Battery PCB – What you need to know

 

Introduction

Battery Protection Circuit Boards (PCBs) play a vital role in ensuring the safety, efficiency, and longevity of rechargeable batteries used in a wide range of electronic devices. As the demand for portable gadgets and electric vehicles increases, the need for reliable and robust battery management systems becomes even more critical.

The Battery Protection Circuit Board, often termed the Battery Management System (BMS), is a critical component in rechargeable battery packs that play a pivotal role in ensuring the safe and efficient operation of various electronic devices. As the demand for portable gadgets, electric vehicles, and renewable energy storage systems grows, the significance of Battery PCBs becomes increasingly evident. These intelligent electronic controllers are designed to monitor and regulate key parameters of the battery, including voltage, current, and temperature. By doing so, they protect against potential hazards like overcharging, over-discharging, short circuits, and overheating, which can lead to catastrophic failures and pose serious safety risks. The Battery PCB’s ability to safeguard batteries and optimize their performance is crucial for enhancing user experience, prolonging battery life, and contributing to a sustainable future by reducing electronic waste.

In this article, we will delve into the world of Battery PCBs, exploring their functions, components, design considerations, and the role they play in safeguarding our devices and the environment.

Lithium Battery Pack with PCB
Lithium Battery Pack with PCB

 

What is a Battery Protection Circuit Board (PCB)?

A Battery Protection Circuit Board, often referred to as a Battery Management System (BMS), is an essential component in rechargeable battery packs. It acts as an intelligent electronic controller that monitors and regulates various parameters to ensure the safe and efficient operation of the battery. The primary functions of a Battery PCB include:

4 Cell Li-ion BMS
4 Cell Li-ion BMS

 

Voltage Protection

The battery is protected for both High voltages and low voltages. It can be viewed below in the figure, the upper threshold is roughly 3.5V for a single cell and it would be cut off from supply when the limit is reached. Similarly, an action can be taken when the voltage levels are below its safe voltage threshold. It can lead to various issues like accelerated aging and reduced capacity. The BMS performs voltage monitoring and current monitoring using DW01 or similar ICs.

Current Limits For Li-ion Batteries
Current Limits For Li-ion Batteries

 

Current Protection

This feature ensures that the battery functionality during too much loading and short circuit. Normally, in case of a short circuit load is disconnected from the entire circuitry. Once the fault condition is fixed BMS continues the normal operation. Normally, in BMS current and voltage protection are ensured by using MCU that are processing real-time data using shunt resistors or independent ICs that are responsible for the operation. The overcurrent protection for a single Li-ion battery used by a BMS is almost 150mV. This voltage level is entirely dependent upon the sense Resistor value.

DW01 Single Li-ion cell controller IC limit specifications
DW01 Single Li-ion cell controller IC limit specifications

 

Short Circuit Protection

DW01 continuously monitors current at every instant using voltage sense at the shunt pin shown in figure below. A short circuit occurs when there is an unintended direct connection between the positive and negative terminals of the battery, resulting in a sudden surge of current. This can lead to rapid and uncontrollable current flow, overheating, and potentially dangerous situations, such as fire or explosion.

Temperature Monitoring

Temperature is a crucial parameter that significantly impacts the performance, efficiency, and safety of battery packs. Typically it incorporates temperature sensors, such as thermistors or integrated temperature sensors, which are strategically placed in or near the battery cells. These sensors measure the temperature and provide real-time data to the main controller. If the battery temperature exceeds a predefined threshold, the BMS activates safety measures to protect the battery and the connected devices. It might reduce the charging or discharging rate to lower the temperature, or in extreme cases, shut down the battery to prevent any potential hazards. In addition, temperature monitoring helps in estimating the State of Health of the battery, which refers to its overall health and capacity. High temperatures can accelerate battery aging, and by tracking the temperature over time, the BMS can assess the battery’s condition and predict its remaining useful life. Generally, BMS operates in safe operating ranges from 0°C to 45°C. Beyond that limits, the temperature monitoring system operates and disrupts the operation.

Temperature Limits for Li-ion in BMS
Temperature Limits for Li-ion in BMS

Balancing

In applications where multiple battery cells are connected in series to achieve higher voltages, cell imbalances can occur over time due to differences in capacity, internal resistance, or aging. These imbalances can lead to reduced overall battery performance, and reduced capacity, and in extreme cases, can cause overcharging or over-discharging of certain cells, potentially leading to their premature failure. There are primarily two methods of balancing:

Active Balancing

In active balancing, the system uses additional circuitry, such as resistors, switches, or semiconductor devices, to transfer charge between cells actively. When the system detects that one cell is approaching its upper voltage limit, it diverts some of the charge from that cell to the cells with lower voltages. Similarly, during discharging, the BMS can transfer charge from cells with higher SOC to cells with lower SOC. normally in BMS HY2212 IC that is meant to balance the single Li-ion/Polymer cell is connected with a single cell. Each cell is connected to its balancer IC. The system uses a load resistor which is activated by a MOSFET. The IC has a sense circuit based on a comparator. The output signal turns the MOSFET on and off in addition to controlling the SOC of cells.

