Battery Knowledge Base
18650 vs 21700 Batteries: Which One is Right for You?
Lithium-ion batteries come in various sizes, but two of the most commonly used types are the 18650 and 21700 cells. These batteries power everything from flashlights and laptops to electric vehicles and drones or robotics. While both share similar technology, they have key differences in size, capacity, and performance. Let’s break down the differences between 18650 and 21700 batteries to help you choose the right one for your application. Size and Dimensions 18650 Battery: 18mm diameter, 65mm length 21700 Battery: 21mm diameter, 70mm length The 21700 is slightly larger in both diameter and length, which directly impacts its energy storage and power output. Capacity and Energy Density 18650: Typically ranges from 2000mAh to 3500mAh 21700: Typically ranges from 3000mAh to 5000mAh Because of its larger size, the 21700 battery can store more energy than an 18650. This means longer runtimes and higher energy density, making it ideal for high-drain applications. Performance and Power Output 18650: Average Max discharge rate of 10A to 35A (varies by model) 21700: Average Max discharge rate of 20A to 50A (varies by model) The 21700 battery generally supports a higher discharge rate, meaning it can deliver more power, which is especially beneficial for high-performance applications like electric vehicles and drones or robotics. Lifespan and Durability 18650: Typically lasts 300-500 charge cycles 21700: Typically lasts 500-1000 charge cycles The 21700 battery often has a longer lifespan due to improved internal design and higher energy capacity, making it a better long-term investment. Weight and Portability 18650: Weighs around 45g 21700: Weighs around 70g While the 21700 battery offers more power and capacity, it is also heavier. If weight is a critical factor, the 18650 may be a better option for portable applications. Which Battery Should You Choose? Choose 18650 if: You need a smaller, lighter battery for applications like flashlights, laptops, or DIY electronics. Choose 21700 if: You need more power, longer battery life, and better performance for demanding applications like electric vehicles, e-bikes, or drones or robotics. Conclusion Both the 18650 and 21700 batteries are excellent choices, but the right one depends on your specific needs. The 18650 battery is more compact and widely available, while the 21700 battery provides higher capacity, better performance, and a longer lifespan. If you need help selecting the best battery for your application, feel free to reach out to our team!
Learn moreLithium-Ion Battery Storage: How Long Can They Last Without Charging?
Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density and long cycle life. However, how long can a lithium-ion battery last without charging, and what are the best practices for storing them? Let’s explore the factors that impact battery longevity and proper storage techniques. How Long Can a Lithium-Ion Battery Last Without Charging? 1. Self-Discharge Rate Lithium-ion batteries naturally lose charge over time due to self-discharge. The rate depends on factors such as temperature, battery chemistry, and charge level at the time of storage. On average: A lithium-ion battery loses 2-3% of its charge per month when stored at room temperature (20-25°C or 68-77°F). Storing at higher temperatures increases the self-discharge rate, leading to faster energy loss. 2. Storage Duration Based on Charge Level Fully charged (100%): A battery stored at full charge can degrade faster due to increased stress on the cells. Partially charged (40-60%): Ideal for long-term storage as it minimizes chemical reactions that cause capacity loss. Fully discharged (0%): Risky because deep discharge can render the battery unusable and cause permanent damage. 3. Expected Shelf Life Without Charging 1-3 months: The battery will retain most of its charge but may need a top-up before use. 6-12 months: The battery may experience significant capacity loss and require recharging before operation. 12+ months: Without periodic recharging, deep discharge can permanently damage the cells, reducing overall capacity. Best Practices for Storing Lithium-Ion Batteries 1. Store at the Right Temperature Keep batteries in a cool, dry place between 15-25°C (59-77°F). Avoid exposing batteries to extreme heat or cold, which accelerates degradation. 2. Maintain Partial Charge for Storage Store batteries at around 40-60% charge to reduce stress on the cells. Recharge every 3-6 months if storing for an extended period to prevent deep discharge. 3. Use a Battery Management System (BMS) A BMS helps regulate charging and discharging, protecting against overvoltage and undervoltage conditions. 4. Avoid Storing in High Humidity Environments Moisture can cause corrosion and short circuits, leading to battery failure. 5. Keep Batteries Away from Metal Objects Prevent accidental short circuits by storing batteries in a non-conductive container. Conclusion Lithium-ion batteries can last for several months to over a year without charging, depending on storage conditions. To maximize battery longevity, store them at moderate temperatures, maintain a partial charge, and periodically check their charge level. By following these best practices, you can ensure your batteries remain in good condition for future use. If you need expert guidance on battery storage or maintenance, our team is here to help!
