETWEEN A POWER CELL AND AN ENERGY CELL?

All lithium cell types are capable of cycling; however, the intensity and duration of that cycling differ (refer to battery C ratings). Power cells are engineered to provide high current loads in short bursts, making them ideal for high-rate applications such as starters or power tools. On the other hand, energy cells deliver steady, continuous currents over longer durations, making them more suitable for cyclic applications like scooters or e-bikes. While all lithium cells perform effectively in cyclic environments, the operational duration varies—the power tool might need recharging after about an hour of use, whereas a scooter might offer much longer run times.

HOW TO CONFIGURE A LITHIUM PACK (BATTERY)

Once the appropriate cell type has been determined for your lithium battery, the next step involves figuring out the required amp-hours (Ah) and overall voltage for your specific application, alongside the necessary amperage specifications.

As an example, when constructing a battery with a capacity of 125 Ah at 12.8V using 25 Ah, 3.2V prismatic cells, the configuration would necessitate a 4S5P arrangement. This indicates creating four master packs containing five cells in parallel (5P), followed by connecting these packs in series (4S)—culminating in a total of 20 cells. Here, the parallel connection enhances the amp-hour capacity while the series connection raises the voltage. For more information on connecting batteries in series or parallel, feel free to browse our resources.

Different lithium cell form factors exist to provide suitable options in terms of sizes, shapes, and flexibility to accommodate varied battery designs. This versatility also caters to different capacities and voltages, allowing you to select between numerous cylindrical cells or fewer prismatic cells based on your specific requirements.

Moreover, it's critical to take the application type into account. For example, although lithium energy cells could technically construct a starter battery, power cells are much more efficient for this use due to their capacity for higher output. Like lead-acid batteries, using a lithium battery for an unintended application—be it cyclic, starter, or high-rate—will reduce its lifecycle.

To sum up, constructing a lithium battery involves careful evaluation of numerous factors, including the intended application, physical size constraints, voltage, and amp-hour demands. Familiarity with the various lithium configuration alternatives can significantly enhance the efficiency of your battery solution. Should you have further inquiries on this topic, we welcome you to reach out.

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