Supercapacitors enable wearables & IoT

From smart watches to health monitoring patches, wearable devices are becoming indispensable. They need to be small, thin, long lasting and be connected. This presents a significant challenge for choosing a suitable energy source, one that a CAP-XX supercapacitor can support.

Supercapacitors deliver peak power for IoT data transmission using a coin cell …

Small coin cells such as a CR2032 are a suitable form-factor to power a wearable device. They have reasonable energy storage, ~240mAh, but poor power capability. Bluetooth Low Energy (BLE) is typically used to connect a wearable device to a cell phone app. The peak current for BLE data transmission is ~15mA. A CR2032 battery typically has an internal resistance ~10Ω when new, then this will result in a 150mV droop. As the battery is discharged, the internal resistance will increase many fold, beyond 60Ω, even with the battery still containing significant energy. This will cause the battery voltage to drop ~1V when attempting to power transmission resulting in a brown out of the BLE module. A CAP-XX supercapacitor across the battery, with an ESR of ~100mΩ reduces the voltage drop to a few mV, enabling all the energy to be extracted from the battery, increasing run time by 50%. The battery only need supply average power which is sub mW.

… and using a micro energy harvester.

An energy harvester could allow the device to run indefinitely but energy harvesters like micro generators, RF harvesters and small solar cells cannot supply the peak power required for data transmission and are an intermittent energy source. A supercapacitor can store enough energy for the wearable electronics to operate for a long period when the harvestable energy source is not available and can be charged at average current which is typically < 1mA.

For more details see Application Brief Supercapacitors Enable Wearables & IoT.