In our personal lives, many of us typically give little thought to the selection of batteries in home devices. A television remote — assuming that we haven't switched to a smartphone-controlled smart TV — requires little more than a primary AA or AAA battery. However, as domestic devices become smarter and responsible for increasingly complex or important tasks, the performance of the underlying battery becomes more crucial for design engineers to consider. Here, Robert Brown, marketing executive at battery manufacturer Accutronics, explains the evolving requirements of batteries for smart home technology.

According to Fortune Business Insights, the home automation market will be valued at approximately USD 114 billion by 2025, growing at a compound annual growth rate (CAGR) of 12.1 per cent from 2017's USD 45.8 billion market size. Some of the reasons behind this continued growth could be the increased reliance on technology in the developed world (research shows ‘people generally spend an average of three hours and 15 minutes on their phones every day') and the added user convenience it brings.

However, this is only one part of the reason for smart home growth. The wider adoption of the Internet of Things (IoT) into our homes is also driven by the potential for increased accessibility, making life easier for people with physical impairments or mobility issues, and smarter domestic security devices.

From an electronic design perspective, the growth of smart home devices has been influenced by — and in turn, also accelerated — the shrinking footprint of devices and sensors.

One example is the humble smoke alarm. Ultralife Corporation, Accutronics' parent company, has been manufacturing long-lasting 9V batteries for smoke alarms for almost 30 years. In recent years, we've seen these devices begin to transition to smaller 3V batteries, such as CR123A cells that were originally used exclusively in cameras. These same cells are also growing in popularity for powering other smart home technologies, such as smart light sensors.

The rise of the CR123A
CR123A batteries are an ideal choice for battery-powered smart sensors, because they boast a lightweight and compact footprint alongside high voltage capacities. Yet as with all batteries, not all CR123A batteries are the same. Design engineers should specify CR123A batteries with very specific characteristics to make the most of their product. Besides high energy capacity, which provides extended operating time for sensors, engineers should look for batteries with minimal self-discharge and a gentle voltage curve over their lifespan.

The steady voltage curve is particularly important because it directly impacts overall sensor performance. The voltage curve indicates how the current draw of the battery changes over time, with a gentle curve meaning that the battery's performance is consistent until the energy is depleted.

This is a common characteristic in CR123A batteries with a lithium chemistry, such as Ultralife's lithium manganese dioxide battery for smart sensors. These batteries have an improved internal spiral construction that provides a higher capacity than is available from similar products on the market, while remaining long lasting for home automation functions.

Securing smart homes
Although CR123A batteries are integral to many of the latest smart home technologies, they may not be the best option for all applications. For example, security systems such as smartphone-synced cameras and smart locks are among the most popular smart home technologies. In some cases, these systems can be wired into the electrical network for a constant supply of power with batteries as a backup.

However, many smart locks are often retrofitted onto existing doors, which makes wiring impractical. As such, batteries must be used and must also be able to provide reliable, long-lasting performance, as an unexpected fault in the battery could result in someone being locked out of their home. But something like a smart lock requires a specific type of battery that can occupy a thin, small footprint while still providing a stable discharge curve to ensure consistent discharge, high energy density for longer lasting performance and a wide operating temperature to account for weather conditions.

The optimum choice to meet these unique set of requirements is a battery that uses Thin Cell technology, which was specifically developed to meet the demanding requirements of connected devices. Thin Cell batteries balance high power density and capacity with a slim profile — as thin as 1.25mm — because of the type of cells used and the specific arrangement of them. These batteries are constructed in a pouch with square cells rather than a square arrangement of round cells, which allows a higher number of cells to be packed into the space. This increases the capacity of the battery without increasing the size, making it an ideal option.

Combining high capacity with a slimline design makes Thin Cell technology ideal in several security applications, including sensors for home devices designed to detect motion. These sensors are ideally designed to be discreet, so the minimal footprint of a Thin Cell battery alongside a typical capacity of 1600mAh ensures that the sensors remain compact while offering power for extended periods of time.

Ensuring lasting connectivity
Of course, at the heart of these innovations in smart home battery technologies is a need for reliability and safety. Particularly in the case of primary CR123A batteries, cheaper options are common on the marketplace and may seem like a viable option to reduce design costs. However, these batteries are often cheaper at the expense of safety, reliability of supply and overall capacity and performance. In a home automation device where convenience is expected or in security systems where reliability is necessary, batteries or cells from untrusted suppliers are unsuitable.

For electronic design engineers, the best option is to partner with a trusted battery manufacturer such as Accutronics, who can ensure that standards of quality are maintained and that batteries deliver the performance needed. In addition, working closely with battery manufacturers also allows design engineers to ensure that the most suitable battery is specified.

Although many of us have grown accustomed to not giving second thought to battery selection in our domestic devices, that is quickly changing due to the rise of smart technologies. For now, the growing need for smarter batteries, built on engineering previously reserved for professional applications, means that electronic design engineers should always consider the battery as carefully as any other electronic component.