An important factor affecting the performance of lithium batteries is internal resistance. As a key indicator of lithium battery performance, internal resistance has a profound impact on the battery's discharge performance, charging performance, self-discharge rate, temperature characteristics and cycle life.The influence of lithium battery internal resistance on battery performance1. Lithium battery dischargeIn terms of discharge performance, the greater the internal resistance of the lithium battery, the more voltage is lost during the discharge process, resulting in a decrease in output voltage. In addition, a larger internal resistance will also limit the size of the output current. The size of the lithium battery internal resistance directly affects the discharge capacity of the battery. In scenarios where high power output is required, lithium batteries with larger internal resistance may not be able to meet the demand, resulting in performance degradation.2. Lithium battery chargingIn terms of charging performance, internal resistance also plays a key role. When the internal resistance is large, the charging current will be limited, resulting in a slower charging speed and affecting the charging efficiency of the battery. Especially with the widespread application of fast charging technology, reducing internal resistance has become the key to improving charging performance.3. Internal resistance also affects the self-discharge rate of lithium batteries. Self-discharge refers to the loss of power caused by internal chemical reactions when the battery is not connected to an external circuit. The larger the internal resistance, the higher the self-discharge rate, which will also cause rapid power loss when the battery is not in use.4. The influence of internal resistance on the temperature characteristics of lithium batteriesLithium batteries generate heat when working, and the larger the internal resistance, the more heat is generated. This may not only cause the battery temperature to rise, but also affect the stability and safety of the battery.Optimization measures to reduce the internal resistance of lithium batteries and improve battery performance1. Optimize battery materials: Select positive and negative electrode materials and electrolytes with high conductivity and low polarization effect, which can effectively reduce the internal resistance of the battery.2. Improve battery structure: By optimizing the battery pole design, diaphragm thickness and electrolyte distribution, the internal resistance and polarization effect of the battery can be reduced, thereby reducing the internal resistance.3. Apply BMS management to reduce internal resistance: BMS can accurately control and monitor the battery to avoid problems such as overcharging and discharging and overheating of the battery, so as to keep the internal resistance of the battery at a low level.4. Reduce the internal resistance of lithium batteries by adopting advanced thermal management technology: By adopting advanced thermal management technology to reduce the internal resistance of lithium batteries, such as liquid cooling, air cooling, etc., the operating temperature of the battery can be effectively controlled to reduce the increase in internal resistance caused by temperature increase.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

According to the retail sales data released by relevant institutions, the total sales volume of China's auto market in 2024 will reach 22.892 million units, and the total sales volume of new energy vehicles will reach 10.749 million units, a year-on-year increase of 47.5%. Among them, the sales volume of pure electric models will reach 6.281 million units, accounting for 58.5% of the market.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

