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Lithium-ion vs. LiFePO4 Batteries: Core Characteristics and a Practical Selection Guide

48v-lithium-golf-cart-battery

In today’s battery technology landscape, lithium-ion batteries (NMC/NCA) and lithium iron phosphate (LiFePO4 or LFP) batteries are the two dominant chemistries. Together, they power the global transition to clean energy—supporting applications ranging from electric vehicles and consumer electronics to home energy storage and telecom backup systems.

Although both belong to the lithium family, their chemical structures lead to very different performance characteristics. Understanding these differences is essential for engineers, system integrators, and buyers who want to choose the most suitable battery solution for their application.

This article provides a clear, practical comparison to help you make an informed decision.

1. Chemical Fundamentals: Where the Differences Begin

The most fundamental difference between lithium-ion and LiFePO4 batteries lies in the cathode material, which directly determines energy density, safety, lifespan, and cost.

Lithium-ion Batteries (NMC / NCA)

Lithium-ion batteries use lithium nickel manganese cobalt oxide (NMC) or lithium nickel cobalt aluminum oxide (NCA) as the cathode material.
Thanks to their high operating voltage and layered crystal structure, these batteries can store more energy in a smaller and lighter package.
22.2v 28ah lithium battery pack

LiFePO4 Batteries (LFP)

LiFePO4 batteries use lithium iron phosphate as the cathode.
Their stable olivine crystal structure provides excellent thermal stability and strong resistance to degradation, which is the foundation of their long cycle life and high safety level.

2. Five Key Performance Dimensions Compared

Below is a simplified comparison across five critical performance areas that matter most in real-world applications.

1) Energy Density

Lithium-ion: High (200–300 Wh/kg)

LiFePO4: Medium (140–180 Wh/kg)

Selection insight:
If your product requires lightweight design or long runtime—such as electric vehicles, drones, or portable electronics—lithium-ion batteries are usually the better choice.
If size and weight are less critical, LiFePO4 is often preferred for its other advantages.

2) Safety

Lithium-ion: Medium

LiFePO4: High

LiFePO4 batteries have excellent thermal stability and are much less prone to thermal runaway, even under conditions such as overcharging, short circuit, or mechanical damage.
For applications where safety is the top priority, LiFePO4 is widely regarded as an inherently safer chemistry.

3) Cycle Life

Lithium-ion: 500–1,000 cycles

LiFePO4: 2,000–5,000 cycles (or more)

Selection insight:
For applications sensitive to total lifetime cost—such as energy storage systems, commercial vehicles, or backup power—LiFePO4’s long cycle life provides a clear advantage.

4) Cost

Lithium-ion: Higher (contains cobalt and nickel)

LiFePO4: Lower (iron and phosphate are abundant)

Raw material cost and price volatility make lithium-ion batteries more expensive.
LiFePO4 batteries benefit from lower and more stable material costs, which is a key reason for their rapid adoption in large-scale commercial and energy storage projects.

5) Low-Temperature Performance

Lithium-ion: Better

About 70% capacity retention at –20°C

LiFePO4: Weaker

About 50–60% capacity retention at –20°C

Selection insight:
For cold climates or outdoor applications, lithium-ion batteries perform better.
LiFePO4 systems can still be used in cold environments, but they often require heating elements or advanced thermal management.

3. Strengths and Challenges in Detail

Advantages and Challenges of Lithium-ion Batteries

Key advantages:

High energy density enables longer driving range or smaller battery packs

Supports fast charging and high power output

Ideal for performance-focused applications

Main challenges:

More sensitive to overcharging and high temperatures

Requires a precise and reliable battery management system (BMS)

Shorter cycle life compared to LiFePO4

Higher and less stable raw material costs

Advantages and Limitations of LiFePO4 Batteries

Key advantages:

Outstanding safety and thermal stability

Very long cycle life, reducing cost per kWh over time

No cobalt or nickel, making it more environmentally friendly

Stable performance over many years of use

Main limitations:

Lower energy density

Larger and heavier packs for the same capacity

Reduced performance in low-temperature environments

4. Application Scenarios: Which Battery Should You Choose?

Choose Lithium-ion If Your Priority Is:

Maximum energy density

Long-range electric vehicles

Drones and aviation-related systems

High-end consumer electronics

High power output

Power tools

Performance hybrid or electric vehicles

Cold climate operation

Outdoor or automotive applications in low temperatures

Choose LiFePO4 If Your Priority Is:

Safety and long-term reliability

Energy storage systems (ESS)

Solar storage

Telecom base station backup power

Lower total cost of ownership

Commercial EVs

Electric buses and logistics vehicles

Shared mobility fleets

Fixed installations with high safety requirements

Home energy storage

Security and monitoring equipment

Marine and UPS backup systems
lithium-ion-battery-charger

5. Future Trends: Competition or Coexistence?

The market is not moving toward a “winner-takes-all” solution. Instead, it is evolving toward application-based optimization.

Technology Evolution

Lithium-ion batteries are shifting toward high-nickel, low-cobalt formulations to increase energy density while reducing cost.

LiFeO4 batteries are improving pack-level efficiency through innovations such as CTP (Cell-to-Pack) and blade battery designs, which significantly increase volumetric energy density.

Mixed Battery Strategies

Some automakers now adopt dual chemistry strategies:

Entry-level models use LiFePO4 for cost and safety

Premium models use lithium-ion for performance and range

System-Level Optimization

Regardless of chemistry, system design is critical.
Battery performance and safety heavily depend on:

Battery management system (BMS)

Thermal management design

Manufacturing quality and consistency

In many cases, a well-designed LiFePO4 system can outperform a poorly designed lithium-ion system—and vice versa.

Conclusion: There Is No Perfect Battery, Only the Right One

The choice between lithium-ion and LiFePO4 batteries is ultimately a strategic trade-off between energy density and safety/longevity.

If every gram and every kilometer matters, lithium-ion is often the right answer.

If long term stability, safety, and life cycle cost are more important, LiFePO4 is the smarter choice.

There is no universal “best battery”—only the most suitable solution for a specific application.

When selecting a battery, always return to the core question:
Do you need maximum performance today, or stable and reliable operation for the next ten years?
The answer will guide you to the right technology.