Learn moreThe Do’s and Don’ts of Charging Your Battery Pack
Properly charging your battery pack is essential for maximizing its lifespan, maintaining performance, and ensuring safety. Whether you're using lithium-ion, lithium-polymer, or LiFePO4 batteries, following the correct charging practices can help you avoid common pitfalls. Here are the key do’s and don’ts when charging your battery pack. Do’s: Best Practices for Charging Your Battery 1. Use the Right Charger Always use a charger that is specifically designed for your battery chemistry and voltage. Mismatched chargers can lead to overcharging, undercharging, or even battery damage. 2. Charge at the Recommended Voltage and Current Follow the manufacturer’s recommended charging voltage and current to prevent overheating and capacity loss. For example: Li-ion/LiPo: Charge at 4.2V per cell LiFePO4: Charge at 3.65V per cell 3. Charge in a Well-Ventilated Area Lithium batteries can generate heat while charging. Ensure that your battery is in a cool, well-ventilated space to prevent overheating and fire hazards. 4. Monitor Charging Progress Avoid leaving your battery pack unattended while charging. Periodically check its temperature and voltage to ensure everything is running smoothly. 5. Disconnect When Fully Charged Once your battery pack reaches full charge, disconnect it from the charger to prevent overcharging and unnecessary stress on the cells. 6. Store Your Battery Properly When Not in Use If you are not using your battery pack for an extended period, store it at around 50% charge in a cool, dry place to minimize degradation. Don’ts: Charging Mistakes to Avoid 1. Don’t Use a Damaged Charger or Battery Cracked chargers, frayed wires, or swollen battery packs can be dangerous. Always inspect your charger and battery before use. 2. Don’t Overcharge Keeping a battery plugged in after it reaches full charge can cause overheating, reduced lifespan, and in extreme cases, thermal runaway. 3. Don’t Charge a Hot or Cold Battery Avoid charging a battery pack that is excessively hot or cold. Ideally, charge batteries at room temperature (15-25°C or 59-77°F) to prevent damage. 4. Don’t Use the Wrong Charging Mode Many smart chargers have different charging modes. Ensure you are using the correct setting for your battery type to avoid incorrect voltage or current levels. 5. Don’t Charge Near Flammable Materials Charge your battery pack on a fire-resistant surface away from flammable objects to reduce the risk of fire in case of a malfunction. 6. Don’t Leave Batteries Plugged in Overnight Although most modern chargers have auto shut-off features, it’s best practice to avoid overnight charging to minimize risks of overcharging and overheating. Conclusion Following these do’s and don’ts when charging your battery pack will help keep it safe, efficient, and long-lasting. Always use the correct charger, monitor the charging process, and avoid potential hazards. If you need assistance choosing the right battery or charger for your application, our team is here to help! Â
Learn moreBattery Voltage Explained: Nominal, Charged, Minimum, and Cut-Off Levels
When selecting a lithium-ion battery pack, understanding its voltage characteristics is crucial for ensuring optimal performance and longevity. Three key voltage terms define a battery's operation: Nominal Voltage, Charged Voltage, and Cut-Off Voltage. Each of these plays a role in how the battery functions and determines its compatibility with different applications. 1. Nominal Voltage: The Standard Operating Voltage What Is Nominal Voltage? Nominal voltage is roughly the average voltage at which a battery operates under normal conditions. It represents a balance between the battery being fully charged and fully discharged. This value is commonly used to specify battery packs and serves as a general reference for comparing different battery chemistries. Example Nominal Voltages for Different Lithium Batteries: Lithium-Ion (Li-ion): 3.6V per cell Lithium-Polymer (LiPo): 3.7V per cell Lithium Iron Phosphate (LiFePO4): 3.2V per cell For a 3S Li-ion battery pack (three cells in series), the nominal voltage would be 10.8V (3.6V × 3). 