Lithium battery charging and discharging curve analysis and application Original: Lithium Battery Technology Lithium Battery Technology Knowledge Platform Abstract: This article introduces in detail the analysis method of lithium battery charge and discharge curves, including charging efficiency, discharge characteristics, capacity evaluation, internal resistance evaluation and cycle life evaluation. By interpreting the charge and discharge curves, we can gain an in-depth understanding of the performance and characteristics of lithium batteries, providing an important basis for battery selection, use and optimization. 1. Introduction The performance of lithium batteries is crucial to the operation of various electronic devices and power tools. The charge and discharge curve is one of the important means to evaluate the performance of lithium batteries. It can intuitively reflect the voltage and current changes of the battery during the charging and discharging process. By analyzing the charge and discharge curves, information on key parameters such as battery capacity, internal resistance, and efficiency can be obtained, thereby providing guidance for optimizing battery design and improving battery performance. 2. Lithium battery charging curve analysis The charge and discharge curve of a lithium battery is the relationship between the voltage and the discharge capacity of the battery, and is also the curve of the remaining capacity SOC. During the charging process of the lithium battery, the voltage gradually increases and the current gradually decreases. The slope of the charging curve reflects the charging speed. The greater the slope, the faster the charging speed. At the same time, the plateau area of the charging curve indicates that the battery is fully charged, and the voltage tends to be stable at this time. (1). Charging efficiency analysis: Charging efficiency is an important indicator to measure battery charging performance. Higher charging efficiency means that the battery can more effectively convert the input electrical energy into chemical energy and store it. By comparing the actual charging capacity and the theoretical charging capacity of the charging curve, the charging efficiency can be evaluated. In addition, the energy loss during charging can also be observed to find ways to improve charging efficiency. (2). Charge end voltage: Charge end voltage refers to the voltage value when the battery is fully charged. Correctly setting the charge termination voltage can avoid overcharging and extend battery life. By analyzing the charging curve, the appropriate charging termination voltage is determined to ensure that the battery is charged within a safe range. 3. Lithium battery discharge curve analysis During the discharge process, the voltage gradually decreases and the current also decreases. The shape and slope of the discharge curve can also provide important information about battery performance. (1). Discharge characteristic...

What are the relevant parameters of the inverter? Rated output voltage: The rated voltage value that the inverter should output when outputting rated current under specified input power conditions. (Usually the voltage fluctuation range is 220V±5% for single-phase; 380±5% for three-phase.)   Rated output current: The rated output current of the inverter within the specified negative power factor range. Some inverters give rated output capacity, expressed in VA or KVA. The rated capacity of the inverter is the product of the rated output voltage and the rated output current when the output power factor is 1 (pure resistive load).   Starting voltage: Conventional inverters are powered by DC. When the sun is shining, the string voltage will gradually increase. When the string voltage exceeds the starting voltage value, the inverter starts and starts working. (To prevent the inverter from starting repeatedly, the starting voltage is usually higher than the minimum operating voltage.) The lower the starting voltage, the earlier it starts and the longer it takes to generate electricity.   Maximum input voltage: refers to the upper limit of the input voltage that the inverter can withstand. In conjunction with the maximum open circuit voltage of the string, at the lowest temperature, the maximum open circuit voltage of the string does not exceed the maximum DC input voltage.   Maximum Power Point Tracking, abbreviated as MPPT (Maximum Power Point Tracking): The core function of the inverter can track the maximum power generation point of the component under the current situation. Simply put, it can track the voltage. In actual work, the output power can be maximized at the most appropriate voltage. MPPT working voltage range: That is, the range in which MPPT can effectively track the changing voltage of components. Only within this range, the inverter can work normally. The wider the voltage range, the greater the inverter's applicability.   Number of MPPTs: Each MPPT can perform maximum power tracking independently, and multiple string connections can exist under the same MPPT. A larger number of MPPTs is more beneficial to solving the mismatch problem; a smaller number of MPPTs is more advantageous in terms of stability and efficiency.   Nominal power: The rated power of the device, the maximum value allowed for the operation of the device.   Power factor: Generally, the inverter outputs pure active power by default. That is, the power factor is 1. It can be set and adjusted according to the actual situation, and the power factor is ~1 (0.8 lead...0.8 lag). What is an IP rating? Ingress Protection: In the IEC standard, it is for the external protection of the electrical equipment enclosure. The first number of IPXX indicates dustproof; the second number indicates waterproof. The higher the number, the higher the level of protection. (For example: IP65 6 means completely preventing dust from entering, 5 means low-pres...