Active Balancing using HY2212 IC
Active Balancing using HY2212 IC

Passive Balancing

Passive balancing relies on the natural differences in cell internal resistance to equalize their SOC. The BMS achieves this by disconnecting the fully charged cell from the circuit, allowing it to self-discharge slightly while the other cells continue to discharge. Over time, this process brings all the cells to a similar SOC.

 

Components of a Battery Protection Circuit Board

A Battery PCB is a complex electronic system that integrates various components to perform its functions effectively. Some of the key components found in a typical Battery PCB include:

Main components of BMS
Main components of BMS

Voltage Protection IC

This integrated circuit is responsible for monitoring the battery voltage and triggering protection mechanisms when voltage thresholds are exceeded.

Current Protection IC

Similar to the voltage protection IC, the current protection IC monitors the current flow and activates safety measures when currents exceed acceptable limits.

Temperature Sensors

These sensors continuously measure the battery’s temperature, helping the BMS prevent overheating.

Balancing Circuit

In multi-cell battery packs, the balancing circuit ensures that individual cells are charged and discharged uniformly to maintain battery health.

Protection Fuses

Fuses act as safety devices that disconnect the battery in case of extreme conditions such as short circuits or overcurrent situations.

Microcontroller Unit (MCU)

The MCU serves as the brain of the Battery PCB, overseeing all the functions, processing data, and making decisions based on the inputs from various sensors and protection ICs.

Communication Interfaces

Some advanced Battery PCBs have communication interfaces like UART, I2C, or CAN, enabling them to communicate with external devices, such as battery chargers or host systems.

Connectors

The connectors facilitate the physical connection between the Battery PCB and the battery cells, as well as with the device it powers.

Types of Battery PCBs

Battery PCBs (Battery Protection Circuit Boards) come in various types, each tailored to suit different battery chemistries, applications, and requirements. Some of the common types of battery PCBs include:

Lithium-Ion (Li-ion) Battery PCB

These PCBs are specifically designed for lithium-ion batteries, which are widely used in smartphones, laptops, power tools, and electric vehicles. Li-ion battery PCBs include features like overcharge protection, over-discharge protection, and balancing to ensure the safe and efficient operation of Li-ion cells.

Lithium-Polymer (Li-Po) Battery PCB

Similar to Li-ion battery PCBs, Li-Po battery PCBs are designed for lithium-polymer batteries. Li-Po batteries are commonly used in slim and lightweight electronic devices, such as smartphones, tablets, and wearable devices.

Nickel-Metal Hydride (NiMH) Battery PCB

NiMH battery PCBs are designed for nickel-metal hydride batteries, which are commonly used in portable electronics, cordless phones, and power tools. These PCBs include protection features to ensure the safe charging and discharging of NiMH cells.

Lead-Acid Battery PCB

Lead-acid battery PCBs are designed for lead-acid batteries, commonly used in automotive starting batteries and backup power systems. These PCBs include protection features to prevent overcharging and over-discharging of lead-acid cells.

Multi-Cell Battery PCB

Multi-cell battery PCBs are designed for battery packs consisting of multiple cells connected in series or parallel to achieve higher voltages or capacities. These PCBs include balancing circuits to equalize the charge levels of individual cells, ensuring optimal performance and longevity of the battery pack.

Customized Battery PCB

In some cases, specialized applications may require custom-designed battery PCBs to meet specific requirements. Customized battery PCBs are designed based on the specific battery chemistry, voltage, capacity, and application needs.

Smart Battery PCB

Smart battery PCBs are equipped with communication interfaces, such as UART, I2C, or CAN, which allow them to communicate with external devices like battery chargers, host systems, or battery management systems. These PCBs can provide real-time data, diagnostics, and remote control capabilities, making them suitable for advanced battery management applications.

Energy Storage System (ESS) Battery PCB

ESS battery PCBs are designed for large-scale energy storage systems, such as solar energy storage systems or grid-level energy storage. These PCBs are optimized for managing high-capacity battery packs and maximizing energy efficiency.

Each type of battery PCB is designed to provide specific protection, balancing, and monitoring functions, catering to the diverse needs of different battery chemistries and applications. The choice of battery PCB depends on the specific battery technology used, the application requirements, and the level of sophistication needed in battery management.

 

Conclusion

Battery Protection Circuit Boards are fundamental components that ensure the safe and efficient operation of rechargeable batteries in a wide range of electronic devices. To encapsulate, the BMS stands as a paramount advancement in ensuring the safe, optimal, and prolonged operation of modern energy storage systems. With its intricate monitoring, balancing, and protection functionalities, the BMS plays a critical role in safeguarding batteries from overcharging, over-discharging, and other potential hazards, thereby extending their lifespan and enhancing overall system reliability. As renewable energy integration, electric vehicles, and portable electronics continue to evolve, the BMS emerges as a linchpin technology, facilitating efficient energy utilization, promoting sustainability, and contributing to the seamless integration of batteries into our daily lives. In essence, the BMS signifies an indispensable innovation driving the present and future of energy storage, enabling a more electrified and sustainable world.

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