Principle of lifepo4 battery protection board, lithium battery protection board program. Some people say that lithium iron phosphate batteries are good, why use a protective plate. I don't want to talk about the shortcomings of lithium iron phosphate batteries, but if the protection board does not work, the lithium iron phosphate batteries cannot be used. The lifepo4 battery pack protection board is necessary and useful. The protection board circuit can separately detect the voltage and current of each battery in the series battery pack, and control the charging and discharging process of the battery pack. Lithium battery protection boards have different circuits and parameters depending on the IC, voltage, etc. used.

Principle of lifepo4 battery protection board

The reason why the lifepo4 battery (rechargeable type) needs protection is determined by its own characteristics. Since the material of the lithium battery itself determines that it cannot be overcharged, overdischarged, overcurrent, short circuited, and ultra-high temperature charging and discharging, the lithium battery components of the lithium battery will always appear with a delicate protection board and a current fuse.

The protection function of lithium battery is usually completed by a protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage of the battery cell and the charging and discharging circuit at all times under the environment of -40°C to +85°C. Current, timely control the on and off of the current loop; PTC prevents severe damage to the battery in high temperature environments.

Ordinary lifepo4 battery protection board usually includes control IC, MOS switch, resistor, capacitor and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to turn on under all normal conditions to make the cell and the external circuit conduct, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the cell’s Safety.

Do lithium iron phosphate batteries need a protective plate?

The lifepo4 battery has a single voltage of 3.2V and is now generally used as a power source for electric vehicles. Lithium iron phosphate batteries for electric vehicles are composed of many single cells in series or in parallel to achieve different voltage and capacity levels. Due to the discrete nature of the battery, after a period of use, the voltage of each battery will become more and more different, some are higher than 3.2V, and some are lower than 3.2V. This has a great impact on the entire battery pack, and the overall capacity becomes smaller. The life span is shortened.

The lifepo4 battery protection board circuit can separately detect the voltage and current of each battery in the series battery pack, and control the charging and discharging process of the lithium battery pack. The voltage of each battery in the battery pack is between the overcharge detection voltage and the overdischarge detection voltage, and when the output is not short-circuited, the MOS tube is turned on, P+ and P- output the battery pack voltage, allowing the battery pack to charge and discharge . In addition, the protection board also has functions such as battery pack over-discharge protection, over-charge protection, over-current protection, and short-circuit protection.

In most cases, the lithium battery protection board should have the function of controlling the working conditions of the lithium-ion battery. These working conditions include voltage, current, temperature, etc. Due to the particularity of the use of lithium-ion batteries, the power lithium-ion battery must be used together with the protection board to ensure the safety and reliability of the entire system.

Lithium battery protection board solution

Due to the characteristics of the lifepo4 battery, it is necessary to protect the charging and discharging process in the application to avoid overcharging, overdischarging or overheating, so as to ensure the safe operation of the battery. In recent years, there has been a trend in the industry to package several chips together to improve integration and reduce the area of the final solution. The lithium battery protection market is no exception. The two lithium battery protection schemes A and B in Figure 3 seem to integrate the two chips in Figure 2 into one chip, but in fact, the internal controller IC and switch tube chip in the package are still separated from different sources. Of manufacturers, the solution is only to seal the two together, commonly known as "two cores in one".

In recent years, many newly created switch tube chip manufacturers have appeared on the market. In order to reduce the cost, the original gold wire was changed to copper wire during packaging, and the switch tube does not have ESD protection. Although these products have a certain difference in performance compared with brand switching tubes, they quickly seized the secondary market because of their cost advantages. This is also the reason why traditional solutions compete with the "two-core in one" and positive electrode protection solutions in the market. Winning made a huge contribution.

Based on the design scheme of the equalization charging protection board for lithium iron phosphate battery packs, commonly used equalization charging techniques include constant shunt resistance equalization charging, on-off shunt resistance equalization charging, average battery voltage equalization charging, switched capacitor equalization charging, and step-down converter equalization Charging, inductance equalizing charging, etc.

When a group of lithium iron phosphate batteries are charged in series, each battery should be balanced and charged, otherwise the performance and life of the entire group of batteries will be affected during use. However, the existing single-cell lithium battery protection chips do not have a balanced charge control function. The balanced charge control function of a multi-cell lithium battery protection chip requires an external CPU; it is realized through serial communication with the protection chip (such as I2C bus). The complexity and design difficulty of the protection circuit are reduced, the efficiency and reliability of the system are reduced, and the power consumption is increased.

Lithium iron phosphate batteries still need a protection board. When charging a group of lithium batteries in series, ensure that each battery is charged in a balanced manner, otherwise the performance and life of the entire group of batteries will be affected during use.