Custom Battery Pack Thermal Management: When Is It Needed?

Not every custom battery pack requires an active cooling system.

However, thermal management should be considered whenever a lithium-ion battery operates under conditions that can generate significant heat, such as high current, high C-rate, long duty cycles, high ambient temperatures, or demanding charging conditions.

For OEM and ODM projects, thermal performance is not determined by battery capacity alone. Cell selection, current requirements, operating conditions, BMS protection, mechanical design, and the application’s duty cycle all influence how a custom battery pack behaves during operation.

This guide explains when thermal management should be considered, how BMS temperature monitoring contributes to battery safety, and what OEMs should evaluate when developing a custom lithium battery pack.

What Is Battery Thermal Management?

Battery thermal management refers to the methods used to monitor and control the temperature of a battery during charging, discharging, and operation.

For lithium-ion batteries, temperature can affect:

• Battery performance
• Charging and discharging behavior
• Cycle life
• Safety
• Overall system reliability

Heat is generated during battery operation. One important source of heat is the electrical resistance inside the cells and battery pack.

A simplified relationship is:

P = I²R

Where:

• P = heat generated
• I= current
• R = electrical resistance

As current increases, resistive heat generation can increase significantly.

This is why a battery pack designed for a high-power industrial application may have very different thermal requirements from a battery used in a low-power IoT device.

What Factors Affect the Thermal Performance of a Custom Battery Pack?

There is no single capacity or current value that determines whether a battery pack needs thermal management.

OEM engineers should evaluate several factors together.

Discharge Current and C-Rate

The amount of current a battery delivers has a direct impact on heat generation.

C-rate describes the charge or discharge current relative to the battery’s capacity.

For example, a battery operating at a relatively low C-rate may experience different thermal conditions from a battery of the same capacity operating at a much higher C-rate.

Therefore, when developing a custom battery pack, engineers need to consider both:

• Battery capacity
• Required operating current

Capacity alone does not define the thermal requirements.

Continuous and Peak Current

Peak current and continuous current should be evaluated separately.

A battery may experience a short-duration peak load when a motor starts, accelerates, or encounters increased resistance.

In contrast, continuous high-current operation can result in sustained heat generation.

For OEM battery development, it is useful to define:

• Continuous discharge current
• Peak discharge current
• Peak duration
• Load frequency
• Duty cycle

These parameters provide a clearer picture of the actual operating conditions.

Duty Cycle

A battery used for a few minutes may have different thermal behavior from one operating continuously for several hours.

Repeated charge and discharge cycles can also contribute to heat accumulation.

For this reason, battery testing should reflect the actual operating pattern of the final product whenever possible.

Ambient Temperature

The surrounding environment also matters.

A battery operating in a controlled indoor environment may have different thermal requirements from one installed in industrial equipment exposed to elevated ambient temperatures.

OEMs should define the expected operating temperature range during the battery design stage.

Charging Conditions

Thermal evaluation should include charging as well as discharging.

Charging current, charging speed, and charging conditions can influence battery temperature.

If a product requires relatively fast charging, the charging profile should therefore be included in the battery requirements provided to the battery manufacturer.

Battery Pack Design and Enclosure

The physical design of the battery pack also affects thermal behavior.

Factors can include:

1. Cell arrangement
2. Internal component layout
3. Available space
4. Enclosure design
5. Heat dissipation paths
6. Sealed or enclosed structures

A battery pack installed inside a compact product enclosure may have fewer opportunities for heat dissipation than a battery operating in a more open environment.

Does Every Lithium Battery Need Active Cooling?

No.

Thermal management does not necessarily mean installing a fan, liquid cooling system, or another active cooling solution.

For many custom battery packs, thermal requirements can first be addressed through appropriate battery engineering.

This can include:

• Selecting suitable cells
• Selecting an appropriate battery configuration
• Optimizing pack layout
• Considering the operating current
• Monitoring battery temperature
• Implementing BMS protection
• Testing the battery under representative operating conditions

The goal is not to add the most complicated cooling system possible.

The goal is to develop a battery pack that can operate reliably under its intended conditions.

For this reason, thermal management should be treated as part of battery pack design, rather than as a separate feature added after the battery has been developed.

When Does a Custom Battery Pack Need More Thermal Evaluation?

Some operating conditions require closer thermal consideration.

This does not mean that every application in the higher-risk categories automatically requires active cooling.

Instead, these conditions indicate that thermal performance should receive more attention during battery development and validation.

Thermal Management for Different Applications

Industrial Equipment

Industrial equipment can place demanding requirements on a custom battery pack.

Depending on the application, batteries may experience:

• High continuous current
• Repeated peak loads
• Long operating periods
• Variable ambient temperatures
• Compact installation spaces

For these applications, thermal requirements should be considered together with electrical, mechanical, and BMS requirements.

The battery should be designed around the actual operating profile of the equipment.

Medical Devices

Medical devices can require a combination of:

• Reliable power
• Compact battery dimensions
• Stable operating performance
• Appropriate protection functions
• Long operating periods

A battery installed inside a medical device may have limited space and limited heat dissipation.

Therefore, battery thermal behavior should be considered alongside the product’s enclosure, operating current, charging requirements, and mechanical constraints.

For medical battery projects, thermal considerations are part of the broader battery reliability and safety design process.

IoT Devices

Many IoT devices have relatively low power requirements.

However, some IoT products operate continuously, use compact enclosures, or are installed in outdoor environments where temperature conditions can vary significantly.

For these applications, thermal management may focus less on active cooling and more on:

• Appropriate cell selection
• Battery configuration
• Temperature monitoring
• BMS protection
• Compact pack design
• Operating temperature requirements

The thermal requirements should therefore be evaluated according to the actual IoT application rather than assuming that all IoT batteries have low thermal demands.

