Wearable devices are being intensively developed in several forms; such as watches, wristbands, eyeglasses, socks and clothing. 2015 will mark the beginning of widespread public acceptance of wearables. Besides the extremely quick evolution of wearable devices, the matter of powering wearable devices seems to move quite slowly. Even though wearable devices use the ultra-low power consumption BLE (Bluetooth Low Energy), they still need to be charged frequently. Efficient battery power for wearable devices is now the biggest challenge for producers to solve. At WT | Wearable Technologies we understand designers’ concern for implementing the ideal battery which allows for the consumer to enjoy using their device. Below is our overview with an analysis of advantages and limitations for different kinds of batteries used for wearables nowadays.
Energy harvesting is the process of taking energy from external sources and converting these energies to electrical energy. External energy sources include kinetic (locomotion, vibration, rotation), solar cell (light), thermal, piezoelectric (using excess energy derived from motion) and even radio waves. We already featured an article about energy harvesting here
Kinetic source method:
- Energy Harvesting helps wearable devices to become more independent from power outlets
- Solar energy works perfectly when placed on smart clothes, which can absorb and use energy straight from the sun.
- Solar energy provides energy even indoors.
- Thermoelectric harvesting energy is a solution for devices worn directly on skins (i.e. Smart Patches). The energy source is always available and provides high power.
- No wasted energy produced from your movement.
- Piezoelectric method generates comparably small amount of energy.
- Kinetic can produce energy throughout movement but is translated to low power
Lithium- Ion batteries
Lithium-ion batteries have finally taken the lead over nickel-cadmium batteries. They are manufacturers into the ubiquitous coin cells shape. They are sold in drugstores and used to power everything, from calculators to wearable heartrate straps. However, they provide a smaller coin cell batteries (CR1225), specific for powering wearable devices. Another popular lithium-ion battery is the pouch battery. It contains stacked batteries that are placed inside a plastic or polymer pouch cover. Pouch batteries can easily fit in almost all small packages.
- Lithium-Ion batteries are small and light
- Low maintenance because it requires no memory
- Most of them are disposable with little harm to the environment.
- Long lasting energy
- Their capacity decreases with the size of the battery
- Fragile and requires protection circuit for safe operation
- Subject to aging
- Constant changes in manufacturing
- Pouch batteries have risk of explosion because there can be gas building up between the package and the battery.
Pouch Battery manufacturing:
Thin-film batteries are super skinny. These rechargeable batteries use similar technology as lithium-ion batteries. WT wrote an article for thin-film batteries. For more details you can click here. In this section, WT would like to focus on scale advantages and disadvantages of thin-film batteries.
- Thin-film batteries are developed as a flat form, thus suitable for thin wearables (e-skin or measurement devices)
- They are super lite
- Enable high energy density for a low price
- Can be acquired in any size for different purposes
- Completely safe
- Their volume determines their energy capacity; therefore they take up much more area than a coin cell because of their thin form.
- Can require more frequent recharge because they are super tiny and skinny for a small wearable device.
Graphene batteries are built on a form of carbon, which is considerable excitement in the material-sciences world. There are now scientist working to develop this technology. Graphene batteries are expected to be the wave of the future.
- They are considered as the highest energy density of all battery types
- They also contain high storage capacity
- They are much more expensive than other batteries
- Still in development
The number of wearable devices is predicted to increase exponentially within the next 5 years. This means the demand for smaller and long-lasting batteries needs to be developed to be used inside these devices. We all perceive higher intelligence devices will drive the quest for higher energy efficiency. Depending on the use of a device, we can say there is no battery on the market considered better than another. Each battery has their own benefits and drawbacks. However, scientists and engineers are working hard on improving battery power and environmental effects. We can definitely expect for a power-up wearable industry soon!