Overview of lithium battery pack and frameLithium battery pack mainly consists of a load frame (lower frame, upper frame), lithium battery, high-voltage connection components (such as high-voltage connectors), low-voltage connection components (such as low-voltage connectors), etc.①- Upper frame; ②- Lower frame; ③- Lithium battery pack; ④- High voltage components; ⑤- Low voltage components (included)The lithium battery frame not only serves as a carrier for various components, but also acts as a "bridge" connecting the entire vehicle. The lithium battery is assembled on the vehicle through the lithium battery frame mounting structure.NIOIn order to facilitate installation and maintenance, the load-bearing frame is generally divided into an upper frame and a lower frame. The lower frame mainly carries components and bears more weight of the battery system; the upper frame generally plays a protective role and has a smaller load-bearing requirement;Lower frame designAs the main load-bearing component of the battery system, the lower frame is relatively more complex to design. There are many considerations in the design process, mainly mechanical strength, sealing design, corrosion resistance, lightweight, etc. At present, the lower frame processes used in battery systems include sheet metal processing, cold stamping, extrusion molding, die casting, etc.(1) Design based on vehicle envelope and lithium battery processDifferent lithium battery types and processes are suitable for different frame design schemes.Battery arrangement is carried out according to the selected battery type and its process. The arrangement scheme of the battery in the frame is called grouping technology. The pros and cons of the grouping scheme and whether the frame design meets the standards are important indicators. The grouping efficiency is the proportion of effective weight and effective space of the battery. The higher the effective proportion, the higher the grouping efficiency.Battery frame design needs to consider the arrangement, fixing and thermal management of the battery in the frame.prismatic batteries are mainly arranged vertically along the heightprismatic batteries are arranged vertically along the heightThere are two main ways of fixing: bracket fixing, which is the traditional module solution, and bracket-free fixing, such as the CTP (Cell to Pack) solution, in which the battery cell is directly fixed to the frame with glue.(2) Design based on power and energy densityBattery layout is carried out according to the power and voltage platform required by the vehicle. In this process, the size decomposition from envelope to battery can be preliminarily completed. According to the battery type and the decomposed battery size, the battery energy density, volume density, etc. can be estimated, and the selection and layout plan can be checked again to confirm whether this layout plan meets the current battery technology level of the industry.Different battery systems have different battery voltage platforms, and the number of batteries required to be grouped in the system will also be different.Upper frame designThe upper frame mainly cooperates with the lower frame to form a closed space to protect the internal components of the frame. The selection of the upper frame material mainly considers environmental adaptability, such as high temperature resistance and corrosion resistance; and has a certain strength to meet the structural strength requirements of the battery system. Currently, sheet metal materials and composite materials are mainly used.With the promotion and application of the CTC solution, the upper frame will also be integrated into the chassis of the vehicle.Other auxiliary designs(1) Sealing designThe connection between the upper and lower frames needs to be sealed to achieve waterproof and dustproof functions.(2) Air pressure balance designThere is a pressure difference between the inside and outside of the sealed frame, which is affected by temperature, altitude, etc. Excessive pressure difference will cause additional force on the frame, affect the frame structure, and even cause the frame to explode. Devices such as air pressure balance valves or breathable valves are often used to balance the internal and external pressure differences.Another function of the air pressure balance design is to provide timely air release.(3) Thermal management design(4) Safety designThe frame design also needs to consider corresponding safety protection designs, such as electric shock protection design, extrusion protection, collision protection, thermal runaway protection design, etc.(5) High and low pressure connection designBosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

The core difference between battery capacity and energy① Definition and unitCapacity: measures the ability of a battery to store charge, in Ah or mAh. For example, a 100Ah battery can discharge for 10 hours at a current of 10A.Energy: represents the total electrical energy released by the battery, in Wh or kWh. The calculation formula is Wh = V × Ah. For example, the energy of a 3.2V, 100Ah battery is 320Wh.② Differences in application scenariosCapacity: directly affects the endurance. The larger the capacity, the longer the endurance.Energy: determines the total endurance of the vehicle. The higher the energy density, the longer the endurance at the same volume.③ The significance in actual car purchaseCapacity: pay attention to the endurance, and need to combine the battery capacity and energy density for comprehensive judgment.Energy: pay attention to the energy density of the battery system. High energy density can reduce vehicle weight and improve energy efficiency.When purchasing a EV, you need to make a comprehensive judgment based on the balance of capacity and energy, battery type adaptability, fast charging and low temperature scene requirements

The constant current followed by constant voltage strategy in the lithium battery charging process is designed based on the physical characteristics and safety of the battery. This charging method not only ensures the safety of the battery, but also maximizes its capacity and prolongs its service life.Constant Current Charging StageIn the initial stage of lithium battery charging, the Constant Current (CC) mode is usually used. In this stage, the charger will provide a relatively stable current, which is generally set according to the design parameters of the battery.For a battery with a nominal capacity of 100Ah, a charging rate of 0.5C means a charging current of 50A.The main purpose of constant current charging is to quickly increase the battery voltage to a threshold close to the full charge state. This stage is effective because when the battery power is low, the internal resistance is small and can accept a larger charging current without causing overheating or damage.In addition, since the polarization phenomenon is weak at this time, charging with a larger current will not significantly affect the performance of the battery.Transition from constant current to constant voltageWhen the battery voltage reaches the set cut-off voltage, the constant current charging phase ends and the system automatically switches to Constant Voltage, (CV) mode.Continuing to charge at a constant high current may cause the battery voltage to rise rapidly, exceeding the safety limit, thereby damaging the battery structure and shortening its service life.During the constant voltage charging phase, the charger keeps the output voltage unchanged, but the charging current naturally decreases as the battery is gradually filled. This is because as the number of lithium ions inside increases, it becomes more difficult to further embed into the negative electrode, causing the internal resistance of the battery to rise, thereby reducing the current even at the same external voltage.Constant Voltage Charging PhaseDuring the constant voltage charging phase, the main goal is to gradually reduce the charging current until it reaches a predetermined low level, at which point the battery is considered fully charged.Despite the reduced charging current, the battery terminal voltage remains constant, allowing the remaining energy to be charged efficiently into the battery while avoiding the risk of overcharging.It should be noted that although the constant current charging phase can quickly increase the battery charge, it cannot complete the entire charging process alone. At the end of the constant current charging, there may be some polarization inside the battery, and the actual battery voltage may be lower than the measured voltage. Without subsequent constant voltage charging, the battery may not reach its maximum capacity, and long-term battery health may deteriorate.Polarization and safety considerationsWhen choosing a constant current followed by a constant voltage charging method, the polarization effect inside the battery should also be considered. Polarization refers to the situation in which the actual voltage of the battery is higher than the equilibrium voltage under ideal conditions due to the limitation of the electrochemical reaction rate during the charging process.The degree of polarization increases with the increase of charging current, which may cause the battery voltage to increase abnormally, or even trigger the protection mechanism to terminate charging prematurely. Introducing a constant voltage stage helps to make the ion concentration distribution inside the battery more uniform, reduce the polarization effect, and ensure that the battery can be fully charged without overheating or damage.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

