What is Active Cell Balancing in Battery Management System?

Published on: October 28, 2022
Written by Jonas Frank / Fact-checked by Nova Scarlett

Active cell balancing is a feature found in some battery management systems (BMS) that helps to keep the voltage of all the cells in a lithium-ion battery pack within safe levels. This is done by monitoring the voltage of each cell and, when necessary, transferring energy from the higher-voltage cells to the lower-voltage cells. By keeping all the cells within a certain voltage range, it helps to prevent any one cell from becoming overcharged or discharged, which can shorten the overall lifespan of the battery pack.

what is active cell balancing in battery management system

There are many different ways that active cell balancing can be implemented, but most systems use some form of MOSFETs (metal-oxide-semiconductor field-effect transistors) to control the flow of current between cells. When a cell’s voltage gets too high, the current is diverted away from that cell and into another cell with a lower voltage. This process continues until all the cells in the battery pack are within the safe voltage range.

While active cell balancing can help to prolong the life of a lithium-ion battery pack, it’s not foolproof and there are still some risks associated with using this type of system. One potential issue is that if one cell becomes damaged or degraded, it can cause problems for the rest of the cells in the pack. Additionally, if the BMS itself fails, it could lead to catastrophic failure of the entire battery pack.

Active cell balancing is a feature in battery management systems that helps to keep the cells in a lithium-ion battery pack within a safe operating range. This is done by periodically monitoring the cell voltages and currents, and then adjusting the charge and discharge rates accordingly. By doing this, active cell balancing can help to prevent premature aging of the cells and extend the overall life of the battery pack.

What are the Types of Cell Balancing?

Cell balancing is the process of equalizing the cells in a battery pack so that they all have the same voltage. There are a few different ways to do this, but the most common is to use a balance connector and an external balancing charger. The first thing that happens during cell balancing is that the charger measures the voltages of all of the cells in the pack.

It then compares these voltages to each other and determines which cells are high and which are low. The next step is to discharge any high cells until their voltage drops down to match that of the lowest cell. After all of the cell voltages are equalized, the charger will then charge up the entire pack to its full capacity.

This ensures that each cell has been given an equal opportunity to charge fully, and prevents any one cell from being overcharged or damaged. There are several benefits to cell balancing, including prolonging battery life, preventing capacity loss, and improving safety. By keeping all of the cells in a battery pack at equal voltages, you can prevent premature degradation and ensure that your batteries will last for many years to come.

What is Passive Balancing in BMS?

Passive balancing in a battery management system (BMS) is a process of automatically equalizing the voltages of cells in a lithium-ion battery pack. This is done by connecting and disconnecting the cells in a way that allows for an equal amount of current to flow through each cell, thus evening out the voltage levels. The benefit of passive balancing is that it can be done without removing the battery pack from service, and it doesn’t require any external power source – the BMS takes care of it all automatically.

This makes passive balancing an attractive option for those looking to maintain their battery packs with minimal effort. There are some drawbacks to passive balancing, however.

First, because it relies on the natural flow of current within the battery pack, it can take longer to achieve full balance than active methods (which force current through the cells).

Additionally, if one or more cells are significantly imbalanced relative to the others, passive methods may not be able to bring them into full compliance. In these cases, active methods may be necessary.

Overall, passive balancing is a simple and effective way to keep your lithium-ion battery pack healthy and balanced.

It’s important to note that while this method can work well on its own, combining it with other forms of maintenance (such as periodic cell replacement) will help ensure optimal performance and longevity from your batteries.

what is passive balancing in bms
Credit: www.electronicspecifier.com

What is Cell Balancing Technique of a Battery Pack?

In a battery pack, the cell balancing technique is used to equalize the individual cell voltages. This is done by monitoring the voltage of each cell and then charging or discharging the cells so that their voltages are equalized. This ensures that all of the cells in the battery pack are being used equally and helps to prolong the life of the battery pack.

What is the Difference between BMS And Active Balancer?

When it comes to balancing your battery pack, you have two main choices: a BMS (Battery Management System) or an active balancer. Both have their own pros and cons, so it’s important to understand the difference before making a decision. A BMS is a passive system that monitors your battery pack and ensures that each cell stays within its voltage range.

This is important because if any one cell gets too low or too high, it can cause problems for the entire pack. A BMS will also shut off your pack if it detects an imbalance, which can protect your cells from damage. The downside of a BMS is that they can’t do anything to fix an imbalance once it’s already happened.

