What are the functions of the battery aaa alkaline management system?

　　battery aaa alkaline management system design scheme

　　Abstract: This article discusses the design of a power lithium battery management system to achieve overcharge protection, overdischarge protection, overcurrent protection and balanced charging functions for lithium battery power battery packs.

　　1 Function of protection circuit

　　1.1 Overcharge protection

　　For lithium-ion batteries, the maximum voltage of a single cell after charging must not exceed the specified value. Otherwise, the electrolyte in the battery will be decomposed, causing the temperature to rise and generate gas, which will reduce the service life of the cell and even cause an explosion in severe cases. , so the protection circuit must ensure that there is absolutely no overcharging. The terminal voltage of each battery in the battery pack must be monitored. When the voltage of the cell exceeds the set value, the overcharge protection function is activated, and the protection circuit cuts off charging. loop to stop charging. Protection can be stopped only when the cell voltage returns to the allowable voltage and the overcharge lock mode is released. Lithium-ion batteries made of different materials have different specified values for their protection voltage and release voltage.

　　In addition, attention must also be paid to malfunctions caused by noise. In order to prevent misjudgments and misoperations, an overcharge protection delay must be set, and the delay time cannot be shorter than the duration of the noise. When the voltage continues to exceed the overcharge detection voltage for a certain period of time, the overcharge protection will be triggered.

　　1.2 Over-discharge protection

　　Excessive discharge of lithium-ion batteries will also shorten their service life, and the damage to the battery is often irreversible. In order to prevent the over-discharge state of the lithium-ion battery, when the lithium-ion battery voltage is lower than its over-discharge voltage detection point, the over-discharge protection is activated, the discharge is stopped, and the battery is kept in a low quiescent current standby mode. The parameter settings are similar to the over-discharge detection point. Charge protection.

　　1.3 Overcurrent/short circuit protection

　　The maximum discharge current of lithium-ion batteries has a certain limit. Excessive discharge current will also cause irreversible damage to the lithium battery and affect its service life.

　　The function of short-circuit protection is actually an extension of over-current protection. If a large current is discharged due to external short circuit or other reasons, the discharge must be stopped immediately, otherwise it may cause serious damage to the lithium battery itself and external equipment.

　　1.4 Battery balancing

　　Power lithium-ion batteries generally require several, dozens or even hundreds of strings. During the production process of the battery, there are many processes from coating to finished product. Even after strict testing procedures, each set of power supply The voltage, resistance, and capacity of the battery are consistent, but after a period of use, the internal resistance, voltage, capacity and other parameters of the battery fluctuate, forming an inconsistent state, which will produce differences in one way or another. This difference is reflected in the different voltages between series-connected battery cells when the battery pack is fully charged or discharged. In this case, during the charging process of the battery pack, the battery cells with too high voltage trigger the overcharge protection of the battery pack early, while the battery cells with too low voltage during the discharge process cause the over-discharge protection of the battery pack, thereby reducing the overall health of the battery pack. The capacity is significantly reduced. The capacity reflected by the entire battery pack is the capacity of the worst-performing battery cell in the battery pack. Overcharge and over-discharge are easy to occur during use and are difficult to detect, leading to premature failure. Therefore, the protection circuit is required to complete the balancing operation of the battery unit to draw excess current from the battery with a higher voltage, consume excess power, achieve battery balancing, maximize the effectiveness of the power lithium battery, and extend the service life of the battery. , increase safety. Currently commonly used balancing methods include energy storage balancing and resistance balancing.

　　2.1IC control

　　Currently, there are many chips that can realize the protection function of lithium-ion batteries. There are many kinds of chips to choose from abroad, Taiwan, and mainland China. Currently, Japanese Ricoh and Seiko solutions are used more. The solutions are mature and the peripheral circuits are simple, but the price is relatively expensive.

　　The functions implemented by various protection ICs are almost the same, and their protection modes and external circuits are also similar. In practical applications, different ICs can be selected according to needs. When choosing an IC, you need to consider many factors. The overcharge protection voltage of different types of ICs is different, including 4.25V and 4.35V. There are also the IC's own power consumption, whether the peripheral circuit is simple enough, and whether the parameters of the protection IC are accurate. Compliance with the requirements and whether the volume is small enough must be carefully considered.

　　2.2 MCU controls some existing integrated circuit protection chips mainly for the protection of battery packs with less than 4 cells. For battery packs with more than 4 cells, multiple single-level protection chips can be connected in series or several multi-level protection can be used. The way chips are connected in series. However, this circuit that uses multiple protection chips connected in series to protect battery packs with more than 4 cells has poor scalability. At the same time, integrated protection chips often only target the characteristics of one type or type of battery, lack flexibility, and are often relatively expensive. For this reason, combined with the charging and discharging characteristics of lithium-ion power batteries, battery aaa alkaline protection circuits in many cases adopt design solutions with MCU (microprocessor) as the core.

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