Lithium Battery PCB vs Lithium Battery BMS

By Gerald, Updated on April 11, 2024

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Welcome to our insightful discussion on the differences between lithium battery PCB and lithium battery BMS! In the realm of lithium battery technology, these two components play crucial roles in ensuring safety, performance, and reliability. Understanding the distinctions between lithium battery PCB and lithium battery BMS is essential for making informed decisions when designing or selecting battery systems.

Part 1. What is the lithium battery protection board (PCB)?

Lithium-ion batteries are most afraid of over-charging and over-discharge during use. Overcharging means that the charging voltage exceeds the upper limit voltage. When a lithium battery is overcharged, a large amount of gas will be produced, causing the internal pressure to rise rapidly and the battery to explode. Over-discharge means the discharge cut-off voltage is lower than the lower limit voltage. Over-discharge of lithium batteries will reduce the capacity of the top layer, shorten the battery life, and directly damage the battery, causing it to be scrapped.

Therefore, the lithium battery protection board‘s most basic protection of lithium batteries is overcharge and over-discharge protection.

The lithium battery protection board is a core component of the intelligent management system for lithium-ion batteries. Its main functions include overcharge protection, over-discharge protection, over-temperature protection, over-current protection, etc., to ensure the safe use of the battery and extend its service life.

Part 2. Principle of lithium battery protection board (PCB)

Lithium battery protection boards usually contain microcontrollers, MOS tubes, resistors, capacitors, and other electronic components. Its working principle is based on real-time monitoring and control of battery voltage, current, and other parameters. When the voltage and current of the battery exceed or fall below the set threshold, the microcontroller will send a control signal to turn the MOS tube on or off, thereby controlling the charge and discharge of the battery.

Part 3. Main functions of lithium battery protection board (PCB)

To ensure the safety of lithium batteries, there are many requirements for lithium battery protection boards (PCB), such as:

Basic protection: overcharge protection, over-discharge protection.
Enhanced protection: overcurrent protection, high-temperature protection, low-temperature protection, short circuit protection, reverse connection protection.
Extended protection: good consistency, small pressure difference, small temperature difference.

Of course, lithium batteries do not necessarily require all the above protection functions. The lithium battery protection board on the scene requires the following functions:

1. Overcharge protection
When the lithium battery is charged to the set voltage, the battery protection board will automatically cut off the charging circuit to prevent the lithium battery from overcharging.

2. Over-discharge protection
When the lithium battery is discharged to the set voltage, the lithium battery protection board will automatically cut off the discharge circuit to prevent the lithium battery from over-discharging.

3. Over-temperature protection
When the lithium battery temperature is too high or too low, the lithium battery protection board will automatically cut off the charge and discharge circuit to prevent the lithium battery from being damaged due to abnormal temperature.

4. Overcurrent protection
When the charging and discharging current of the lithium battery is too large, the lithium battery protection board will automatically cut off the charging and discharging circuit to prevent the lithium battery from being damaged due to excessive current.

Due to the material characteristics of the lithium battery itself, it cannot be overcharged, over-discharged, overcurrent, short-circuited, or charged and discharged at ultra-high and low temperatures. Therefore, lithium batteries always require a protection circuit board.

Part 4. Types of lithium battery PCB

Hardware-type lithium battery PCB can be divided into an independent port protection circuit board and a common port (same port) protection circuit board.

Independent port protection circuit board: There are three ports in total (charging port, discharge port, common terminal); that is, the charging and discharging ports are separate. (Refer to the picture on the left) There are two ports, CH+ and CH-, for charging and two ports, P+ and P-, for discharging.

Public port (same port) protection circuit board: There are two ports (positive and negative ports), one for charging and discharging. (Refer to the picture on the right) There are two ports for charging, CH+ (P+) and CH- (P-), and two ports for discharging, CH+ (P+) and CH- (P-).

Part 5. What is lithium battery BMS (battery management system)?

Lithium battery BMS is mainly used to intelligently manage and maintain each battery unit, prevent overcharge and over-discharge of lithium batteries, extend the service life of lithium batteries, and monitor the status of lithium batteries.