Looking at European energy storage from the German household storage market: maintaining cautious optimism According to EESA's forecast, the overall household savings scale in Europe in 2023 will be approximately 9.2GWh, and the German household savings market accounts for 47% of Europe's total scale, which has strong guiding significance. The cumulative installed capacity of energy storage in Germany will reach 7.4GW/11.5GWh in 2023, an increase of 3.5GW/5.3GWh from the end of 2022. The growth rate gradually slowed down in the second half of the year, from more than 200% in the middle of the year to -23% in December. In January 2024, Germany added 35.7MWh of large-scale storage capacity, 18.1MWh of industrial and commercial capacity, and 333.0MWh of household storage capacity; a total of 386.8MWh was added in the month, -10% year-on-year. The year-on-year growth rate is in a continuous downward trend, and has been negative for three consecutive months, confirming our previous cautious predictions for European energy storage. European electricity prices generally fall, and the impact of natural gas decreases According to TRADINGECONOMICS, the electricity prices of Germany, Italy, and the United Kingdom, the top three energy storage installed countries in Europe, are 68.54/95.75/61.00 euros/MWh respectively. Although there are certain price fluctuations on a monthly basis, they are at a lower level than the peak during the energy crisis in 2022. Low shock. The natural gas price index quoted $1.6822/MMBtu last Friday and will continue to trend downward after the year. In the short term, it will be difficult for European electricity prices to rise significantly. Energy storage subsidy policy maintains bottom line for household storage demand in Europe Fluctuations in European electricity prices determine the upper limit of energy storage demand, while the subsidy intensity and stability of European policies maintain the lower limit of energy storage demand. Taking Italy as an example, from February to April 2023, the government suspended the Superbonus subsidy plan due to deficit pressure, and reduced the Superbonus subsidy intensity in 2024 and 2025 after restarting, causing construction at thousands of construction sites to come to a standstill. In the end, the government had to extend the Superbonus scheme to a limited extent. It can be seen that the current European energy storage market demand is relatively fragile and highly dependent on policies. Current policy disturbances will become the core contradiction of European energy storage demand.

Off-Grid Solar Systems Self-Sufficient Energy Solutions Photovoltaic off-grid systems not only provide a way to disconnect from the traditional grid, but also bring new possibilities to users in remote areas or who want to reduce their dependence on the public grid. This article takes an in-depth look at how off-grid solar systems work, their key components, and how they can become an important part of modern sustainable energy solutions. 01. What is an off-grid solar system? Off-grid solar systems, as the name suggests, are independently operating solar systems that do not rely on the traditional power grid. The core components of these systems include solar panels, battery packs, battery management systems (BMS) and inverters. Solar panels are responsible for capturing sunlight and converting it into electrical energy, while batteries are used to store this electrical energy for use when the sun is low or at night. The charge controller ensures that the battery is charged and discharged in a safe and efficient manner, while the inverter converts the DC power stored in the battery into AC power that can be used in the home or business. Off-grid systems are particularly suitable for remote areas or for those who want to be more self-sufficient, providing a means of energy supply that is independent of the traditional grid. 02. Core components of off-grid solar systems When delving into off-grid solar systems, it’s crucial to understand their core components. In this article, we will focus on off-grid solar power plants. Small off-grid solar systems such as solar lamps and lawn lamps are beyond the scope of this article. Off-grid solar power plants are made up of several key parts, each playing an integral role. The following are the main components of an off-grid solar power plant: 1. Solar panels: The core of the power station, responsible for capturing solar energy and converting it into electricity. The quality, efficiency and quantity of battery panels directly determine the overall performance of the power station. 2. Battery Management System (BMS): BMS is a key component of the power station and is responsible for managing the current sent to the battery pack to prevent the battery from overcharging or over-discharging and ensuring the long-term health and efficiency of the battery pack. 3. Battery bank: used to store the energy generated by solar panels during the day for use when there is no sunlight or when demand is peak. The type, capacity and number of batteries will determine the energy storage capacity of the plant. 4. Inverter: Converts DC power stored in the battery into AC power that can be used in a home or business. 5. Bracket and mounting system: To maximize the efficiency of solar panels, a stable and appropriately angled bracket system is required to mount the solar panels. 6. Monitoring systems: Modern off-grid power plants often include smart monitoring systems to track the performance of the plant in real time and make a...