polymer lithium battery

　　The principle of balanced charging of polymer lithium battery pack protection board, what types of polymer lithium battery pack balanced charging circuits are divided into

　　The principle of equalizing charging of polymer lithium battery pack protection board. What are the categories of equalizing charging circuits for polymer lithium battery packs? Commonly used balancing charging technologies include constant shunt resistor balancing charging, on-off shunt resistor balancing charging, average battery voltage balancing charging, switched capacitor balancing charging, buck converter balancing charging, inductor balancing charging, etc. When charging a group of lithium batteries in series, each battery should be charged evenly, otherwise the performance and life of the entire group of lithium batteries will be affected during use.

　　Balanced charging principle of polymer lithium battery pack protection board

　　When the polymer lithium battery pack is charging, the positive and negative poles of the external power supply of the polymer lithium battery pack protection board are connected to the positive and negative terminals BAT+ and BAT- of the battery pack respectively. The charging current flows through the positive electrode BAT+ of the battery pack and the single polymer lithium battery 1~N in the battery pack. , discharge control switching device, charging control switching device, polymer lithium battery pack protection plate negative electrode BAT-.

　　The charging overvoltage protection control signal of the single-cell polymer lithium battery protection chip in the control circuit part of the polymer lithium battery pack protection board system is isolated by an optical coupler and output in parallel to provide the gate voltage for the conduction of the charging switch device in the main circuit;

　　If one or several lithium batteries enter the overvoltage protection state first during the charging process, the overvoltage protection signal controls the discharge of the shunt discharge branch connected in parallel at the positive and negative ends of the single polymer lithium battery. The corresponding single polymer lithium battery in the circuit is disconnected from the charging circuit.

　　While charging protection, the polymer lithium battery pack protection board system uses the protection chip to control the on and off of the shunt discharge branch switching device to achieve balanced charging. This solution is different from the traditional approach of achieving balanced charging at the charger end and reduces the cost of lithium batteries. Cost of pack charger design and application.

　　polymer lithium battery protection plate electrical balancing function

　　1. When the battery voltage of each battery in the battery pack is different due to battery matching or external environmental influences, if the battery voltage difference between the series connected groups exceeds the set value, the balancing circuit is allowed to operate, and the balancing is started during the charging process. The balancing resistor discharges the battery pack with the highest relative capacity, and the balancing current is the balanced absorption current value, thereby reducing the battery pack voltage rise rate.

　　2. When the voltage difference of each group of batteries connected in series is less than the set value, the balancing circuit is prohibited from working and there is no balancing power.

　　What are the categories of polymer lithium battery pack balancing charging circuits?

　　For the design of battery pack balancing charging circuit topology, domestic and foreign researchers have proposed many different circuit topologies. Based on the energy consumption of the circuit during the balancing process, the battery pack balancing charging circuit can be divided into two categories: energy dissipative type and energy non-dissipating type.

　　1. Energy dissipation type balancing is achieved by discharging shunt resistors in parallel at both ends of each single cell in the battery pack, thereby achieving balancing. The shunt resistor discharge balancing circuit is the most direct balancing technology. This technology discharges single cells with high capacity through shunt resistors until the capacities of all single cells are at the same level.

　　2. Compared with energy dissipative balancing, energy non-dissipative balancing circuits consume less energy but have a more complex circuit structure.

　　① Feidu capacitor generator connects each battery to a capacitor in parallel. By switching this capacitor, it can be connected in parallel to its own battery or to an adjacent battery. When the voltage of a certain battery is too high, first connect the capacitor in parallel with the battery so that the capacitor voltage is consistent with the battery, then switch the capacitor to the adjacent battery, and the capacitor discharges the battery to achieve energy transfer.

　　②Switched capacitor method balancing For a power battery pack composed of n single cells connected in series, the switched capacitor method balancing circuit requires n-1 capacitive elements and 2n switching devices. Taking the inconsistent voltages of single cells B1 and B2 as an example, there are two states during the control process. The disadvantage of this circuit is that it can only be used to balance the terminal voltages between single cells, and can only achieve balance between adjacent single cells. The energy flows, so when the number of batteries in series is large, the equilibrium time is relatively long.

　　③The double-layer capacitor method balancing circuit is also a derivation and transformation of the switched capacitor method circuit. The difference is that this circuit uses two layers of switched capacitors to realize energy transfer between batteries. Compared with the switched capacitor balancing circuit, the advantage of this circuit is that it uses the increased outer switching capacitance, so that the single cell can not only balance the voltage with adjacent single cells, but also with non-adjacent single cells. , so the equilibrium speed is improved.

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