 

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18650 vs. 26650: Two Classic Cylindrical Lithium Batteries — How to Choose the Right One

3.7V-18650-battery-cell

In the world of cylindrical lithium-ion batteries, 18650 and 26650 are two of the most well-known and widely used formats. They have been on the market for many years and are still essential in many industries today.

The numbers in their names act like an “ID card”:

The first two digits indicate the diameter (in millimeters)

The next two digits indicate the length (in millimeters)

The final “0” means the battery is cylindrical

For example:

18650 = 18 mm diameter, 65 mm length

26650 = 26 mm diameter, 65 mm length

Although they share the same length, the 8 mm difference in diameter leads to clear differences in capacity, performance, cost, and application. Understanding these differences is a key step in designing efficient and reliable battery-powered products.
26650 lifepo4 battery and Li Ion Customized Battery Manufacturing

1. Key Differences: More Than Just Size

The table below highlights the main differences between 18650 and 26650 lithium-ion batteries.

Physical Size

18650:

Diameter: 18 mm

Length: 65 mm

26650:

Diameter: 26 mm

Length: 65 mm

Both batteries have the same height, but the larger diameter of the 26650 gives it more internal volume and higher weight, which directly affects capacity.

Typical Capacity

18650:

Common range: 1,800 mAh – 3,500 mAh

26650:

Common range: 4,500 mAh – 5,000 mAh

Under the same battery chemistry, a 26650 cell usually offers more than 50% higher capacity than an 18650 cell, simply because it is larger.

Energy Density

18650: Higher energy density

26650: Lower energy density (compared to 18650)

The 18650 format has been produced on a massive scale for many years. Its manufacturing process is extremely mature and highly standardized, which allows it to achieve better energy density per unit volume.

Discharge Performance

18650:

Very wide range

From standard cells (around 3C) to high-power cells (10C or higher)

26650:

Usually moderate discharge rates

Most models focus on 1C–3C continuous discharge

The 18650 market offers more high-rate power cells, making it suitable for applications that require strong current output.
The 26650 focuses more on a balance between capacity and stable continuous discharge.

Cost and Market Availability

18650:

Lower cost

Extremely widely available

Many brands and suppliers

26650:

Higher cost per cell

Fewer manufacturers and options

The 18650 is an industry-standard cell. Large-scale production creates strong cost advantages.
In comparison, the 26650 supply chain is smaller, which affects both price and availability.

Typical Applications

18650 batteries are commonly used in:

Laptops

Power tools

High-end flashlights

Drones

Electric bicycles and scooters

26650 batteries are commonly used in:

Solar street lights

Energy storage systems

UPS systems

Telecom backup power

Large lighting equipment

In simple terms:

18650 = flexibility and performance

26650 = capacity and durability

2. Shared Advantages: Why They Remain Popular

Despite their differences, both 18650 and 26650 batteries share the core advantages of high-quality cylindrical lithium-ion cells:

High energy density compared with NiMH or lead-acid batteries

Long cycle life, often more than 500 cycles to 80% capacity

No memory effect, allowing flexible charging

Stable nominal voltage (typically 3.6V–3.7V)

Easy pack assembly, as cylindrical cells are easy to connect in series and parallel using holders or brackets

These advantages make them reliable building blocks for battery packs of many sizes and voltage levels.

3. Inherent Limitations: What System Design Must Address

Both formats also share some limitations that designers must consider:

Fixed shape
Cylindrical cells cannot fully use irregular internal space, unlike pouch batteries

Protection required
A protection circuit or battery management system (BMS) is essential to prevent overcharge, over-discharge, over current and short circuits.

Safety design challenges
In extreme thermal runaway cases, cylindrical metal shells may vent gas. Proper pack-level thermal design and safety spacing are important.

These issues do not prevent their use, but they must be addressed through good system-level design.

4. How to Choose: A Practical Decision Guide

Choosing between 18650 and 26650 is mainly about matching the battery to your core requirements.

Step 1: Space and Energy Requirements

If your product has limited space and needs high energy density, 18650 is usually the better choice.

If space allows a larger diameter and you want higher capacity per cell to reduce the number of parallel cells, 26650 is a strong option.

Step 2: Discharge Needs and Cost

For applications that require high current or high power, such as power tools or fast-moving drones, high-rate 18650 cells are recommended.

For applications that focus on medium-rate continuous discharge and long runtime, such as energy storage or lighting, 26650 cells often provide better value.

For cost-sensitive, high-volume projects, the mature 18650 supply chain usually offers more competitive pricing.

Application-Based Summary

Choose 18650 when designing:

Portable consumer electronics

Lightweight electric mobility products

Power tools or devices with high power demand

Choose 26650 when designing:

Energy storage systems

Long-runtime lighting solutions

Products with enough space and strict capacity requirements per cell
high-quality-18650-battery-holder-materials

Conclusion

18650 and 26650 batteries are not competitors, but complementary solutions.

The 18650 dominates portable and high-performance applications thanks to its excellent standardization, energy density, and cost advantages.

The 26650 holds a strong position in energy storage and long-runtime applications due to its higher single-cell capacity and durability.

When making a decision, move beyond the simple question of “which is better.”
Return to the basics of product design:

What are your space limits, energy needs, discharge requirements, and cost targets?

Once these questions are answered, the right battery format will become clear.

 

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The Role of ICs and MOSFETs on a Lithium Battery Protection Board

If you open a lithium battery protection board and take a closer look, two components immediately stand out: the protection IC and one or more MOSFETs.

 

They are always there, whether it is a simple single-cell protection board or a high-current battery pack used in industrial equipment.

 

People often ask which one is more important, or what exactly each of them does.

 

In reality, they serve very different purposes, and confusing their roles is one of the most common misunderstandings in lithium battery design.

 

A protection board only works properly when the IC and the MOSFETs work together, each doing what it is designed to do.

 

What the Protection IC Actually Does

 

At its core, the protection IC is not a power component. It does not drive motors, supply loads, or carry large currents. Its job is much simpler — and at the same time, much more critical.

 

The protection IC is responsible for monitoring and decision-making.

 

In most lithium battery protection designs, the IC continuously monitors:

 

  • Cell voltage or pack voltage
  • Charging overvoltage
  • Discharging undervoltage
  • Charge and discharge current (through a sense resistor)
  • Short-circuit conditions

 

In some designs, temperature via an external NTC

 

These values are compared against fixed thresholds that are built into the IC. Once any parameter goes beyond its allowed range, the IC decides that the battery is no longer operating safely.