2. Charged Voltage: The Maximum Voltage When Fully Charged What Is Charged Voltage? Charged voltage (also called full-charge voltage) is the highest voltage a cell reaches when fully charged. Exceeding this voltage can damage the battery and reduce its lifespan, so proper charging is crucial. Example Charged Voltages for Lithium Batteries: Lithium-Ion (Li-ion): 4.2V per cell Lithium-Polymer (LiPo): 4.2V per cell Lithium Iron Phosphate (LiFePO4): 3.65V per cell For a 3S Li-ion battery pack, the fully charged voltage would be 12.6V (4.2V × 3). Why Does Charged Voltage Matter? Ensures the battery delivers maximum energy capacity. Helps determine charging cutoff limits for battery chargers. Overcharging can cause overheating, swelling, and reduced battery life. 3. Minimum Voltage: The Absolute Lowest Safe Voltage What Is Minimum Voltage? Minimum voltage is the absolute lowest voltage a battery cell can reach before severe degradation or damage occurs. While batteries should generally not be discharged this low, it serves as a hard limit for extreme conditions. Example Minimum Voltages for Lithium Batteries: Lithium-Ion (Li-ion): 2.5V per cell Lithium-Polymer (LiPo): 2.8V per cell Lithium Iron Phosphate (LiFePO4): 2.0V per cell For a 3S Li-ion battery pack, the absolute minimum voltage would be 7.5V (2.5V × 3). Why Is Minimum Voltage Important? Going below this voltage can cause irreversible damage to battery cells. If a battery drops below its minimum voltage, it may become unchargeable. Battery management systems (BMS) typically prevent discharge beyond this level. 4. Cut-Off Voltage: The Recommended Safe Discharge Limit What Is Cut-Off Voltage? Cut-off voltage is the recommended minimum voltage where a battery should stop discharging to prevent long-term damage. It is usually about 0.2V higher per cell than the absolute minimum voltage. Example Cut-Off Voltages for Lithium Batteries: Lithium-Ion (Li-ion): 2.7V per cell Lithium-Polymer (LiPo): 3.0V per cell Lithium Iron Phosphate (LiFePO4): 2.2V per cell For a 3S Li-ion battery pack, the recommended cut-off voltage would be 8.1V (2.7V × 3). Why Is Cut-Off Voltage Important? Helps prevent deep discharge, which reduces battery lifespan. Ensures stable performance and long-term usability. Used by battery management systems (BMS) to regulate power usage. Comparing Nominal, Charged, Minimum, and Cut-Off Voltages Battery Type Nominal Voltage Charged Voltage Cut-Off Voltage Minimum Voltage Li-ion 3.6V 4.2V 2.7V 2.5V LiPo 3.7V 4.2V 3.5V 3.0V LiFePO4 3.2V 3.65V 2.7V 2.5V What Is Cut-Off Voltage? Cut-off voltage is the lowest voltage a battery cell should reach before it is considered discharged. Discharging below this level can lead to permanent damage, capacity loss, and battery failure. Example Cut-Off Voltages for Lithium Batteries: Lithium-Ion (Li-ion): 2.5V - 2.8V per cell Lithium-Polymer (LiPo): 3.5V per cell Lithium Iron Phosphate (LiFePO4): 2.7V per cell For a 3S Li-ion battery pack, the cut-off voltage would be 7.5V (2.5V × 3). Why Is Cut-Off Voltage Important? Prevents deep discharge, which can permanently damage the battery. Ensures longer cycle life and stable performance. Battery management systems (BMS) monitor and prevent discharging beyond this level. Conclusion Understanding nominal, charged, and cut-off voltages is essential when choosing a battery pack for your application. Nominal voltage defines the battery’s general operating range, charged voltage determines its full power capacity, and cut-off voltage ensures safe discharge limits. Ensuring your battery operates within these voltage limits will maximize its lifespan and maintain safe performance. If you're unsure which battery pack best fits your needs, our team is here to help! Â
Learn moreUnderstanding Battery Pack Configurations: Series vs. Parallel Explained