Lithium battery After BMS solves the safety problem of lithium batteries, BMS has many additional functional requirements based on different usage environments and usage occasions, such as

Communication function: Users need to know the operating status of the battery PACK, such as RS232/RS485/CAN, etc.;
Calculation function: BMS can calculate SOC (State of Charge)/estimate SOH (State of Health);
Warning function: BMS needs to inform users of battery problems;
Recording function: BMS needs to record the historical operating data of the battery PACK, including historical alarm data;
Fault diagnosis function: PCB or BMS itself can diagnose problems by itself;
Display function: Users can directly read information and set parameters through the display screen;
Other functions include the balancing function, thermal management function, etc.

Part 6. Lithium battery BMS principle

Lithium battery BMS includes control IC, MOS switch, fuse Fuse, NTC thermistor, TVS transient voltage suppressor, capacitor and memory, etc.

In the picture above, the control IC turns the circuit on and off by controlling the MOS switch to protect it. FUSE implements secondary protection on this basis. TH is temperature detection, and there is a 10K NTC inside. NTC mainly implements temperature detection. TVS mainly suppresses surges.

Part 7. What is the use of lithium battery BMS (battery management system)?

Lithium battery BMS can realize data collection, control, transmission, and other functions.

1. Sensing and measuring: Measuring means sensing the status of the battery

This is the basic function of BMS, including the measurement and calculation of some indicator parameters, including voltage, current, temperature, electricity, SOC (state of charge), SOH (state of health), SOP (state of power), SOE (state of energy).

2. Alarm and protection

When an abnormality occurs in the battery, the BMS can alert the platform to protect the battery and take corresponding measures. At the same time, abnormal alarm information will be sent to the monitoring and management platform, and alarm information for different levels will be generated.

For example, when the temperature is overheated, the BMS will directly disconnect the charge and discharge circuit, perform overheat protection, and send an alarm to the background.

Lithium batteries will mainly issue warnings for the following issues:

Overcharge: single unit overvoltage, total voltage overvoltage, charging overcurrent;
Over-discharge: single unit Undervoltage, total voltage Undervoltage, discharge overcurrent;
Temperature: cell temperature is too high, ambient temperature is too high, MOS temperature is too high, battery core temperature is too low, ambient temperature is too low;
Status: water immersion, collision, inversion, etc.

3. Balanced management

The need for balanced management arises from the inconsistency in battery production and use.

From a production perspective, each battery has its life cycle and characteristics, and no two batteries are the same. Due to inconsistencies in materials such as separators, cathodes, and anodes, the capacities of different batteries cannot be completely consistent. For example, the consistency indicators of the voltage difference, internal resistance, etc., of each battery cell that makes up a 48V/20AH battery pack vary within a certain range.

From a usage perspective, the electrochemical reaction process can never be consistent during battery charging and discharging. Even if it is the same battery pack, the battery charge and discharge capacity will differ due to different temperatures and collision degrees, resulting in inconsistent battery cell capacities.

Therefore, the battery needs both passive balancing and active balancing. A pair of thresholds for starting and ending equalization are set. For example, in a group of batteries, equalization starts when the difference between the extreme voltage of a single cell and the average voltage of the group reaches 50mV and ends at 5mV.

4. Communication and positioning

BMS has a separate communication module, which is used for data transmission and battery positioning, respectively. In real time, BMS can transmit the relevant data sensed and measured to the operation management platform.

Part 8. Lithium battery protection board (PCB) vs BMS

Lithium battery protection board and lithium battery BMS both protect lithium batteries. The difference between them is:

The lithium battery protection board comprises IC, MOS tube, resistor, and capacitor components. It is an important component of the lithium battery.
The lithium battery BMS can be edited and comes with battery management software, which is relatively smarter. The BMS is equivalent to the brain of the lithium battery and plays a management and control role.
Lithium battery protection boards play an important role in consumer lithium battery and power battery fields. BMS is used in the field of power batteries.
The battery management system operates better than the battery protection board. However, the performance of the BMS is unstable at low temperatures.

Part 9. Summary

In summary, this article has provided a comprehensive comparison between lithium battery PCB and lithium battery BMS. While lithium battery PCB focuses on protecting individual cells and regulating charging and discharging processes, lithium battery BMS provides comprehensive monitoring and control of the entire battery pack, ensuring optimal performance and safety. By understanding the differences between lithium battery PCB and lithium battery BMS, battery system designers and users can make informed decisions to meet their specific requirements and achieve the desired balance between performance, safety, and reliability.

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