 

That decision happens very quickly, often within microseconds or milliseconds.

 

What is important to understand is that the IC does not stop the current by itself.

It only outputs a control signal.

 

Why the IC Is Often Called the “Brain”

 

Calling the protection IC the “brain” of the protection board is not just a metaphor — it is a practical description of how the system behaves.

 

The IC determines:

 

  • When charging should stop
  • When discharging should stop
  • Whether an overcurrent event is temporary or a real fault
  • How fast the protection should react

If the IC’s thresholds are poorly chosen, the battery may:

 

Trigger protection too early and appear unreliable. Or worse, fail to protect the cells at all

 

In real projects, many field issues traced back to batteries are not caused by the cells themselves, but by incorrect IC selection or incorrect parameter matching.

 

What MOSFETs Do on a Protection Board

 

While the IC makes decisions, the MOSFETs are the components that physically control the current path.

 

A MOSFET on a protection board works as an electronic switch. When it is turned on, current flows normally between the battery and the external circuit. When it is turned off, that current path is interrupted.

 

When the protection IC detects an abnormal condition, it sends a signal to the MOSFET gate. The MOSFET then switches off and isolates the battery from the charger or the load.

 

This is the moment where protection actually happens.

 

Without MOSFETs, the IC would have no way to enforce its decisions.

 

Why There Are Usually Two MOSFETs

 

One detail that often raises questions is why protection boards typically use two MOSFETs connected back-to-back, rather than a single one.

 

The reason is simple but important.

 

A single MOSFET contains a body diode, which allows current to flow in one direction even when the MOSFET is turned off. This means a single MOSFET cannot fully block current in both charge and discharge directions.

 

By using two MOSFETs in a back-to-back configuration, the protection board can:

 

  • Block charging current
  • Block discharging current
  • Prevent leakage through the body diode

 

This arrangement allows the IC to independently control charging and discharging behavior, which is essential for proper lithium battery protection.

 

MOSFETs and Current Handling in Real Designs

 

From a system perspective, MOSFETs are usually the most stressed components on a protection board.

 

They must handle:

 

  • Continuous operating current
  • Peak current during acceleration or motor startup
  • Short-circuit current before protection kicks in

 

Key MOSFET parameters such as Rds(on), current rating, and thermal performance directly affect:

 

  • Heat generation
  • Efficiency
  • Long-term reliability

 

In high-current battery packs, MOSFET selection and PCB layout matter just as much as the IC itself.

It is not uncommon to see perfectly good protection logic paired with undersized MOSFETs, leading to overheating or premature failure.

 

In practice, many “protection board failures” are actually MOSFET thermal failures, not IC failures.

bms architecture

How the IC and MOSFETs Work Together

 

To understand the interaction between the IC and MOSFETs, it helps to look at a simple real-world scenario.

 

Imagine a battery pack being discharged until the voltage drops too low.

 

The cell voltage gradually decreases during discharge

 

The protection IC continuously monitors this voltage

 

Once the undervoltage threshold is reached, the IC determines that further discharge would damage the cell

 

The IC sends a control signal to the MOSFET gate

 

The MOSFETs turn off

 

The battery is disconnected from the load

 

The entire sequence happens automatically and very quickly.

The IC decides when protection is needed, and the MOSFETs determine whether the current can actually be stopped.

 

A Common Misconception

 

One of the most common misunderstandings is assuming that MOSFETs “provide” the protection by themselves.

 

In reality:

 

The IC defines the protection logic

 

The MOSFETs provide the switching capability

 

If the IC logic is wrong, even the best MOSFETs cannot protect the battery properly.

If the MOSFETs are poorly selected, even a well-designed IC cannot safely interrupt high current.

 

Battery safety is never the result of a single component. It is the result of how these components work together.

custom lithium battery

What This Means for Battery Pack Design

 

From a practical engineering point of view:

 

The protection IC determines accuracy, reliability, and functional behavior

 

The MOSFETs determine current capability, heat generation, and durability

 

In low-current applications, this distinction may not seem critical.

In high-current or long-life systems, it becomes one of the most important design considerations.

 

Understanding this relationship helps explain why two battery packs with similar cells can behave very differently in the field.

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A Practical Comparison of Lithium-ion, LiFePO₄, NiMH, and Lead-acid Batteries

b2b-battery-solutions

When people talk about batteries, the conversation often starts with numbers — energy density, cycle life, cost per watt-hour. In practice, however, battery selection is rarely that simple.

Different battery chemistries behave very differently once they are placed into real products, operating in real environments, with real users. What looks good on a datasheet does not always translate into long-term reliability or the lowest total cost of ownership.

In this article, we compare four commonly used rechargeable battery technologies — Lithium-ion (NCM/NCA), Lithium Iron Phosphate (LiFePO₄), Nickel-Metal Hydride (NiMH), and Lead-acid — from a practical, application-driven perspective.

 

1. Overall Performance Comparison

 

Item Lithium-ion (NCM/NCA) LiFePO₄ (LFP) NiMH Lead-acid
Energy Density High Medium Low Very low
Size / Weight Smallest & lightest Larger than NCM Large Largest & heaviest
Cycle Life 800–1500 cycles 2000–6000 cycles 500–1000 cycles 300–500 cycles
Safety Medium (BMS-dependent) High High Medium
Discharge Rate High (3C–10C) Medium–High (1C–5C) Medium Low
Cost per Wh Medium–High Medium Relatively high Lowest
Maintenance Low Low Low High
Environmental Impact Good Very good Average Poor (lead content)

2. Understanding the Differences Beyond Specifications

At a high level, all rechargeable batteries work on the same principle: energy is stored and released through reversible chemical reactions. The difference lies in the materials used and how stable those reactions are under stress — heat, high current, deep discharge, or long-term cycling.

From an engineering standpoint, the most important questions are usually:

How long will the battery last in this application?

How tolerant is it to misuse or abnormal conditions?

How much protection and system-level control does it require?

What will it really cost over several years of operation?

With that in mind, let’s look at each chemistry in more detail.