The main reason for wrapping the blue film on the outside of square lithium-ion batteries involves functional requirements and process considerations in many aspects. The following is a detailed explanation:1. Insulation protection and anti-short circuit design:The outer shell of prismatic shell batteries is usually made of metal (such as aluminum alloy). Direct contact may cause short circuits between batteries or external components. The blue film acts as an insulating layer to effectively isolate the metal surface and prevent accidental conduction.Enhanced safety: In scenarios where battery packs are densely arranged, the blue film reduces the risk of short circuits caused by outer shell contact and improves overall safety.2. Anti-corrosion and sealed environmental protection:The blue film can isolate corrosive environmental factors such as moisture, salt spray, acidic and alkaline substances, delay oxidation and rust of the metal shell, and extend battery life.Sealing assistance: Some blue film materials have waterproof and dustproof properties, and cooperate with battery packaging technology to further improve the sealing.3. Mechanical protection against physical damage:During transportation, assembly or use, the blue film can reduce the damage to the battery shell caused by scratches and collisions, and avoid the exposure of the internal structure or electrolyte leakage due to shell damage.Buffering effect: Some blue films are elastic and can absorb slight impacts to protect the structural stability of the internal pole pieces and diaphragms of the battery.4. Thermal management and auxiliary heat dissipation optimization:Some blue film materials have added thermal conductive particles (such as ceramics and graphite) to help evenly distribute the surface temperature of the battery and avoid local overheating. At the same time, dark colors (such as blue) may be more conducive to heat radiation.Insulation function: In extremely high temperature environments, the blue film may serve as an insulation layer to reduce the impact of external heat on the battery.5. Identification and management model distinction:Blue is often used to identify specific battery models, capacities or voltage levels, which facilitates quick identification during sorting and maintenance of the production line.Brand recognition: Manufacturers use unified colors (such as CATL's iconic blue film) to strengthen their brand image and prevent counterfeiting.Traceability information: Some blue films are printed with QR codes or batch numbers, and the color can be combined to quickly trace production data.6. Process and cost optimization Automation adaptation:The blue film has high contrast in the visual inspection system, which is convenient for machine vision positioning, detection of coating integrity, and improved production efficiency.Material cost: Insulation film materials such as blue PET (polyester) are mature and low-cost, balancing performance and economic benefits.7. Special functional requirements Flame retardant performance:Some blue films are added with flame retardants to delay the spread of fire when exposed to high temperatures, meeting battery safety standards.Anti-ultraviolet: Blue pigments may have better UV resistance, delay film aging, and are suitable for outdoor energy storage scenarios.SummaryThe blue film of prismatic shell batteries is not just a simple packaging, but a key component that integrates insulation, protection, thermal management, and identification.Its color selection (blue) may be due to technical considerations (such as heat dissipation, detection adaptation), or it may be part of the manufacturer's brand strategy.In actual applications, the specific characteristics of the blue film will vary depending on the battery application (such as power battery, energy storage battery) and manufacturer design.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack