Disadvantages of Lithium Battery Protection Circuits -Lithium - Ion Battery Equipment
In practical applications, due to the difference between lithium-ion batteries, after a period of charging and discharging, it is found that the upper and lower voltages of a single battery are uneven, which seriously affects the function of the system. In view of this situation, the concepts of upper balance and lower balance are proposed, and the upper and lower balance circuits of Li-ion batteries are studied in detail. The experimental results show that the balance circuit planning of several lithium-ion batteries is correct, which lays a solid foundation for the research of high-performance hybrid power system.(Lithium - Ion Battery Equipment)
NiMH batteries are alkaline batteries. Since the cell voltage is relatively low, there is a recall effect, and a large number of discharges must be scheduled, which greatly increases the task of the power management system. Secondly, the self-discharge rate is high (10%~15%).
Compared with other batteries, lithium-ion batteries have high power density (800w/kg), high cell voltage (unified voltage 3.6V), no pollution, low self-discharge rate (about 3%~5%), and no memory effect. It has the characteristics of a kind of ambition power battery, so it is widely used in mobile power supply, hybrid electric car, backup power low-voltage switchgear and flight space battery equipment.
1. The deficiencies of the existing lithium-ion battery protection circuit in my country
The average voltage of lithium-ion batteries is only 3.6V, and the discharge current is also required. In order to improve the current and voltage level of the system, in some dynamic situations, lithium-ion batteries with high current and high voltage are usually used in parallel and then in series as the power system. Since lithium-ion batteries are very sensitive to voltage, a certain protection circuit is generally added to the battery pack during use.
2. Improved lithium-ion battery protection circuit principle
The equalization circuit refers to a person participating in the hardware circuit, which can make the upper limit voltage between the entire battery cells or maintain a consistent lower voltage, effectively protect the upper limit of the battery charging voltage and the lower limit of the discharge voltage, and fundamentally reduce the battery The impact system then arrives to improve cellular function and extend battery life. It contains two kinds of circuits: an upper balance circuit and a lower balance circuit.
Two sets of power systems in this paper are planned for hybrid electric vehicles: 3-series lithium-ion battery protection system (maximum voltage of 12.75v, uniform discharge voltage of 10.8v) and 10-series lithium-ion battery protection system (maximum voltage of 42.5v, uniform discharge voltage) The discharge voltage is 36v), and the discharge current is 10 and 40 respectively. The system principle is shown in Figure 1, that is, on the basis of its basic protection circuit (overvoltage/undervoltage/overtemperature/overcurrent/short circuit protection), it involves upper and lower equalization circuits.
2.1TL431 balance circuit
In this paper, the upper balance circuit is designed according to its characteristics, as shown in Figure 2. Adjust the resistance values of R1, R2, and R3. When the power supply voltage exceeds the set value, register TL431, and reduce the battery voltage through the power resistance R* energy dissipation to reach the fixed point (equilibrium point). According to the experimental results of the balance circuit of domestic electric vehicles and electric motorcycles, when the balance point is 4.20v, the resistance values are: R1=68k! R2=100k!, R3=4.3k!.
NiMH batteries are alkaline batteries. Since the cell voltage is relatively low, there is a recall effect, and a large number of discharges must be scheduled, which greatly increases the task of the power management system. Secondly, the self-discharge rate is high (10%~15%).
Compared with other batteries, lithium-ion batteries have high power density (800w/kg), high cell voltage (unified voltage 3.6V), no pollution, low self-discharge rate (about 3%~5%), and no memory effect. It has the characteristics of a kind of ambition power battery, so it is widely used in mobile power supply, hybrid electric car, backup power low-voltage switchgear and flight space battery equipment.
1. The deficiencies of the existing lithium-ion battery protection circuit in my country
The average voltage of lithium-ion batteries is only 3.6V, and the discharge current is also required. In order to improve the current and voltage level of the system, in some dynamic situations, lithium-ion batteries with high current and high voltage are usually used in parallel and then in series as the power system. Since lithium-ion batteries are very sensitive to voltage, a certain protection circuit is generally added to the battery pack during use.
2. Improved lithium-ion battery protection circuit principle
The equalization circuit refers to a person participating in the hardware circuit, which can make the upper limit voltage between the entire battery cells or maintain a consistent lower voltage, effectively protect the upper limit of the battery charging voltage and the lower limit of the discharge voltage, and fundamentally reduce the battery The impact system then arrives to improve cellular function and extend battery life. It contains two kinds of circuits: an upper balance circuit and a lower balance circuit.
Two sets of power systems in this paper are planned for hybrid electric vehicles: 3-series lithium-ion battery protection system (maximum voltage of 12.75v, uniform discharge voltage of 10.8v) and 10-series lithium-ion battery protection system (maximum voltage of 42.5v, uniform discharge voltage) The discharge voltage is 36v), and the discharge current is 10 and 40 respectively. The system principle is shown in Figure 1, that is, on the basis of its basic protection circuit (overvoltage/undervoltage/overtemperature/overcurrent/short circuit protection), it involves upper and lower equalization circuits.
2.1TL431 balance circuit
In this paper, the upper balance circuit is designed according to its characteristics, as shown in Figure 2. Adjust the resistance values of R1, R2, and R3. When the power supply voltage exceeds the set value, register TL431, and reduce the battery voltage through the power resistance R* energy dissipation to reach the fixed point (equilibrium point). According to the experimental results of the balance circuit of domestic electric vehicles and electric motorcycles, when the balance point is 4.20v, the resistance values are: R1=68k! R2=100k!, R3=4.3k!.