 

Lithium-ion Batteries (NCM / NCA)

 

Lithium-ion batteries using NCM or NCA cathodes are widely known for one reason: they pack a lot of energy into a small space. This is why they dominate consumer electronics, drones, and many mobile robotic systems.

 

In typical designs, these cells operate at around 3.6–3.7 V nominal voltage, with energy densities reaching 180–260 Wh/kg, far higher than most other rechargeable batteries.

 

Where Lithium-ion Performs Well

 

If your product has strict size or weight limits, lithium-ion is often the first and sometimes the only realistic option. High discharge capability also makes it suitable for applications that demand short bursts of high power.

 

With a properly designed BMS, lithium-ion batteries can charge quickly, deliver stable performance, and achieve good overall efficiency.

 

Practical Limitations

 

The trade-off is safety and complexity. NCM/NCA cells are less forgiving than other chemistries. Overcharging, overheating, or cell imbalance can quickly become a serious issue if protection is inadequate.

 

From experience, lithium-ion systems rely heavily on:

 

Accurate voltage and temperature monitoring

Cell balancing

Well-defined operating limits

 

This adds cost and design effort. In addition, cycle life is usually shorter than LiFePO₄, especially in high-load or high-temperature environments.

 

Typical Use Cases

 

Consumer electronics

Drones and UAVs

Compact robotic platforms

High-performance portable equipment

custom-lithium-ion-batteries

Lithium Iron Phosphate Batteries (LiFePO4)

 

LiFePO₄ batteries have earned their reputation mainly because of stability and safety, not because they win on headline energy density numbers.

 

With a nominal voltage of around 3.2 V per cell and energy density typically in the 120–160 Wh/kg range, they are physically larger than NCM-based lithium-ion batteries for the same capacity.

 

Why Many Engineers Prefer LiFePO₄

 

What LiFePO₄ offers in return is predictability. The chemistry is extremely stable, even under abusive conditions. Thermal runaway is far less likely, and the battery tends to fail gracefully rather than catastrophically.

 

Cycle life is another major advantage. In many real-world applications, 2000–6000 cycles is achievable, which makes LiFePO₄ particularly attractive for systems expected to run for many years.

 

Voltage output is also very stable during discharge, which simplifies system design in industrial and energy storage applications.

 

Known Trade-offs

 

The main downside is size and weight. If space is limited, LiFePO₄ may not be suitable. Low-temperature performance is also weaker compared to some other chemistries, and cold environments may require additional thermal considerations.

 

Typical Use Cases

 

Energy storage systems

Electric vehicles focused on safety and longevity

Industrial equipment

AGVs and forklifts

Telecom backup power

48v golf cart battery upgrade

Nickel-Metal Hydride Batteries (NiMH)

NiMH batteries sit somewhere between lithium-based batteries and lead-acid in terms of performance. They are not cutting-edge, but they are proven and reliable.

 

Operating at around 1.2 V per cell, NiMH batteries have relatively low energy density, typically 60–120 Wh/kg, which limits their use in modern compact designs.

 

Strengths in Real Applications

NiMH batteries are known for being robust and safe. They tolerate overcharging better than lithium-ion and perform reasonably well across a wide temperature range.

 

In applications where simplicity matters and advanced battery management is not desirable, NiMH can still be a practical choice.

 

Practical Drawbacks

Higher self-discharge means NiMH batteries are not ideal for long standby periods. In addition, their cost per watt-hour is often higher than lithium-based alternatives, which reduces their appeal in new designs.

 

Typical Use Cases

 

Medical devices

Measurement and instrumentation equipment

Older hybrid vehicles

Retrofit or replacement battery packs

Lead-acid Batteries

 

Lead-acid batteries are the most mature rechargeable battery technology still in use today. Despite their age, they remain common in applications where cost and simplicity outweigh performance considerations.

 

With energy density typically below 50 Wh/kg, lead-acid batteries are heavy and bulky, but they are also inexpensive and easy to manage.

 

Why Lead-acid Is Still Used

 

The technology is well understood, charging methods are simple, and the supply chain is fully established worldwide. For backup systems that are rarely cycled, lead-acid batteries can still make economic sense.

 

Limitations That Matter

 

Deep discharge significantly shortens lifespan, and cycle life is generally limited to 300–500 cycles. Environmental concerns related to lead handling and disposal are also becoming more restrictive in many regions.

 

Typical Use Cases

 

UPS systems

Engine starting batteries

Emergency power supplies

Cost-sensitive backup systems

 

Choosing the Right Battery in Practice

 

In real projects, battery selection is rarely about finding the “best” chemistry. It is about finding the most appropriate one.

 

When size and weight are critical, lithium-ion (NCM/NCA) is often the only viable option.

When safety, longevity, and predictable behavior matter most, LiFePO4 is usually preferred.

When simplicity and robustness are required, NiMH can still be a reasonable solution.

When upfront cost is the primary concern, lead-acid remains relevant.

 

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The Battery BMS Design with Dual Circuits

bms architecture

A dual-circuit BMS (Battery Management System) refers to a battery management system that utilizes two separate, independent circuits to manage and protect a battery pack. These circuits are typically designed to handle battery monitoring, protection, charging, and discharging etc., with dual circuit enhance the overall performance, safety, and reliability of the system.

 

Key Characteristics of a Dual-Circuit BMS:

 

1.Redundancy:

A dual-circuit BMS provides redundancy, meaning that if one circuit fails, the other can take over, ensuring that the battery system continues to function properly. This is especially important for critical applications where failure is not an option (e.g., electric vehicles, drones, or medical equipment).

 

By having two circuits that are identical in function, the overall reliability of the system is increased. The backup circuit ensures continuous operation even in the event of a failure in the primary circuit. For example, if one circuit fails due to a hardware issue, the other circuit can still manage the battery, preventing catastrophic failures.

 

2.Increased Safety and Fault Tolerance:

With two independent circuits, the system is less vulnerable to failure since the malfunction of one circuit doesn’t necessarily lead to a complete system failure. This is crucial in high-reliability applications, where a backup system is needed to maintain operation in case of an issue.

 

3.Improved System Stability:

By having two circuits dedicated to specific tasks, the overall system becomes more stable because each circuit can be optimized for its function without interfering with the other. This leads to more accurate battery monitoring, better protection mechanisms, and more efficient energy management.

