Wearable devices such as smartwatches, wearable cameras, ECG monitors, and fitness trackers rely on custom batteries to provide power for operation. Designing wearable technologies creates significant challenges due to the size and flexibility of the devices. Wearable tech requires battery packs to be light enough for use while providing long-lasting energy.
To tackle the key power requirements for these devices, customers must develop strategies that allow for high power density without compromising on safety.
Key Requirements for Battery Packs in Wearable Devices
Space Limitations
Depending on the size of the device, battery packs have a limited amount of space. Battery packs that are to be made small will need to have high energy density. This high energy density will have the device running for long periods of time before needing to be recharged. Constantly recharging the battery in a short amount of time hampers the functionality of the device.
Small rechargeable lithium Li-ion battery for wearable device.
Power Management
Another requirement involves power management. Certain components within the wearable device may use up more power quickly, such as sensors or communication tech. Investing in components that use up less energy to operate helps to prolong the battery life and reduces the number of times that the pack requires recharging.
Safety Issues
Safety issues are additional factors in battery pack design. Wearable devices experience shocks, vibrations, impacts, and moisture penetration from rain or even sweat. They also deal with high temperatures created by the working components in the devices and from the charging/discharging phases. Finding ways to allow heat to dissipate while also ensuring that components are protected from mechanical and thermal chemical mishaps helps protect the battery from short circuits and overheating.
Balancing Energy Density vs. Battery Size
Wearable devices are designed to be worn on the wrist, over the eyes, or even attached to the arm. Due to the size, the battery packs along with the connections must be miniaturized. When making the battery pack smaller, this design feature limits the amount of energy it can hold. To overcome this issue, evaluating different battery chemistries that provide high density at smaller sizes is becoming an ideal option. Advances in lithium-based batteries, such as lithium-ion, lithium-ion polymer, and lithium-manganese-oxide, can provide higher energy densities in thinner and lightweight profiles.
Exploring newer battery chemistries such as metal-air batteries, are future advances that hold greater power possibilities for wearables. While not yet viable, this battery allows air to flow through the cell and interact with the electrodes. With advancing technology, metal-air batteries will theoretically have greater energy density than lithium-based cells.
Battery Life Optimization
With the restrictions of needing a smaller battery size, other methods must be pursued to overcome short battery life. Limiting the number of components can lower the amount of energy pulled from the battery. However, it also hampers the full functionality of the device. Instead, investing in components that have low power consumption will prolong the battery usage. Some ways to accomplish this include switching out Wi-Fi communication with Bluetooth and seeking power-saving functions.
Manufacturers are also looking into drawing energy from the user to help sustain the battery life. The movements of the user, or even the environment, may result in helping to charge the battery without needing a physical charger. Wireless charging options are also future opportunities that companies are looking into for wearable battery packs.
Safety Concerns
With all devices, safety compliance must be adhered to, especially when it comes to wearable medical devices. Equipment that relies on lithium-based batteries must abide by national and international regulations regarding the transportation and use of cells. Venting is another safety concern. A buildup of heat within the wearable device may lead to thermal runaway, swelling, and the degradation of internal components.
Impacts on wearable devices may also occur more often. This impact or shock to the battery pack may loosen connections or pierce the battery pack. Design considerations must be considered for controlling inner temperatures, venting the buildup of heat, and preventing shocks, vibrations, or impacts. Using software to monitor the health of the battery pack and to operate controls to prevent over-charging, over-discharging, and short circuits.
In other situations, wearable devices such as smartwatches and fitness bands may be exposed to water or sweat. Instituting waterproofing methods from rain and corrosion from sweat can prevent damage to the metal pins in battery packs.
Wearable Device Applications Impacting Battery Design
A challenge that cannot be overlooked is the application for the wearable device. Equipment that attaches to the arm or wrist, or fits onto the head, must bend and flex. For devices that require unique shapes and flexibility, the battery pack must also be able to bend and flex.
The battery pack needs to be designed to be rugged to withstand shocks, while also being comfortable enough to be worn for long periods. Researching and using materials that offer more flexibility without adding weight can accommodate wearable devices used in these specific applications.
Summary
The wearable device market is rapidly growing, as people become more mobile and require their devices to also be mobile. Considering design characteristics such as battery life, energy performance, safety, and flexibility allows customers to decide on the right materials and software to integrate into their devices.
Key Takeaways
- Balancing Energy Density and Size: Wearable devices require compact, lightweight battery packs with high energy density to ensure long operational life without increasing bulk. Lithium-based chemistries such as lithium-ion and lithium-polymer provide efficient power in thin, flexible profiles.
- Battery Life Optimization Strategies: Reducing power consumption by selecting energy-efficient components, switching to low-power communication methods like Bluetooth, and exploring wireless or motion-based charging can help extend battery life without increasing battery size.
- Safety Considerations in Wearable Tech: Batteries in wearable devices must withstand impacts, moisture, and high temperatures. Implementing venting, shock resistance, and software monitoring for battery health helps prevent overheating, short circuits, and degradation.
- The Role of Application-Specific Design: Wearable devices often require batteries that can bend and flex while maintaining durability. Material selection and design innovations ensure battery packs are rugged enough to handle movement while remaining comfortable for prolonged wear.
- Future Innovations in Wearable Batteries: Emerging technologies like metal-air batteries and advanced energy harvesting solutions hold the potential to revolutionize wearable battery design, offering increased energy density and self-sustaining power solutions.