Battery pack configurations determine how much power a battery can provide and for how long. Whether you're choosing a battery pack for an electric vehicle, a robotics project, or an energy storage system, understanding the difference between series and parallel connections can help you make the best decision. Series Connection: Increasing Voltage How It Works Think of series connection like stacking batteries in a flashlight. When you place batteries end-to-end, the voltage adds up, giving more power to the device. However, while the total capacity in terms of amp-hours (Ah) remains the same as one battery, the total energy stored, measured in watt-hours (Wh), does increase since watt-hours depend on both voltage and capacity. Formula: Total Voltage (V) = Sum of Individual Cell Voltages Total Capacity (Ah) = Same as a Single Cell Total Current Output (A) = Same as a Single Cell Example: 2S1P Configuration If you connect two 3.6V Li-ion cells (each 4200mAh) in series: Total Voltage = 7.2V (3.6V × 2) Total Capacity = 4200mAh (Same as a single cell) Total Current Output = 40A (Same as a single cell) This means the battery pack can power a device that requires 7.2V but will last as long as a single 4200mAh battery before needing a recharge. Parallel Connection: Increasing Capacity and Current Output How It Works Parallel connection is like adding multiple fuel tanks to a vehicle. Each additional tank increases the total amount of fuel available, allowing the vehicle to travel longer distances and deliver more power when needed. Similarly, each added battery in parallel increases the total energy storage and allows the battery pack to deliver more current to high-power devices. Formula: Total Voltage (V) = Same as a Single Cell Total Capacity (Ah) = Sum of Individual Cell Capacities Total Current Output (A) = Sum of Individual Cell Currents Example: 1S2P Configuration If you connect two 3.6V Li-ion cells (each 4200mAh) in parallel: Total Voltage = 3.6V (Same as a single cell) Total Capacity = 8400mAh (4200mAh × 2) Total Current Output = 80A (40A × 2) This means the battery pack can power a 3.6V device for twice as long as a single cell and supply twice the current for high-power applications. Combining Series and Parallel (S-P Configuration) Many battery packs combine series and parallel connections to get the best of both worlds—higher voltage and longer battery life. Example: 2S2P Configuration If you connect four 3.6V Li-ion cells (each 4200mAh) in a 2S2P configuration: Total Voltage = 7.2V (3.6V × 2 in series) Total Capacity = 8400mAh (4200mAh × 2 in parallel) Total Current Output = 80A (40A × 2 in parallel) This setup can power a 7.2V device and last twice as long as a single 4200mAh cell while also handling higher current loads. Calculating Watt-Hours (Wh) How It Works Watt-hours (Wh) measure the total energy stored in a battery pack. This is calculated by multiplying the total nominal voltage (V) by the total capacity (Ah). This value helps determine how long a battery can power a device. Formula: Watt-Hours (Wh) = Voltage (V) × Capacity (Ah) Example Calculations: 2S1P Configuration: Voltage = 7.2V (3.6V × 2 in series) Capacity = 4.2Ah (4200mAh converted to Ah) Total Energy = 30.24Wh (7.2V × 4.2Ah) 1S2P Configuration: Voltage = 3.6V Capacity = 8.4Ah (4200mAh × 2 in parallel) Total Energy = 30.24Wh (3.6V × 8.4Ah) 2S2P Configuration: Voltage = 7.2V (3.6V × 2 in series) Capacity = 8.4Ah (4200mAh × 2 in parallel) Total Energy = 60.48Wh (7.2V × 8.4Ah) Choosing the Right Configuration Use Series Configuration if you need a higher voltage for motors, power tools, or other high-power applications. Use Parallel Configuration if you need a longer runtime for devices like energy storage systems and backup power supplies. Use a Combined S-P Configuration when both higher voltage and extended capacity are required. Conclusion Battery pack configurations affect how much power your device gets and how long it lasts. Whether you need more voltage, longer runtime, or both, knowing how batteries are connected helps you pick the right pack. If you need help choosing the best battery for your project, our team is here to assist!