 

4.Improved Reliability:

By having two circuits that are identical in function, the overall reliability of the system is increased. The backup circuit ensures continuous operation even in the event of a failure in the primary circuit. For example, if one circuit fails due to a hardware issue, the other circuit can still manage the battery, preventing catastrophic failures.

 

5.Failover Protection:

This design is essentially a failover strategy. The system constantly monitors the status of each circuit, and if one circuit experiences issues (such as a malfunctioning component), the other circuit automatically takes over its duties. This is critical in environments where system uptime is essential.

 

 

 

6.Simplicity:

While a dual-circuit BMS with the same functions is more straightforward than a system with split tasks, it still requires careful design to ensure that both circuits are synchronized properly and do not conflict with one another. The complexity here lies in managing the two circuits so they can seamlessly switch roles in case of failure.

li-ion-battery-bms

Disadvantages of Dual-Circuit BMS Design:

 

1.Increased Cost:

A dual-circuit design requires additional hardware components, which raises the material and design costs. Moreover, the complexity of designing and manufacturing two circuits makes the overall system more expensive.

 

2.Larger Space Requirements:

Due to the additional circuit, dual-circuit BMS systems generally require more space, which could be a challenge for applications with limited space, such as small drones or electric tools.

 

3.Power Consumption:

Running two circuits simultaneously can lead to additional power consumption. This is particularly important for applications that require long standby times, such as electric vehicles’ battery management systems, where increased power consumption may reduce system efficiency.

 

4.Maintenance and Debugging Complexity:

Troubleshooting and maintaining a dual-circuit BMS is more complex than a single-circuit system. Handling the coordination between the two circuits and diagnosing issues when they arise can be more challenging.

 

A dual-circuit BMS design is suitable for applications that demand high levels of safety, reliability, and fault tolerance, such as large battery packs or critical mission devices. While it increases costs and space requirements, its advantages typically outweigh the disadvantages in high-performance or safety-critical environments. The decision should be based on the specific application and a careful balance of these factors.

Protection-functions-of-the-BMS

Applications of Dual-Circuit BMS:

 

Dual-circuit BMS designs are commonly used in applications where:

 

—For the high reliability is crucial (e.g., electric vehicles, aerospace, medical devices).

—For safety is a top priority, and the system cannot afford to fail (e.g., critical backup systems, military applications).

—For large battery systems require robust protection and management, such as large-scale energy storage or industrial equipment.

 

In essence, a dual-circuit BMS ensures that the battery is monitored and controlled with increased precision and security, making it suitable for demanding and mission-critical applications.

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Why LiPo Batteries Need Extra Space and Why Swelling Is Dangerous

Lipo Battery

Lithium Polymer (LiPo) batteries are widely used because they are light and powerful. However, many people ask: Why can’t a LiPo battery be made exactly the same size as the battery case? The answer is safety.

 

Why LiPo Batteries Cannot Fit Tightly in the Case

 

LiPo batteries need extra space to “breathe.” During long-term use, a LiPo battery may slightly expand. If the battery is put into a very tight case with no space, it may be pressed by the case, which is very dangerous.

 

There are four main reasons:

 

Space for normal expansion

During charging and discharging, a small amount of gas is slowly produced inside the battery. This can cause the battery thickness to increase by about 1–3% over time. Extra space allows this normal aging expansion safely.

 

Avoid internal damage

If the battery is squeezed, stress points may form inside. This can damage the separator or electrodes and cause an internal short circuit, which may lead to fire or thermal runaway.

 

Better heat dissipation

A tight case blocks heat from escaping. Heat buildup will speed up battery aging and gas generation, making the situation worse.

 

Protection from shock and vibration

In case of drops or vibration, the reserved space (usually with soft foam) helps absorb impact and protect the battery.

 

For safety, engineers usually keep 0.5 mm to 2 mm space on each side, depending on battery size and capacity.
lipo-battery-puffing

 

Why LiPo Batteries Slightly Expand During Use

 

Slight expansion is a normal aging process and happens slowly. It mainly comes from two chemical reasons:

 

SEI layer changes

A protective layer (called SEI) forms on the anode. During every charge and discharge, it slightly breaks and repairs itself, producing a very small amount of gas.

 

Slow electrolyte decomposition

Over a long time, the electrolyte may slowly react and create gas.

 

This kind of expansion is even and slow and usually appears after many charge cycles. It is not immediately dangerous.

 

What Is Dangerous Swelling (Battery Bulging)?

 

Dangerous swelling, also called bulging, is not normal and is very unsafe.

Item Normal Expansion Dangerous Bulging
Speed Very slow (months or years) Fast (few cycles)
Shape Even and flat Uneven, pillow-like
Feeling Slightly soft Very hard and tight
Cause Normal aging Overcharge, overheating, damage

Can a Swollen LiPo Battery Still Be Used?

 

No. Never use a bulged LiPo battery.

 

Here is why:

 

Internal damage

Bulging means the internal structure may already be damaged, increasing the risk of short circuits.

 

Chemical instability

Fast gas generation shows the battery chemistry is out of control.

 

High fire risk

Any further charging, discharging, or even resting may cause fire or explosion.

 

Never try to fix it

Do not puncture the battery. This can cause immediate fire because air reacts with the battery materials.

LiPO-Battery

Conclusion

 

LiPo batteries will slightly expand during normal use, so safe design must include extra space. Tight battery cases are dangerous. If a battery shows bulging or hard swelling, it must be stopped and recycled immediately.

 

Good design and correct handling are the key to LiPo battery safety. If you have any LiPO battery requirements, please don’t hesitate to contact us. We’re pleased to quote our best price for your evaluation.

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The Power of Simplicity: Why We Use Only 4 Large Cells for 12.8V 20Ah LIFePO4 Batteries

solar-lifepo4-battery

Today, battery technology is developing very fast. Many LiFePO4 battery packs are becoming more and more complex. However, we want to ask an important question:

Does real safety come from complex systems, or from simple and smart design?

Our answer is simple design.

We recently launched a new 12.8V 20Ah LiFePO4 battery pack. Inside, it uses only four large 40135 cells (3.2V 20Ah each) connected in series. This is not a compromise. It is a careful and responsible design choice.

We believe: fewer cells mean higher safety, longer life, and better reliability.

