Devices are becoming smaller and lightweight. To power these applications, customers are seeking battery packs that are compact while providing efficient energy. Compact batteries are found in a variety of applications, from smartphones to medical devices. These batteries provide consistent power and a long lifespan.
When seeking compact custom battery packs, customers need to consider certain design aspects to ensure that the battery packs work with the applications for the required amount of time. Also, customers must consider the safety factors to prevent damage to both the battery packs and the devices.
What is a Compact Battery Pack?
A compact battery pack is a portable and lightweight energy storage device designed to provide power to electronic devices, tools, or appliances. It typically uses rechargeable batteries such as lithium-ion or lithium-polymer cells and is characterized by its small size and ease of portability. These battery packs come in various shapes, capacities, and configurations, making them versatile for different applications.
Prismatic battery packs are used in compact devices with limited space.
Common Design Challenges for Compact Batteries
When designing any type of battery pack, three factors come into play:
- Performance
- Structural Integrity
- Safety
These aspects can create additional challenges for compact battery packs due to their smaller design and using fewer materials to manufacture.
Performance
For performance, larger batteries provide a greater amount of energy density and storage. Due to the limited size, compact batteries cannot match the energy density or storage of larger batteries. Understanding how much power the application needs can help to determine the size of the battery.
Structural Integrity
Another design challenge is structural integrity. Factors such as vibrations, shocks, and impacts can damage the battery cell as well as create loose connections. In addition, delamination becomes a challenge depending on the format of the battery, such as pouch batteries.
Safety
Lastly, safety must focus on thermal management for the pack. Overcharging, overheating, and thermal runaway are serious and dangerous problems when using lithium-based chemistry. Controlling these factors and providing monitoring options can prevent battery damage and a loss of capacity.
Overcoming Compact Battery Design Hurdles
Increasing Battery Cell Capacity and Voltage
To get around density and capacity issues, engineers can make several design options. The first is to add additional batteries into the pack to increase voltage. If the application allows for the extra space, placing it in several batteries can increase the power available for the device. Connecting the batteries together in either a series or in parallel configuration can also impact its performance.
When compact batteries are placed in a series, you can increase voltage without increasing amp-hour capacity. If you are looking for batteries to power devices longer, the batteries can have parallel connections. Batteries placed in a parallel layout can increase capacity without increasing voltage.
Another option is to change the format of the cell. Cylindrical cells are most common, especially with nickel-based batteries. When looking for compact and thin battery sizes, prismatic and pouch batteries can accommodate devices with space limitations. Both battery formats are stackable, allowing for versatility when looking to increase capacity or voltage. However, stacking/adding more batteries into the pack can create other issues. Cells can become overly charged or overly discharged, as this creates safety concerns.
Selecting the appropriate cell chemistry or changing to different materials can also allow for better control over the capacity and voltage. Lithium has become a go-to cell chemistry when looking for batteries that provide higher amounts of power for lightweight and portable devices that have increased energy demands. Recent innovations in solid-state batteries have also shown promising trends in providing greater energy density, even more than lithium-ion, due to their solid electrolyte and lithium metallic electrode materials.
Enhancing Safety
With the smaller size of compact batteries, a major concern is safety. Stacking multiple batteries together can lead to overcharging or over-discharging of the cells. Keep in mind that not every cell may have the same amount of charge in the pack or may discharge more than the others. When charging the battery pack, damage and loss of capacity can happen to batteries with different energy levels. To combat this issue, cell balancing can ensure that each battery is discharged and recharged at the same rate.
Another issue is battery swelling. Normally, batteries are provided with space to accommodate swelling. Yet when multiple compact cells are placed together in a confined space, there is no room for swelling. In addition, humidity and heat are present when the cells are in operation, which can impact performance and cause damage. Certain pack configurations, such as pouch cells, also do not have vents built in to allow for the heat to disperse. Heat buildup can also cause delamination for pouch cells.
Designing cooling components within the device and enclosure for the battery pack may allow for cooling benefits to deal with thermal management. To prevent delamination of pouch cells, adding light stack pressure for certain cell configurations can prevent the layers from separating. Stack pressure can also improve performance for solid-state batteries to prevent dendrite formation which can cause corrosion or cracking.
Providing Structural Integrity
Impacts, vibrations, and shocks can occur during transportation, installation, or operation of the battery pack. Improving the structural integrity of compact batteries needs to be addressed. Depending on the battery format, such as prismatic, pouch, or cylindrical, can impact the number of materials along the structure of the pack. Adding more materials for protection can increase both the size and weight, leading to space issues for certain applications.
Changing the packaging design as well as using certain materials and configurations for the enclosure may further help protect the battery pack while overcoming design hurdles related to compact batteries. Consideration will need to be taken to ensure that batteries and connections are protected. This aspect can also improve the lifespan of the battery pack to prevent overheating, humidity, and temperature buildup.
Summary
Compact batteries can provide cost-effective solutions for certain applications that require small, thin, and lightweight cells. Addressing issues such as voltage, capacity, safety, and performance early in the design phase will allow you to select the right chemistry, cell configuration, and thermal management solutions while keeping costs within budget.
Key Takeaways
- Compact Battery Pack Defined: Compact battery packs are lightweight, portable power solutions designed for space-limited devices, commonly using rechargeable lithium-ion or lithium-polymer cells.
- Three Main Challenges: Designing compact batteries involves addressing performance limitations, maintaining structural integrity, and ensuring safety in small formats.
- Performance Optimization: Increasing battery cell capacity or voltage through series or parallel configurations and selecting advanced cell formats like prismatic or pouch cells can overcome energy density challenges.
- Safety Enhancements: Cell balancing prevents overcharging and over-discharging, while cooling components, thermal management strategies, and stack pressure minimize swelling, delamination, and heat-related risks.
- Structural Integrity Solutions: Designing protective enclosures and selecting appropriate materials improve durability against shocks, vibrations, and environmental factors without compromising size constraints.
- Material and Chemistry Choices: Lithium-ion remains a go-to option for compact devices, while innovations like solid-state batteries offer even greater energy density and safety improvements.
- Early Design Considerations: Addressing voltage, capacity, thermal management, and safety during the design phase ensures optimal performance while keeping costs under control.
