Why You Need an Active Balancing BMS?

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Why You Need an Active Balancing BMS?

High-voltage rechargeable battery systems are becoming critical in various applications, including electric vehicles and grid load balancing. These battery packs feature a series/parallel array design of lithium polymer or LiFePO4 cells, specifically chosen for their superior energy density and peak power capabilities. However, series-connected battery stacks pose a challenge: battery balancing. Imbalanced discharge profiles caused by natural performance variations can curtail system runtime and lead to significant energy wastage. To address this challenge, battery balance plays an important role in ensuring optimal battery performance and life. As a BMS manufacturer, Mokoenergy writes this blog to show you the transformative impact of active balancing BMS on battery management across various industries. Let’s explore the world of active balancing BMS to understand its significance and how it revolutionizes battery management.

Passive Balancing BMS vs. Active Balancing BMS

Battery balancing can be accomplished using two main methods: passive balancing and active balancing. Passive balancing relies on resistors to discharge excess charge from high-voltage cells, while BMS active balancing uses sophisticated components like transformers, inductors, or capacitors to transfer energy between cells. Passive balancing is cost-effective and suitable for battery packs with lower capacity, but it dissipates energy as heat, reducing overall system efficiency. On the other hand, active balancing provides higher efficiency, ensures optimal charge distribution, and offers superior performance for larger battery packs.

Passive Balancing BMS vs. Active Balancing BMS

The Role of Active Balancing BMS

The Active Balancing BMS contributes a lot to ensuring optimal battery performance. It is designed to redistribute charge among battery cells during both discharge and charging cycles. By actively transferring charge from stronger cells to weaker cells, BMS active balancer ensures that all cells are fully utilized, thus maximizing runtime and reducing the frequency of charge-discharge cycles. As a result, it extends battery life, increases charging efficiency, and reduces the likelihood of overcharging or deep discharges.

During discharge, BMS with active balancer ensures that the battery stack is fully depleted, thereby preventing weaker cells from limiting the system’s runtime. Conversely, during the charging process, it allows the battery stack to achieve its maximum capacity, ensuring effective utilization of all the available energy.

Benefits of BMS with active balancing

The implementation of active balancing BMS yields numerous benefits, including:

Extended Battery Life: Active balancing enhances cell consistency, ultimately extending the overall battery pack’s lifespan.

Improved System Reliability: By preventing individual cells from prolonged overcharging or discharging, active balancing enhances the safety and reliability of the entire battery system.

Enhanced Energy Efficiency: Active balancing optimizes the charge utilization of each cell, leading to increased energy efficiency and reduced waste.

Cost Savings: With prolonged battery life and reduced maintenance costs, active balancing results in significant cost savings over the battery system’s lifetime.

Sustainable Battery Management: Active balancing promotes the efficient use and sustainability of battery systems, aligning with the growing global focus on eco-friendly technologies.

Types of active battery balancing methods: Energy Transfer vs. Parallel Equalization

Selecting the right active balance method is a critical aspect when designing an efficient and dependable Battery Management System (BMS). Several factors need to be considered to determine the most suitable active balancing approach for a specific battery pack. Now, let’s dig into the various types of active balancing BMS and their design considerations:

Energy Transfer

Active cell balancing BMS using energy transfer involves transferring energy between cells through intermediate devices like transformers, inductors, or supercapacitors. Unlike passive balancing, active balancing minimizes energy losses and maximizes efficiency.

  1. Inductive Balancing

Inductive balancing utilizes inductors to transfer energy between cells. When the voltage of a particular cell becomes significantly higher than others, the inductor shunts the excess energy, leveling the cell voltages. Subsequently, during the charging process, the stored energy in the inductor is released to balance low-voltage cells. Inductive balancing offers higher efficiency than passive methods and is well-suited for medium-sized battery packs.

  1. Capacitive Balancing

Capacitive balancing involves using capacitors to store and transfer energy between batteries. Similar to inductive balancing, when a cell’s voltage exceeds the others, the capacitor absorbs the excess energy. During charging, the capacitor releases energy to balance low-voltage cells. While capacitive balancing is efficient, it requires careful control to prevent overcharging and discharging the cells.

  1. Transformer-Based Balancing

Transformer-based balancing uses flyback transformers to transfer energy between cells. The transformer serves as both an energy source and a sink, converting energy between magnetic and electric forms. Transformer-based balancing provides high efficiency and is suitable for large battery packs with high power requirements.

Parallel Equalization

Parallel equalization involves dividing the charging current during the charging process, directing more charge to cells with lower voltage. This approach does not involve energy transfer components like inductors or capacitors and does not “rob the rich to give to the poor,” minimizing additional charge and discharge burdens.

However, parallel equalization is most effective during the static charging process and may not be suitable for dynamic charging scenarios. It is commonly used for smaller battery packs where the complexity and cost of energy transfer methods are not justified.