Part 1: Safety Comes from “Less Is More”

The Hidden Risk of Parallel Cells

Many traditional battery packs use many small cells. To get enough capacity, they first connect cells in parallel, then connect groups in series.

This design has hidden risks:

Cell inconsistency
No two cells are exactly the same. Over time, small differences cause internal current between parallel cells. This wastes energy and makes aging faster.

Thermal runaway risk
If one cell overheats, nearby parallel cells may heat up together. The failure can spread very fast, like falling dominoes.

BMS blind spots
The BMS usually checks only the whole group voltage, not each single cell. Early problems are hard to find.

Our Solution: Large Cells, Series Only

We do not use parallel cells.

Our battery uses four large 20Ah cells connected only in series. This brings clear benefits:

No internal current
In a series circuit, all cells carry the same current. There is no internal circulation problem.

Better fault isolation
Each cell is independent. If one cell has an issue, the risk does not spread quickly.

More accurate BMS monitoring
The BMS checks each cell’s voltage and temperature, so small problems can be found early.

In short, we turn a complex system into a clear and safe team, where every cell is visible and controlled.
48v-lithium-batterie

Part 2: More Benefits of Large Cells

1. Better Use of Space

Many small cells need extra space for holders, connectors, and cooling paths. These parts do not store energy.

Large 40135 cells have a high space efficiency. The battery structure is simpler, so more space is used for energy.

Result:

More energy in the same case

Or a smaller and lighter battery for the same energy

2. Better Consistency, Longer Life

A battery pack is limited by its weakest cell.

Large cells have more stable production quality. Also, it is much easier to match 4 cells than 16 or more small cells.

With good consistency, no parallel stress, and precise BMS balancing, all cells age at the same speed.
This helps the battery reach over 3000 charge cycles and a long calendar life.

3. Higher Reliability, Lower Cost Over Time

Fewer cells = fewer failure points
Less welding, fewer connections, higher reliability.

Simpler BMS work
No complex parallel balancing, better system stability.

Lower total cost
Even if the initial cost is higher, the long life and low maintenance reduce the total cost over time.

Part 3: Wide Range of Applications

Thanks to its safety, long life, and stability, this 12.8V 20Ah LiFePO4 battery is a perfect replacement for lead-acid batteries.

1. Outdoor and Home Energy

Portable power stations

RV and marine auxiliary power

Home backup power and solar storage

2. Light Electric Vehicles

E-bikes and e-scooters

Electric wheelchairs and mobility scooters

Golf carts and low-speed vehicles

3. Garden and Cleaning Tools

Electric lawn mowers

Cleaning robots and floor machines

4. Commercial and Industrial Use

AGV and mobile robots

Testing instruments and security systems

Emergency lighting and communication backup.

boat-battery-size

Conclusion: Simple Design for a Safer Future

Making systems more complex is easy. Making them simpler and safer needs real engineering thinking.

By using only four large cells, we focus on what truly matters:
safety, reliability, and long-term performance.

A good battery should work quietly and safely in the background—not become a risk.

If you are looking for a safe, long-life, and reliable energy solution, we are happy to discuss with you.

 

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Fire Resistance of Lithium Batteries

48v-lithium-batterie

The fire resistance and flame retardancy design of lithium battery is an important aspect of ensuring battery safety during use and storage. The electrolyte and other chemicals inside lithium batteries are prone to ignition, especially under conditions such as overcharging, short-circuiting, or impact.

 

Causes of Fire or Explosion:

 

Overcharging: When a battery is overcharged, the temperature inside the battery increases rapidly, potentially triggering electrolyte decomposition, which releases flammable gases.

 

Short Circuit: In the case of a short circuit, the excessive internal current leads to localized overheating, which could cause the electrolyte to decompose or catch fire.

 

Mechanical Damage: If the battery casing is damaged, causing internal structural failure, electrolyte leakage or thermal runaway could result in a fire.

 

High Temperature Environments: Prolonged exposure to high temperatures accelerates electrolyte decomposition, increasing the risk of combustion.

 

To prevent fires and battery explosions, many lithium battery manufacturers and researchers have adopted the following fire-resistant and flame-resistance measures:

 

1. Improvement of Electrolyte Flame Resistance

Some high-performance lithium batteries use flame-resistance electrolytes or replace liquid electrolytes with solid-state electrolytes. One of the main advantages of solid-state batteries is their low flammability, effectively reducing the risk of fire.

 

Here are some common types of flammable electrolytes, which mainly refer to electrolyte components that could trigger fires or explosions under uncontrolled conditions:

 

Organic Solvent-based Electrolytes:

-Dimethyl Carbonate (DMC)

-Ethylene Carbonate (EC)

-Diethyl Carbonate (DEC)

-Propylene Carbonate (PC)

Lithium Fluoride Salts in Electrolytes

Phosphate-based Electrolytes

Chlorine-containing Solvents in Electrolytes

Unstable Electrolyte Formulations

 

Types of Solid-state Electrolytes

There are several types of solid-state electrolytes, including:

 

Ceramic-based Electrolytes:

Lithium Lanthanum Zirconate (LLZO)

Lithium Phosphorus Oxynitride (LiPON)

Garnet-type Electrolytes

 

Polymer-based Electrolytes:

Polyethylene Oxide (PEO)

Polyvinylidene Fluoride (PVDF)

 

Sulfide-based Electrolytes:

Li2S-P2S5 (Lithium Sulfide-Phosphorus Sulfide)

 

2. Battery Case and Protective Materials

 

Flame-resistance Casings: Many lithium batteries use flame-resistance casing materials (such as plastics and aluminum alloys) to enhance the fire resistance of the battery. These casings help to suppress flame spread in case of overheating or short circuits.

 

For example, following are the plastics materials that has fire resistance:

  1. Polycarbonate (PC)
  2. Polypropylene (PP)
  3. Polyvinyl Chloride (PVC)
  4. Flame-resistanceNylon (PA)
  5. Polyester (PET)
  6. Epoxy Resin (EP)
  7. Polytetrafluoroethylene (PTFE)
  8. Flame-resistanceABS(Acrylonitrile Butadiene Styrene)
  9. Polystyrene (PS)
  10. Polyetheretherketone (PEEK)

 

Fire-resistant Insulation Materials: Some batteries also use insulation materials inside the battery to prevent the fire from spreading when the battery is exposed to heat.

