12V27A battery

　　How to set up a safe 12V27A battery protection circuit

　　According to statistics, the global demand for lithium-ion batteries has reached 1.3 billion, and with the continuous expansion of application fields, this data is increasing year by year. Because of this, with the rapid increase in the use of lithium-ion batteries in various industries, the safety performance of batteries has become increasingly prominent. Lithium-ion batteries are not only required to have excellent charge and discharge performance, but also have higher safety performance. So why do lithium batteries catch fire or even explode? Are there any measures to avoid and eliminate them?

　　The explosion of laptop batteries is not only related to the production process of the 12V27A battery cells used in them, but also to the battery protection board packaged in the battery, the charge and discharge management circuit of the laptop, and the heat dissipation design of the laptop. Unreasonable heat dissipation design and charge and discharge management of laptop computers will cause the battery cells to overheat, thereby greatly increasing the activity of the cells and increasing the chance of explosion and combustion.

　　Analysis on the composition and performance of 12V27A battery materials

　　First, let’s take a look at the material composition of lithium batteries. The performance of lithium-ion batteries mainly depends on the structure and performance of the internal materials used in the battery. The internal materials of these batteries include negative electrode materials, electrolytes, separators, positive electrode materials, etc.

　　Carbon materials are generally used as negative electrode materials, and the current development is relatively mature. The development of cathode materials has become an important factor restricting the further improvement of lithium-ion battery performance and the further reduction of prices. In current commercially produced lithium-ion batteries, the cost of cathode materials accounts for about 40% of the entire battery cost. The reduction in the price of cathode materials directly determines the reduction in the price of lithium-ion batteries. This is especially true for lithium-ion power batteries. For example, a small lithium-ion battery for a mobile phone only requires about 5 grams of cathode material, while a lithium-ion power battery used to drive a bus may require up to 500 kilograms of cathode material.

　　Although there are many types of cathode materials that can theoretically be used as lithium-ion batteries, the main component of the common cathode material is LiCoO2. When charging, the potential applied to the two poles of the battery forces the positive electrode compound to release lithium ions, and the molecules embedded in the negative electrode are arranged in a lamellar structure. of carbon. During discharge, lithium ions are precipitated from the carbon in the lamellar structure and recombine with the compound of the positive electrode. The movement of lithium ions creates an electric current. This is how lithium batteries work.

　　12V27A battery charge and discharge management design

　　When a 12V27A battery is charged, the potential applied to the two poles of the battery forces the compound in the positive electrode to release lithium ions and embed them in the carbon in the negative electrode, where the molecules are arranged in a lamellar structure. During discharge, lithium ions are precipitated from the carbon in the lamellar structure and recombine with the compound of the positive electrode. The movement of lithium ions creates an electric current. Although the principle is very simple, in actual industrial production, there are many more practical issues that need to be considered: the material of the positive electrode needs additives to maintain the activity of multiple charges and discharges, and the material of the negative electrode needs to be designed at the molecular structure level to accommodate more More lithium ions; the electrolyte filled between the positive and negative electrodes, in addition to maintaining stability, also needs to have good conductivity and reduce the internal resistance of the battery.

　　Although lithium-ion batteries have the advantages mentioned above, they have relatively high requirements for protection circuits. Overcharge and over-discharge should be strictly avoided during use, and the discharge current should not be too large. Generally speaking, the discharge rate It should not be greater than 0.2C. The charging process of 12V27A battery is shown in the figure. During a charging cycle, the lithium-ion battery needs to detect the voltage and temperature of the battery before charging begins to determine whether it can be charged. Charging is prohibited if the battery voltage or temperature exceeds the range allowed by the manufacturer. The allowed charging voltage range is: 2.5V~4.2V per battery.

　　When the battery is in deep discharge, the charger must be required to have a precharge process so that the battery can meet the conditions for fast charging; then, according to the fast charging speed recommended by the battery manufacturer, which is generally 1C, the charger performs constant current charging on the battery. The battery voltage rises slowly; once the battery voltage reaches the set termination voltage (usually 4.1V or 4.2V), the constant current charging is terminated, the charging current rapidly decays, and the charging enters the full charge process; during the full charge process, the charging current gradually Decay until the charging rate drops below C/10 or the full charge time times out, then it switches to top cutoff charging; when top cutoff charging occurs, the charger replenishes energy for the battery with a very small charging current. After the top stops charging for a period of time, the charging is turned off.

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