The principle of lithium iron phosphate battery protection board, the parameters of lithium battery protection board. The lithium battery protection board is to protect the charging and discharging of the series-connected lithium battery pack, and the lithium iron phosphate battery protection board is a necessary equipment to enhance the safety of the power lithium-ion battery. 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. The lithium battery must be used together with the protection board to ensure the safety and reliability of the entire system.

Principle of lithium iron phosphate battery protection board

The reason why the lithium iron phosphate battery (rechargeable type) needs protection is determined by its own characteristics. Because 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 iron phosphate battery will always appear with an exquisite 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 lithium iron phosphate 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.

1. Overcharge detection voltage: Under normal conditions, Vdd gradually increases to the voltage between VDD and VSS when the CO terminal changes from high level to low level.

2. Overcharge release voltage: In the charging state, Vdd gradually decreases to the voltage between VDD and VSS when the CO terminal changes from low level to high level.

3. Overdischarge detection voltage: Under normal conditions, Vdd gradually decreases to the voltage between VDD and VSS when the DO terminal changes from high level to low level.

4. Overdischarge release voltage: In the overdischarge state, Vdd gradually rises to the voltage between VDD and VSS when the DO terminal changes from low level to high level.

5. Overcurrent 1 detection voltage: In the normal state, VM gradually rises to the voltage between VM and VSS when DO changes from high level to low level.

6. Overcurrent 2 detection voltage: In the normal state, VM rises from OV to the voltage between VM and VSS when the DO terminal changes from a high level to a low level at a speed of 1ms or more and 4ms or less.

7. Load short-circuit detection voltage: In the normal state, VM starts from OV and rises to the voltage between VM and VSS when the DO terminal changes from high to low at a speed of 1μS or more and 50μS or less.

8. Charger detection voltage: In the over-discharge state, VM gradually decreases with OV to the voltage between VM and VSS when DO changes from low level to high level.

9. Current consumption during normal operation: Under normal conditions, the current flowing through the VDD terminal (IDD) is the current consumption during normal operation.

10. Over-discharge current consumption: In the discharge state, the current (IDD) flowing through the VDD terminal is the over-current discharge current consumption.

Do I need a protection board for lithium iron phosphate batteries?

The lithium iron phosphate battery pack protection board is necessary and useful. The lithium protection board has functions such as battery pack over-discharge protection, over-charge protection, over-current protection, and short-circuit protection. 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 protection board circuit can separately detect the voltage and current of each battery in the series-connected lithium iron phosphate battery pack, and control the charging and discharging process of the 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.

The power lithium iron phosphate battery protection board is a necessary equipment to enhance the safety of power lithium ion batteries. 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.

Introduction to the main parameters of lithium battery protection board

The main technical parameters of the lithium battery protection board include overcharge protection, overdischarge protection, overcurrent protection, short circuit protection, temperature protection, internal resistance, power consumption, etc.

Overcharge protection: overcharge detection voltage, overcharge detection delay time, overcharge release voltage

Over-discharge protection: over-discharge detection voltage, over-discharge detection delay time, over-discharge release voltage

Overcurrent protection: charge overcurrent protection current, charge overcurrent detection delay time, charge overcurrent release delay time, discharge overcurrent protection current, discharge overcurrent detection delay time, discharge overcurrent release delay time

Short-circuit protection: protection conditions, external circuit short-circuit, detection delay time, protection release delay time

Temperature protection: temperature protection conditions

Temperature protection: protection release condition

Internal resistance: main circuit on-resistance

Power consumption: current consumption when the circuit is sleeping, current consumption when the circuit is working

Technical indicators of lithium iron lifepo4 battery protection board

1. Voltage protection capability

Overcharge protection: The lithium iron lifepo4 battery protection board must have the ability to prevent the cell voltage from exceeding the preset value. Over-discharge protection: The protection board must have the ability to prevent the cell voltage from falling below the preset value.

2. Current capability (over-current protection current, short-circuit protection)

As a safety protection device for lithium batteries, the protection board must not only work reliably within the normal operating current range of the equipment, but also quickly act when the battery is accidentally short-circuited or over-current, so that the batteries are protected.

3. On-resistance

Definition: When the charging current is 500mA, the on-resistance of the MOS tube. Due to the high operating frequency of communication equipment, the low bit error rate required for data transmission, and the steep rising and falling edges of the pulse train, the current output capability and voltage stability of the battery are required to be high, so the MOS switch of the protection board is turned on The time resistance should be small. The single-cell battery protection board is usually less than 70mΩ. If it is too large, it will cause the communication equipment to work abnormally, such as the sudden disconnection of the mobile phone during a call, the phone cannot be connected, noise, etc.

4. Self-consumption current

Definition: The working voltage of the IC is 3.6V. Under no-load conditions, the working current flowing through the protection IC is generally very small. The self-consumption current of the protection board directly affects the standby time of the battery. It is usually specified that the self-consumption current of the BMS is less than 10 microamperes

5. Mechanical properties, temperature adaptability, antistatic ability

The lithium iron lifepo4 battery protection board must be able to pass the vibration and impact tests specified by the national standard; the BMS can work safely at -40 to 85 degrees, and can withstand the non-contact ESD electrostatic test of ±15KV

The lithium iron lifepo4 battery BMS has the function of protecting the battery and avoiding battery overcharging. When the external power supply continues to quickly charge the battery, the lithium battery protection board will have a protective effect. When the internal power of the lithium battery reaches the saturation level, the internal circuit of the lithium battery protection board will automatically cut off the external fast charging power supply. Because the parameters of lithium batteries are also different, the types of corresponding protection boards are also different. The lithium iron phosphate battery protection board must be used accordingly.