With the explosion of IoT devices in the last years, battery consumption is gaining its importance as a criterion in the analysis of chipsets, sensors, and IoT modules. Many of the IoT devices out in the wild must run on an extended period of time, which requires a low battery power, this is also applicable to the IoT gateways which run 24/7. In this blog, I will explain how to preserve and prevent consuming the battery life of an IoT device, and what are the steps that could be taken to help build a low battery power device.
Building a low battery power device
To ensure your IoT device is not over consuming battery is to build one that doesn’t, that means keeping the draw to an absolute minimum. The battery is calculated by dividing the battery capacity by the rate of discharge. Choosing batteries with high capacity and keeping the discharge to a minimum would result in prolonged battery life.
Choosing a battery
Choosing a battery will depend on the power consumption of your devices. The higher the devices are expected to consume battery, the higher the mAh rating should be. Some of the other factors that should be considered are:
1- Battery lifetime: Which is both the charge life and total life
2- High density: Higher density means the battery can take higher battery draws for a longer time
|Lead Acid||Rechargeable, Extremely Common, High Power Density, Durable, Wide Temperature Range||Low Energy Density, Very Heavy, Large in Size||High Current Demand Applications, Car Batteries, Large Scale Battery Banks|
|Alkaline||Extremely Common, Cheap, Decent Power Density, Low Cost||Susceptible to Natural Rupture, Generally Non-Rechargeable, Short Lifetime||Non-Rechargeable Consumer Electronics, Flashlights, Toys, Household Items|
|Nickel-Metal Hydride||High Current Ability, Less Susceptible to Memory Issues, Lower Cost||Short Storage Life, Susceptible to Overcharge||Power Tools, RC Airplanes and Drones, Portable Systems|
|Lithium Ion||Very High Energy Density, Limited Memory Effect, Long Life, Low Maintenance, Rechargeable||High Cost, Vulnerable to Stress (and Explosion!), Require a lot of Protection||Space Constrained Products, Weight Constrained Products, Cell Phones, IoT Devices, Electronic Watches|
Similar to IoT sensors, the device should draw power only when it needs to, and put the device in sleep mode in the majority of the idle time. However, planning for sleep mode would require
Consideration for power consumption upon reviving the device
Ensuring device response time is not delayed
Deciding the factors of revivals for IoT devices (Touchpad, Sense, etc.)
DRX for IoT Devices
Is a mechanism that allows the device to stop monitoring radio channels and to enter low-power consumption mode for short periods of time to reduce power usage. This power-saving technique is widely used in mobile devices today and could be used for the same reasons in IoT devices to preserve battery.
The code is written to give instructions to the device to perform a certain task(s). Every task performed will result in a spike in power consumption. Writing efficient code ensures that your applications are not performing unneeded tasks
It is no surprise that sending and transmitting data from the device will drain battery life faster than expected. To overcome this issue, certain data rules should be in place to avoid sending gigantic volumes of data.
- Aggregation: The devices should aggregate the data if it can be aggregated, for the maximum amount of time possible, to avoid sending duplicate data structures
- Unnecessary data: Avoiding sending data that is not necessary or is not being used
- Data rules: If possible, send data only when needed to (example: Motion Detection)
- Data compression: For larger data files like video, compression should be considered locally before it is transmitted
Low power sensors
Another key to minimizing power consumption is ensuring the use of low power sensors and nodes. Design of the sensor can contribute heavily to how much power is drawn from the devices. Many of the sensors will use different power saving methods (PSM) which has an energy consumption as almost being off.
Calculating the battery life of IoT devices
There are a lot of tools that assists in calculating the life on IoT devices:
Increasing power saving performance and decreasing consumption can be achieved by thinking over the design of both the software and the hardware level. The life of an IoT device is not only dependent on the battery type and capacity, but also the techniques and the design put in place when building out and IoT device and application. PSM, DRX and sleep modes are some of the most important tricks to ensure the device is not doing more work than it needs to.