How to Differentiate Between Grade A, B, and C LiFePO4 Cells?

When manufacturers produce LiFePO4 cells in the same batch, they classify the cells according to their discharge performance. The classification is generally as follows: A = 2600mAh, B = 2400mAh, C = 2200mAh, D = 2000mAh. These classifications are marked on the battery, and the color of the battery's protection gas cap is also used to differentiate them. During discharge, gases are produced within the battery, and when the gas reaches a certain level, the protection cap on the battery's positive electrode will pop off, signaling the battery is near the end of its design life. This is the source of the A, B, C, D classification. The method was initially used by Sanyo and Panasonic, and it has become the industry standard due to the influence of these companies.

Grade A LiFePO4 Cell Characteristics

Grade A cells are the highest quality cells, featuring premium materials, technology, energy storage, stable charge and discharge, specifications, and constant temperature standards. These cells are typically ordered directly from cell manufacturers. After a series of battery production processes, the cells are finally produced and delivered to customers. Grade A cells have the following characteristics:

• 1. High capacity retention: Even after multiple charge and discharge cycles, they maintain a high capacity, ensuring long device runtime.
• 2. Low internal resistance: Lower internal resistance means less energy loss during discharge, enabling more efficient power delivery to devices.
• 3. Excellent consistency: Grade A cells have high consistency in capacity, voltage, and other parameters, which is crucial for battery pack stability and safety.
• 4. High safety: Grade A cells undergo stringent safety tests, including overcharge, over-discharge, short circuit, and compression tests, ensuring no safety incidents under various usage conditions.

Grade B LiFePO4 Cell Characteristics

Grade B cells are of slightly lower quality than Grade A cells. The defect rate in top-tier manufacturers may be around 2%, while for second- and third-tier manufacturers, it may reach 5%-10%. This is why Grade B cells are produced. The difference between Grade B cells and Grade A cells is typically a slight variation in capacity or the dimensions (length, width, thickness), but their performance is not significantly compromised, and they are also cheaper than Grade A cells. Grade B cells are also considered to be those that have been in storage for 3-6 months without being shipped. The characteristics of Grade B cells include:

• 1. Lower capacity retention: After several charge and discharge cycles, the capacity may decrease, but they are still suitable for applications with less stringent runtime requirements.
• 2. Slightly higher internal resistance: Energy loss is higher compared to Grade A cells, but they are still usable in applications with moderate performance requirements.
• 3. Moderate consistency: Grade B cells have less consistency compared to Grade A cells, but the variation is generally within acceptable limits.
• 4. Safety: They undergo some safety testing, but may present some risk in extreme conditions.

Grade C LiFePO4 Cell Characteristics

Grade C cells are the lowest quality. The performance of Grade C cells, including energy storage, charge/discharge efficiency, and durability, differs significantly from that of Grade A cells. If Grade B cells are stored for more than 8 months without shipment, they can be classified as Grade C. Due to the prolonged storage, self-discharge, dust, and moisture exposure, their performance degrades. The characteristics of Grade C cells are as follows:

• 1. Low capacity retention: The capacity drops significantly even after a short period of use, resulting in short runtime. Grade C cells typically only maintain 50%-60% of the capacity of equivalent Grade A cells, with the best ones reaching 70%.
• 2. High internal resistance: There is a significant loss of energy, and the discharge efficiency is low.
• 3. Poor consistency: There is a large variation in parameters, making these cells unsuitable for battery packs.
• 4. Lower safety: These cells have higher safety risks, such as a higher likelihood of overheating or fire incidents.

How to Differentiate the Grade of LiFePO4 Cells?

• 1. Capacity testing: Use professional battery capacity testing equipment to charge and discharge the cells, comparing their capacity retention. Grade A cells maintain higher capacity, while Grade C cells lose capacity more quickly.
• 2. Internal resistance measurement: Use an internal resistance tester to measure the cells' internal resistance. Grade A cells have lower internal resistance, while Grade C cells have higher internal resistance.
• 3. Consistency testing: Compare the parameters of cells within the same batch, including capacity and voltage. Grade A cells have better consistency, while Grade C cells show larger variation.
• 4. Safety testing: Conduct various safety tests, such as overcharge, over-discharge, and short-circuit tests. Grade A cells perform well in these tests, while Grade C cells may fail some of them.
• 5. Original manufacturer's test report: The test report should include data on internal resistance, voltage, capacity, and product codes (usually matching the information on the QR code). If such information is not available, it is likely a Grade B cell.

Applications for Different Grades of LiFePO4 Cells

Grade A cells are ideal for high-performance and critical applications, such as:

• Electric Vehicles: Where long cycle life and high efficiency are essential.
• Solar Energy Storage: Where reliability and longevity are crucial.
• Medical Devices: Where consistent performance and safety are paramount.

Grade B cells are suitable for less critical, but still important, applications such as:

• Consumer Electronics: Where moderate performance and longevity are sufficient.
• Backup Power Systems: Where occasional use does not warrant the highest grade.
• Electric Bikes and Scooters: Where good performance is needed but at a lower level.

Grade C cells are best for non-critical, low-performance applications, such as:

• Toys and Gadgets: Where performance and longevity are not significant concerns.
• Low-end Consumer Electronics: Where cost is a major factor.
• Prototyping and Testing: Where high quality is not necessary.

How to Source High-Quality LiFePO4 Cells?

1. Research Manufacturers

Start by researching reputable manufacturers known for producing high-quality cells. Look for companies with a proven track record and positive reviews.

2. Verify Specifications

Ensure the specifications provided by the manufacturer match the grade you are seeking. Request detailed test results to verify performance.

3. Check Certifications

Look for certifications such as ISO, CE, and UL, which indicate that the cells meet international quality and safety standards.

4. Request Samples

Request samples to test the cells yourself. This can provide firsthand insight into their performance and quality.

5. Evaluate Supplier Transparency

A reliable supplier will be transparent about their products and willing to provide the necessary documentation to verify the grade of their cells.

6. Evaluate Pricing

While price is not always the sole indicator of quality, a reasonable pricing structure often reflects the balance between product quality and overall value. Be cautious of unusually low prices, as they may indicate compromised quality or hidden costs.

We hope that through this article, you will gain a clearer understanding of the different grades of LiFePO4 batteries and their applications, enabling you to make more informed purchasing decisions and bring greater value to your business.