LiFeo4 12V 150AL Battery

3. Thermal Management System

 

Thermal Management BMS (Battery Management System): Some batteries’ BMS are equipped with thermal management systems that monitor battery temperature in real-time and disconnect the battery in case of overheating to prevent thermal runaway.

Heat Dissipation Design: By designing the battery pack with proper arrangements and ventilation, the risk of battery overheating is reduced.

For example, heat sinks or enhanced ventilation systems are added to ensure heat dissipation.

 

4. Use of Flame-resistance Additives

 

Flame resistances (such as phosphate-based compounds or nitrogen-containing compounds) are added to the electrolyte or solid-state electrolyte to improve fire resistance. These flame resistances form a protective layer inside the battery, isolating oxygen and reducing the chance of fire.

 

5. Thermal Protection Devices

 

PTC (Positive Temperature Coefficient) Thermal Protectors: These thermal protectors automatically increase resistance when the battery temperature becomes too high, limiting current flow and preventing overheating or short-circuit-induced fires.

 

Fuses: In the event of overcurrent, fuses automatically disconnect the circuit, cutting off the current to prevent fire.

 

NTC (Negative Temperature Coefficient) Thermistors : Widely used as thermal protection devices in electronic systems, including batteries, to prevent overheating and ensure the safe operation of devices. NTC thermistors are key components in many Battery Management Systems (BMS) and other thermal protection applications due to their unique characteristics.

6. Thermal Runaway Design

 

Thermal runaway refers to the rapid increase in temperature caused by internal or external factors (such as overcharging or short circuits), which ultimately leads to a fire. To prevent thermal runaway, some lithium batteries are designed with multiple protective measures, such as internal isolation and built-in heat dissipation channels, ensuring rapid heat dissipation in the event of thermal runaway, preventing the spread of fire.

 

These fire-resistant and flame-resistance designs effectively improve the safety of lithium batteries during use. However, even with these fire protection measures, proper usage and maintenance are still key to ensuring battery safety. For example, do not expose batteries to high temperatures, avoid overcharging or deep discharging, and prevent mechanical shock to the battery.

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Why Your Bluetooth Battery Level Appears Incorrect (and How to Fix It)

bms soc drift

Does this sound familiar? Your Bluetooth app shows 50% battery remaining—yet the device suddenly powers down.

At Himax Electronics, we know exactly how frustrating this feels. You’re using your device with confidence, trusting the battery reading, and then—without warning—it slows down or shuts off. It can be alarming, and it certainly disrupts your day. But the good news is: in most cases, the battery itself is perfectly fine. What’s actually happening is something we call SOC drift—a natural “memory deviation” inside the BMS over time.

Below, we explain why this happens and how a simple weekly full-charge routine can restore accuracy.

bluetooth battery soc

Why Does SOC Become Inaccurate?

SOC (State of Charge) is recorded and calculated by your battery’s BMS. A helpful way to think about it is like a high-end mechanical watch. Over time, tiny environmental influences—like magnetic fields—can slowly affect its accuracy. It’s still a great watch, but it needs to be reset occasionally. Your battery’s SOC estimation works the same way.

bms soc drift

Inside LiFePO4 and NMC battery packs, the BMS constantly manages many parameters. SOC is only one of them, but it’s especially sensitive to long-term variations. The BMS uses voltage, current, temperature, Coulomb counting (ampere-hour integration), and sometimes Kalman filtering to estimate SOC. Under ideal conditions, this is accurate within about ±3%.

However, real-world conditions aren’t ideal. Daily use brings voltage swings, temperature changes, partial charges, and variable loads. These tiny variations build up over days or weeks, causing the displayed SOC to drift from the true value. That’s why your app can still show 40–60% even when the battery is actually close to empty.

 

The Simple Fix: Calibrate at Full Charge (Continuous charging until 100%).

Fortunately, recalibrating SOC is easy—you just need one full, uninterrupted charge cycle. Here’s the recommended method:

1.Fully discharge the battery.

2.Disconnect all loads and chargers so the pack is out of active use.

3.Let the battery rest for 2–4 hours to stabilize at its true open-circuit voltage (OCV).

4.Recharge using the correct LiFePO4/NMC CC–CV charger.

5.Charge straight to 100% in one continuous session.

6.After reaching 100%, continue charging for 1–2 additional hours to establish a precise full-charge baseline.

 

This process resets both the “empty” and “full” energy markers inside the BMS, clearing accumulated drift.

lifepo4 battery calibration

How Often Should You Calibrate?

Our engineering team’s testing shows that, with current BMS technology, SOC accuracy remains stable for about one week after calibration. Because Bluetooth-enabled batteries display SOC directly to users, weekly full charging is currently the most reliable way to maintain accurate readings.

→ We recommend performing one full, uninterrupted charge every week.

It’s simple, practical, and ensures you always know exactly how much power you have.

 

Why Accurate SOC Matters

Accurate SOC isn’t just a number on a screen—it directly affects your safety, your battery life, and your experience.

1. Protect Your Battery

Preventing deep discharge keeps the cells healthy and preserves long-term capacity.

2. Save Money and Avoid Damage

LiFePO4 batteries can last over a decade when used correctly. But frequent over-discharge accelerates aging, increases internal resistance, and in severe cases can cause swelling or internal short risks.

3. Avoid “Battery Anxiety”

Few things feel worse than expecting plenty of battery, only to be stranded with none. Whether you’re out on the water with a full catch or running critical equipment, accurate SOC prevents unpleasant surprises.

 

Looking Forward

Himax electronics truly understand how inconvenient SOC drift can be, and we’re not ignoring it. Our engineering team is actively developing more advanced SOC algorithms to reduce drift in future BMS designs.

Your feedback drives our improvements—thank you for your patience and trust. If you ever have questions, or if your battery still seems inaccurate after calibration, please reach out to us at sales@himaxelectronics.com or leave a message. We’re here to help, always.

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How to Use a Parallel Battery Charger — Complete, Safe Guide for Home, Construction & RC Users

battery-charger

Parallel battery charging is a convenient way to increase your total battery capacity and extend runtime without boosting voltage. For users in homes, workshops, or construction sites — especially those working with LiPo packs or 12V systems — knowing how to safely use a parallel battery charger can prevent damage, swelling, or even fire risks. This guide walks you through the setup, safety checks, and real-world best practices backed by expert data and trusted authorities.