Active Balance MethodDescriptionSuitabilityEfficiencyApplication
Inductive BalancingUses inductors to transfer energy between cells.Well-suited for medium-sized battery packs.Higher efficiency compared to passive balancing.Medium-sized battery packs.
Capacitive BalancingInvolves capacitors to store and transfer energy between cells.Suitable for medium-sized battery packs.Efficient but requires careful control to prevent overcharging and discharging.Medium-sized battery packs.
Transformer-Based BalancingUses flyback transformers for energy transfer between cells.Suitable for large battery packs with high power requirements.High efficiency.Large battery packs.
Parallel EqualizationDivides charging current to balance cells with lower voltage.Effective during static charging but not suitable for dynamic charging.No energy transfer components are needed.Smaller battery packs.

What should you consider before choosing your Active Balancing methods?

When it comes to application-specific active battery management systems, there are several key factors to take into account for a well-optimized solution.

  1. Battery Pack Size

The size of the battery pack is a crucial consideration. For smaller battery packs with lower power requirements, passive balancing proves advantageous due to its simplicity and cost-effectiveness. This method efficiently handles balancing needs without adding unnecessary complexity. On the other hand, larger battery packs with higher power demands can benefit from active balancing methods such as inductive or transformer-based balancing.

  1. Power Requirements

It is essential to carefully consider the power demands of the specific application. Battery packs with higher power needs necessitate more efficient balancing methods, making transformer-based or inductive balancing more suitable.

  • Energy-Consuming Equilibrium (Passive Balancing) for Battery Packs Within 10AH

For battery packs with a capacity of up to 10AH, the energy-consuming equilibrium, also known as passive balancing, proves to be a more suitable option. This method effectively utilizes resistors to equalize cell voltages and is particularly well-suited for lower-capacity battery packs. It offers a straightforward and cost-effective solution to maintain balance in smaller systems.

  • Inductive Balancing with Flyback Transformers for Battery Packs in the Tens of AH Range

Battery packs with capacities in the tens of AH range require more efficient balancing methods. Inductive balancing, which utilizes flyback transformers in conjunction with battery sampling, becomes a feasible option. The flyback transformer serves as an energy transfer device, efficiently balancing the cell voltages. This approach offers higher efficiency compared to passive balancing, making it ideal for medium-sized battery packs.

  • Independent Charging Module for Battery Packs in the Hundreds of AH Range

For battery packs with capacities in the hundreds of AH range, an independent charging module is the preferred option. In such large-scale battery packs, the balanced current required for efficient balancing is around 10 A. If the number of series sections within the battery pack is substantial, the balanced power can become significant. To handle this higher power demand safely, it is advisable to employ an external DC-DC or AC-DC balance through an independent charging module. This ensures effective balancing while minimizing any potential risks associated with the high power involved.

  1. Application Specifics

Different applications might have unique operational requirements. For example, in electric vehicles, fast charging and discharging rates might necessitate efficient active balancing methods to optimize performance and ensure safety.

By considering these factors, one can determine the most suitable active balancing approach for a given battery pack size, power requirements, and specific application needs.

Mokoenergy’s Active Balancing BMS Solutions

Discover MOKOEnergy‘s comprehensive range of BMS with active cell balancing, specially crafted to cater to a diverse array of application requirements. As a leading BMS solutions provider, Mokoenergy ensures top-notch products that perfectly align with various industry needs. Whether it’s energy-consuming equilibria for smaller battery packs or advanced inductive and transformer-based balancing for larger systems, Mokoenergy ensures optimal battery performance and longevity.

High-Efficiency Bidirectional Balancing BMS

Mokoenergy’s Active Battery Balancer stands as an exemplary high-efficiency, bidirectional active balance control IC, essential for achieving active balancing in BMS systems. This advanced IC can simultaneously balance up to 6 Li-Ion or LiFePO4 cells connected in series.

The Active Battery Balancer features a non-isolated, synchronous flyback power stage, ensuring high-efficiency charging and discharging. Integrated control circuits diligently monitor individual cell voltages, triggering energy transfer processes when voltage imbalances are detected. This sophisticated active balancing battery management system efficiently manages charge redistribution among cells, optimizing battery performance.


Designing an efficient and reliable active balancing BMS is essential for optimizing battery performance and extending battery life. By carefully considering factors like battery pack size, power requirements, and application specifics, engineers can choose the most suitable active cell balancing method. Mokoenergy’s expertise in designing and manufacturing active balancing BMS solutions ensures that customers receive reliable, high-efficiency, and cost-effective battery management systems for their specific applications. With active balancing technology at the forefront, Mokoenergy continues to pave the way for a sustainable and eco-friendly future in the battery management industry. Contact us if you’re looking for any Battery balancing solutions!


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