So, if you have a cell that’s sitting at 4 volts while the rest of your pack is at 3.7, there’s nothing the BMS can do about it. In this case, you would need to manually discharge (or charge) that cell until it’s back in balance with the others. Active balancers are devices that actively monitor your battery pack and adjust the voltages of individual cells to keep them all in balance.

These are more expensive than BMS systems, but they offer some advantages as well.

First, active balancers can actually fix imbalances that have already occurredSo, if you have a cell sitting at 4 volts while the rest of your pack is at 3.7, the active balancer will automatically discharge (or charge) that cell until it’s back in balance with the others. This can save you time and effort when compared to manually balancing your cells with a BMS system.
Second, active balancers often come with built-in safety features that further protect your cells from damage due to overcharging or over-dischargingFor example, many active balancers will automatically shut off power to a cell if it starts getting too low or too high. This extra layer of protection can give you peace of mind knowing that your cells are always safe.

Smart Battery Management System With Active Cell Balancing

As we know, there are a lot of different types of batteries out there. Some are better than others and some require more maintenance than others. One type of battery that is becoming increasingly popular is the smart battery management system with active cell balancing.

This type of battery is designed to prolong the life of your battery by actively managing and balancing the cells within the battery. This helps to prevent overcharging or discharge, which can damage the cells and lead to a shorter lifespan for your battery. The smart battery management system with active cell balancing is a great option for those who want to prolong the life of their batteries and keep them working at peak efficiency.

If you are looking for a way to improve the performance of your batteries, this may be the right option for you.

Active Cell Balancing Methods

Active cell balancing is a way to keep your battery healthy and balanced. By definition, active cell balancing is the “process of equalizing the voltages of cells in a battery pack so that they are within a specified voltage range.” Most people think of this as simply making sure all the cells in their pack have an equal voltage, but there is much more to it than that!

There are two types of methods for active cell balancing: passive and active. Passive methods rely on the natural discharge characteristics of each individual cell when left idle, while active methods use external circuitry to force current through the less-charged cells until they reach equilibrium. In general, passive methods are considered simpler and more reliable, but they may not be suitable for high-power applications where quick charging is required.

Active methods, on the other hand, can be faster but may require more complex circuitry. The most common type of passive cell balancing is known as “cell monitoring” or “voltage regulation”. This method uses a microcontroller to monitor the voltages of each cell in the pack and then balances them by turning off power to the higher-voltage cells until they all reach equality.

This can be done either manually (by adjusting a potentiometer) or automatically (using software algorithms). Cell monitoring is simple and effective, but it does have some drawbacks – namely, it doesn’t work well with high-capacity batteries or those that are frequently discharged below 3V/cell. Additionally, this method cannot compensate for changes in temperature or aging effects over time.

Active cell balancing usually employs one of two techniques: charge redistribution or current injection. Charge redistribution involves using MOSFETs (metal oxide semiconductor field effect transistors) to redirect charge from higher-voltage cells to lower-voltage ones until they all reach equilibrium; this can be thought of as a “virtual wire” between cells. The current injection uses low-resistance resistors placed between pairs of unequal cells; when activated, these resistors inject current into the lower-voltage cell until its voltage rises to match that of its neighbor.

Both charge redistribution and current injection are capable of achieving very rapid balance rates (on the order of milliseconds), making them ideal for high-power applications where quick charging is required. However, both techniques also have their drawbacks – chief among them being increased complexity and cost.

Active Cell Balancing Circuit

Active Cell Balancing Circuit: Do you have a lithium-ion battery pack that needs balancing? If so, you may be able to use an active cell balancing circuit to help get the job done.

An active cell balancing circuit is a type of electronic circuit that can be used to balance the cells in a lithium-ion battery pack. This type of circuit is typically used when there are more than two cells in a battery pack, and it can be used to improve the performance and longevity of the battery pack. The way that an active cell balancing circuit works is by using transistors to connect and disconnect each cell in the battery pack from the rest of the cells in the pack.

By doing this, the voltage of each individual cell can be monitored and maintained at an equal level. This helps to prevent overcharging or discharge of any one cell, which can lead to problems with the overall performance of the battery pack. If you think that your lithium-ion battery pack could benefit from an active cell balancing circuit, then you should talk to a qualified electronics engineer about getting one designed and installed.

Active Cell Balancing Vs Passive Cell Balancing

Active Cell Balancing: In an active cell balancing system, each cell in a battery pack is monitored and balanced individually. When one cell starts to lag behind the others in terms of voltage, current, or temperature, the system kicks in and adjusts accordingly.

This ensures that all cells in the pack are always operating at peak efficiency, which maximizes both performance and lifespan.