How Does a BMS Help With Battery Temperature?

The Battery Management System (BMS) is an important part of battery protection.

A BMS can monitor battery operating conditions and provide protection when predefined limits are exceeded.

For temperature protection, temperature sensors can monitor battery temperature.

If a high-temperature condition is detected, the BMS can trigger high-temperature protection according to the battery’s configured protection parameters.

A simplified protection process can be represented as:

Temperature Sensor → Temperature Monitoring → High Temperature Detected → High-Temperature Protection

This provides an additional layer of protection during abnormal operating conditions.

However, BMS protection should not be considered a replacement for proper battery design.

The BMS can respond to a temperature condition, but the battery pack should still be designed according to the application’s electrical, mechanical, and environmental requirements.

How Should OEMs Approach Thermal Management During Battery Development?

Thermal considerations should be introduced early in the development process.

A typical custom battery development process can include:

Define Application Requirements

Start with the actual product requirements:

• Voltage
• Capacity
• Continuous current
• Peak current
• Charging current
• Operating time
• Duty cycle
• Operating temperature
• Available installation space

Select Appropriate Cells

Cell selection should consider more than capacity and energy density.

Depending on the application, engineers may also evaluate:

• Power requirements
• Discharge capability
• Internal resistance
• Cycle life
• Operating conditions

The selected cell should match the actual requirements of the product.

Develop the Battery Pack

The battery configuration and physical layout should be developed around the product’s available space and electrical requirements.

Mechanical constraints can also affect how heat behaves inside the battery enclosure.

Integrate BMS Protection

The BMS can be configured according to the battery’s electrical and protection requirements.

Temperature monitoring and high-temperature protection can provide an additional safety layer.

Build and Test a Prototype

Prototype testing allows engineers to evaluate the battery under representative operating conditions.

Temperature behavior should be evaluated together with electrical performance and other project requirements.

Validate Before Mass Production

Before moving into mass production, the battery design should be validated against the requirements of the final application.

This helps identify potential issues before large-scale manufacturing.

How to Test the Thermal Performance of a Custom Battery Pack

Thermal testing should reflect how the battery will actually be used.

Depending on the application, testing may consider:

• Continuous discharge
• Peak discharge
• Charging
• Operating temperature
• Duty cycle
• Product enclosure
• Expected operating duration

Temperature sensors can be used to monitor battery temperature during testing.

For a custom battery project, test conditions should be defined according to the customer’s application rather than relying only on generic laboratory conditions.

This is particularly important for industrial and medical applications where the battery may operate continuously or under demanding load conditions.

Thermal Management Is More Than Cooling

When people hear “battery thermal management,” they often think about cooling systems.

But thermal management starts much earlier than cooling.

The more important question is not : How can we cool this battery?

It is: How should the battery be designed to operate within the required conditions?

That requires consideration of the complete battery system:

Application Requirements
↓
Cell Selection
↓
Electrical Design
↓
BMS Design
↓
Mechanical Design
↓
Temperature Monitoring
↓
Prototype Testing
↓
Validation
↓
Mass Production

The appropriate approach depends on the application.

A low-power IoT device may require relatively simple thermal considerations, while an industrial battery operating under high loads may require significantly more detailed evaluation.

Custom Battery Pack Development for Industrial, Medical and IoT Applications

Hypercell provides custom battery OEM/ODM services for applications including industrial equipment, medical devices, and IoT products.

Custom battery development can involve:

• Cell selection
• Custom voltage and capacity
• Battery pack configuration
• BMS engineering
• Temperature monitoring and protection
• Mechanical design
• Prototype development
• Testing and validation
• Certification support
• Mass production

Our approach is to develop the battery around the requirements of the end product rather than simply selecting an off-the-shelf battery.

For applications with specific current, operating temperature, space, charging, or duty-cycle requirements, these factors can be evaluated during the battery development process.

Frequently Asked Questions

Q: Does every lithium-ion battery need thermal management?

No. Thermal requirements depend on factors such as current, C-rate, duty cycle, ambient temperature, charging conditions, cell characteristics, and battery pack design.

Q: When does a battery pack need active cooling?

Active cooling may be considered when the battery operates under demanding thermal conditions that cannot be adequately managed through appropriate cell selection, pack design, heat dissipation, and other design approaches.

Q: Does a higher-capacity battery generate more heat?

Not necessarily. Heat generation depends on factors including current, internal resistance, operating conditions, and duty cycle—not battery capacity alone.

Q: Can a BMS prevent a battery from overheating?

A BMS can monitor battery temperature and trigger protection when predefined temperature limits are reached. However, BMS protection does not replace appropriate battery pack design and thermal evaluation.

Q: How does C-rate affect battery temperature?

A higher C-rate generally means higher current relative to battery capacity, which can increase heat generation. Actual temperature rise also depends on cell characteristics, internal resistance, operating time, and other design factors.

Q: What information should I provide when requesting a custom battery pack?

OEM customers should provide voltage, capacity, continuous current, peak current, charging requirements, operating temperature, duty cycle, available space, and application requirements. More detailed application information allows engineers to better evaluate the battery design.

Conclusion

Not every custom lithium battery pack needs active cooling.

However, thermal management should be considered whenever the application involves high current, high C-rate, long duty cycles, high ambient temperatures, demanding charging conditions, or limited heat dissipation.

For OEMs, the best approach is to consider thermal requirements from the beginning of battery development.

A custom battery pack is more than Cells + BMS + Enclosure.

Its electrical design, cell selection, BMS protection, mechanical structure, temperature monitoring, testing, and validation all need to work together around the requirements of the final product.

Need a custom battery pack for an industrial, medical, or IoT application? Contact Hypercell to discuss your battery requirements.