 

What Is a Parallel Battery Charger?

battery-charger

A parallel battery charger is designed to charge multiple batteries that are connected in parallel — meaning all positive terminals are joined together, and all negative terminals are joined together.

In this setup:

 

Voltage remains the same,

Capacity (Ah) adds up, increasing total runtime.

 

Parallel vs Series — Quick Comparison

 

Series connection: increases voltage (e.g., two 12V → 24V).

Parallel connection: increases capacity (two 12V 100Ah → still 12V, but 200Ah).

Use parallel charging when you need longer runtime at the same voltage, such as powering solar systems, tools, or drones.

 

 

When Should You Use Parallel Charging?

1. Home Backup or Solar Energy Systems

 

In off-grid solar setups, parallel charging keeps voltage stable while extending storage capacity — perfect for powering appliances longer.

 

2. Construction Sites and Power Tools

 

Builders and technicians often parallel-charge tool batteries to keep devices running continuously without downtime.

 

3. RC & Drone Enthusiasts

 

For LiPo packs, parallel charging saves time by charging multiple packs at once, provided they’re matched properly.

 

Always ensure batteries have the same voltage and similar capacity before parallel charging to avoid imbalance or internal short-circuiting.

 

Before You Start — Safety Checks & Preparation

battery testing

Battery Matching Matters

 

Only connect batteries that share the same voltage, chemistry, and age. Mixing old and new batteries or Li-ion and LiFePO4 cells can cause dangerous voltage imbalances.

 

Inspect for Damage or Swelling

 

If you see puffing or swelling — especially with LiPo batteries — do not charge them. Swollen batteries indicate gas buildup or internal breakdown. According to Battery University

, charging a swollen LiPo can lead to fire or explosion. Dispose of damaged cells immediately through certified e-waste centers.

 

Work Area Preparation

 

Charge in a well-ventilated, fire-resistant area. Avoid flammable materials nearby and use a LiPo safety bag for additional protection.

 

Equipment & Tools You Need

 

  • A parallel-capable charger (multi-bank or smart LiPo charger).

 

  • Balance leads or parallel boards for equal voltage distribution.

 

  • Fuses or circuit breakers to prevent current surge.

 

  • Correct cable gauge to handle the total current safely.

 

  • LiPo safety bag or metal charging container.

 

Step-by-Step: How to Use a Parallel Battery Charger

Step 0 — Preparation

 

Wear insulated gloves and ensure your workspace is dry, non-conductive, and ventilated.

 

Step 1 — Match Batteries

 

All batteries must be the same voltage and state of charge (SoC). Measure with a voltmeter — the difference should not exceed 0.05V per cell for LiPo packs.

 

Step 2 — Connect Batteries in Parallel

 

Connect positive to positive, negative to negative using cables of equal length to balance resistance. Secure connections tightly.

 

Step 3 — Add Balancing Wires or Fuses

Fuse-connection

Use balance leads to equalize cell voltage between packs. Insert a fuse on each positive terminal to isolate a faulty battery if something goes wrong.

 

Step 4 — Connect the Charger

 

Attach the charger’s positive and negative leads to the parallel bank, not to each battery separately.

 

Using multiple chargers on the same parallel bank can cause current backflow and overheating — avoid this practice.

 

Step 5 — Set the Charger Parameters

 

Select correct chemistry: Li-ion, LiPo, AGM, or lead-acid.

 

Set voltage limit: typically 4.2V per cell for LiPo (follow manufacturer specs).

 

Set charge rate: around 1C or lower for longevity (e.g., 2A for a 2000mAh pack).

 

Step 6 — Monitor During Charging

 

Watch for abnormal heat, swelling, or odors. If temperature rises rapidly or a pack inflates, stop immediately and disconnect safely.

 

Step 7 — Finish & Store

 

When fully charged, disconnect the charger first, then the batteries. Store LiPo batteries at storage voltage (3.7–3.8V per cell) if not used for a while.

 

Special Notes for Swollen LiPo Users

battery Recycl

Why LiPo Batteries Swell

 

Swelling is caused by gas buildup from overcharging, overheating, or internal damage. It’s an irreversible process indicating cell failure.

 

Never Charge or Compress a Swollen LiPo

 

Attempting to recharge or flatten a swollen battery can rupture the pouch and ignite flammable electrolytes. The U.S. Consumer Product Safety Commission (CPSC)

advises users to immediately stop use and dispose of such batteries properly.

 

Safe Disposal

 

Place the battery in a non-metallic container, cover terminals with tape, and take it to a local hazardous waste collection site. The National Fire Protection Association (NFPA) also provides detailed consumer safety guidelines for lithium-based products.

 

Common Mistakes & Troubleshooting

 

❌ Mixing batteries of different voltages or capacities.

 

❌ Charging each battery with a separate charger while connected in parallel.

 

❌ Ignoring balance leads — leading to uneven charging.

 

⚡ If charger shows error or overheat:

 

Disconnect all batteries.

 

Check fuse, wiring, and voltage.

 

Replace any pack with >0.05V deviation.

 

Best Practices Checklist

 

✅ Check all batteries for equal voltage and chemistry.

✅ Use fuses and equal-length cables.

✅ Avoid charging swollen or damaged cells.

✅ Charge in a fireproof area.

✅ Monitor constantly — never leave charging unattended.

 

Recommended Chargers & Accessories

 

When choosing a charger:

 

Look for parallel-capable smart chargers with auto-balance and overcurrent protection.

 

Ensure it supports your battery chemistry (LiPo, LiFePO4, AGM).

 

Choose trusted brands with UL or CE certifications and safety records.

 

FAQ

 

1. Can I charge two 12V batteries in parallel with two chargers?

Usually not. Using two chargers can cause uneven current flow and potential shorting. Use one properly rated charger for the entire parallel bank.

 

2. My LiPo battery is slightly swollen. Can I still charge it?

No. Even slight swelling means internal damage. Follow safe disposal steps from the CPSC lithium battery safety guide

 

3. How can I balance batteries when charging in parallel?

Use a parallel balance board or balance wires on your charger to equalize cell voltages. Always verify voltage uniformity before charging.