Passive Cell Balancing: A passive cell balancing system relies on the chemistry of the battery cells themselves to maintain balance.

In this type of system, each cell is connected directly to its neighbor via a resistor. As the voltage of one cell drops, current flows from the higher-voltage cells into the lower-voltage ones through these resistors, equalizing the voltages across all cells in the process.

Active Cell Balancing IC

Active cell balancing is an important feature of modern battery management systems. By monitoring and equalizing the voltages of each individual cell in a battery pack, active cell balancing can help to extend the life of the battery and improve its overall performance. Most Li-ion batteries used in consumer electronics are made up of multiple cells connected in series.

When one cell in the pack becomes overcharged, it can cause the other cells to become undercharged, which can lead to capacity loss and reduced battery life. Active cell balancing helps to prevent this by automatically equalizing the voltages of all cells in the pack so that they remain at their optimal charge levels. There are two main types of active cell balancing ICs: linear and switch-mode.

Linear ICs use a simple voltage regulator circuit to control the flow of current between each cell in the pack. Switch-mode ICs, on the other hand, use high-speed switches to redirect currents around overcharged cells and ensure that all cells are evenly balanced. Both linear and switch-mode active cell balancing ICs offer advantages and disadvantages.

Linear ICs are simpler and cheaper to design and manufacture, but they tend to be less efficient than switch-mode ICs. Switch-mode ICs are more expensive and complex, but they offer higher efficiency levels and better overall performance.

Cell Balancing Lithium-Ion Battery

Lithium-ion batteries are one of the most popular types of batteries used in consumer electronics, but they can also be found in electric vehicles and energy storage systems. A lithium-ion battery consists of two electrodes (a positive and a negative) separated by an electrolyte. When the battery is charging, lithium ions flow from the negative electrode to the positive electrode.

When the battery is discharging, the process is reversed. Cell balancing is a process that helps to ensure that all of the cells in a battery pack are equally charged and discharged. This is important because if one cell becomes too heavily discharged, it can cause problems for the rest of the cells in the pack.

Cell balancing can be done manually or automatically. Manual cell balancing involves periodically checking the voltage of each cell in a battery pack and then equalizing them by discharge or charge as needed. Automatic cell balancing uses sensors and control circuitry to constantly monitor cell voltages and balance them as needed.

Cell balancing is an important part of maintaining a healthy lithium-ion battery pack. By ensuring that all cells are equally charged and discharged, cell balancing helps to prevent capacity loss and prolongs the life of the battery pack.

Cell Balancing Techniques

There are many ways to keep your cells healthy and balanced. Here are some cell-balancing techniques that you can use:

1. Eat a Balanced Diet

This means eating plenty of fruits, vegetables, whole grains, and lean protein. Avoid processed foods, sugary drinks, and excessive amounts of saturated and unhealthy fats.

2. Get Regular Exercise

Exercise helps to improve circulation and increase the production of endorphins, which have mood-boosting effects.

3. Practice Stress-relieving Activities Such as Yoga or Meditation

Stress can wreak havoc on your cells, so it’s important to find ways to relax and de-stress on a regular basis.

4. Get Enough Sleep

Sleep is when your body repairs itself, so be sure to get 7-8 hours per night if possible.

Active Balancer Vs BMS

When it comes to choosing between an active balancer and a BMS, there are a few key factors to consider. Both have their own unique benefits that can be advantageous in different situations. Here’s a look at the key differences between these two types of systems to help you make the best decision for your needs.

Active Balancers

An active balancer is a great choice if you need a system that can provide immediate balancing capabilities. These systems are typically used in applications where there is a high demand for quick and accurate balancing, such as in electric vehicles or aircraft.

Active balancers use sensors to constantly monitor the cells in your battery pack and adjust the discharge rate accordingly. This provides a more accurate and efficient balance than what is possible with passive systems. Additionally, active balancers often have built-in safety features that protect against overcharging or over-discharging of your cells.


A BMS, or Battery Management System, is a more comprehensive solution for managing your battery pack. In addition to providing balancing capabilities, BMSs also offer other features such as cell monitoring, voltage regulation, and temperature control.

This makes them ideal for use in large battery packs where multiple cells need to be managed simultaneously. BMSs typically require more complex wiring than active balancers, but they offer greater flexibility and functionality in return.


Active cell balancing is a feature in battery management systems that helps to prolong the life of your batteries. It does this by constantly monitoring the voltage of each individual cell in a battery pack and equalizing them when necessary. This keeps all the cells in your pack at the same voltage, which prevents any one cell from being overworked and eventually dying prematurely.

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