Learn moreLi-Ion vs. Li-Po vs. LiFePO4: Which Battery is Best for Your Needs?
When selecting a battery pack for your project, choosing the right chemistry is crucial. Lithium-Ion (Li-ion), Lithium-Polymer (LiPo), and Lithium Iron Phosphate (LiFePO4) are three common types, each with its own strengths and weaknesses. Understanding their differences will help you make the best choice based on your specific needs. 1. Lithium-Ion (Li-ion) Overview Lithium-Ion batteries are one of the most widely used rechargeable battery technologies today. They are commonly found in consumer electronics, electric vehicles, and power tools due to their high energy density and reliability. Pros: High Energy Density – Li-ion batteries store more energy per unit of weight than most other battery types, making them ideal for applications where space and weight are critical. Long Cycle Life – Typically, Li-ion batteries last between 500-1000 charge cycles, depending on the quality and usage. Lower Self-Discharge Rate – These batteries retain their charge longer when not in use compared to other chemistries. Cons: Safety Risks – Li-ion batteries are prone to overheating and thermal runaway if not properly managed. Requires Battery Management System (BMS) – To ensure safety and longevity, Li-ion packs must include a BMS for proper charging and discharging. Limited Lifespan – While longer than some alternatives, their lifespan is shorter compared to LiFePO4 batteries. 2. Lithium-Polymer (LiPo) Overview LiPo batteries are a variation of Li-ion technology that use a polymer electrolyte instead of a liquid one. They are widely used in applications requiring lightweight and high-discharge rates, such as drones, RC vehicles, and some consumer electronics. Pros: Lightweight and Flexible Design – LiPo cells can be made in various shapes and sizes, making them ideal for compact applications. High Discharge Rates – These batteries can deliver high bursts of current, which is essential for performance-driven applications. Lower Internal Resistance – This allows for faster charging and higher efficiency in power delivery. Cons: Shorter Lifespan – LiPo batteries degrade faster than Li-ion, usually lasting around 300-500 cycles. More Prone to Swelling and Damage – If overcharged or punctured, LiPo cells can swell or catch fire. Requires Careful Handling – Due to their sensitive nature, LiPo batteries need proper storage and balanced charging to ensure longevity. 3. Lithium Iron Phosphate (LiFePO4) Overview LiFePO4 batteries are a type of lithium battery known for their superior safety, long lifespan, and stability. They are commonly used in solar energy storage, electric vehicles, and industrial applications. Pros: Exceptional Lifespan – LiFePO4 batteries can last 2000-5000 cycles, making them one of the longest-lasting lithium battery types. High Safety and Stability – These batteries are much more resistant to thermal runaway, overheating, and fire compared to Li-ion and LiPo. Consistent Performance in Extreme Conditions – LiFePO4 batteries perform well in both high and low temperatures, making them ideal for demanding applications. Cons: Lower Energy Density – LiFePO4 batteries have a lower energy density compared to Li-ion, meaning they require more space for the same amount of stored energy. Higher Initial Cost – These batteries are more expensive upfront, though their longer lifespan can offset the cost over time. Heavier Weight – Compared to Li-ion and LiPo, LiFePO4 batteries are bulkier, which can be a downside in weight-sensitive applications. Which Battery Should You Choose? Choose Li-ion if: You need a balance of high energy density, decent lifespan, and affordability, making it ideal for consumer electronics, power tools, and general-purpose applications. Choose LiPo if: You require a lightweight battery with high discharge rates, such as for RC vehicles, drones, and high-performance electronics. Choose LiFePO4 if: Longevity, safety, and stability are top priorities, such as for solar power storage, industrial equipment, and electric vehicles. Understanding the differences between these battery types will help you make an informed decision based on your specific needs. If you need customized battery solutions, our team is here to help!
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