This charger can power compact IoT devices

The challenges of small batteries

With the notable exception of the large lead-acid batteries used in cars, batteries have spent the last few decades getting smaller and more efficient. What started as a massive battery pack in mobile phones of the early 1990s – that would often only work correctly when plugged into the vehicle’s cigarette lighter – has evolved into small lithium-based batteries that can easily fit in the palm of your hand while still providing days’ worth of power for your average device.

Smaller batteries, such as the rechargeable options in wireless earbuds or fitness trackers, can last for days or weeks but use significantly less voltage to charge. Most cell phone chargers, for example, convert the 120 or 220 volts (depending on your location) power coming from the socket down to 5 to 12 volts. This allows you to charge your battery without burning it out.

Smaller batteries use even less voltage, such as those mentioned above. The thin, high-density, rechargeable batteries you might find in a fitness tracker or a pair of AirPods use between 2 and 3 volts for their standard charge. With most wireless chargers designed for phones – and charging at 5 or more volts – this can create a problem that results in battery failure much faster than the manufacturer may have anticipated.

A new evaluation board

Currently, there are no battery chargers on the market capable of handling the more comprehensive voltage range necessary to keep these devices charged. That’s where Rohm Semiconductor – a Japanese tech company that opened its doors in 1958 – comes in. Rohm Semiconductor designed a new battery charger integrated circuit (IC) specifically programmed for those small, solid-state rechargeable batteries.

Instead of sticking to a single higher voltage as most wireless phone chargers do, this battery charger IC supports low voltage charging between 2 and 4.7 volts. The user needs to change the external resistor, increasing or decreasing the design load when changing batteries. It sounds like an extra step, but it can help improve the battery life of these small devices without worrying about overcharging.

In addition to the variable charging capacity, these battery charger ICs are much smaller than previously available options. The package measures 0.4mm thick, making it 60% smaller than comparable packaging in existing chargers.

The risk of overcharging

Pumping too much energy into your mobile device batteries doesn’t just make your phone uncomfortably warm or your earbuds discharge that much faster. Trying to charge an IoT device on a charger that generates too much electricity or that isn’t designed for your machine can result in significant damage.

In the best-case scenario, the battery will lose some of its charging capacity. Regardless of their size or type, batteries have a limited lifespan and a set number of charging cycles. Once the battery reaches the end of its lifespan, it will simply stop holding a charge.

Overcharging can cause the battery to expand or even catch fire in the worst-case scenario. This problem is rare, but it can be dangerous, especially with lithium-ion batteries. The lithium metal in these batteries is incredibly volatile when exposed to air. It doesn’t take much to ignite it.

Applications for small IoT devices

Where could we see this sort of ultra-thin charging changing the IoT industry in the future? The applications are nearly endless due to the slim and modular nature of Rohm Superconductor’s charging system.

The IoT market is growing exponentially. Experts estimate that spending on IoT devices and related hardware will hit $1.2 trillion in 2022. The industrial IoT (IIoT) was worth $77.3 billion in 2020 and could be worth as much as $110.6 billion by 2025.

IoT devices are becoming invaluable tools in any number of industries. Wastewater treatment plans can use small sensors to detect water movement through pipes or take samples for remote analysis. In the manufacturing sector, these devices can act as sensors to monitor equipment health, detect employee proximity to improve workplace safety, or perform a million other simple tasks that can help keep the operation running smoothly.

Wearable IoT devices such as fitness trackers are popular with a large segment of the population, especially ones that offer additional features such as messaging. In an industrial setting, wearable IoT devices can detect fatigue in equipment operators, which can help prevent accidents in the workplace.

These are only a few examples of possible applications for small IoT devices. All of these examples have a rechargeable battery and the need for easy and efficient charging tools that don’t overcharge the device. Rohm Superconductor’s charger fits the bill and could potentially change how we think about charging devices, both large and small.

Creating a networked future

The Internet of Things is swiftly becoming part of our daily lives, and each of these tiny networked devices will need a battery to keep them running and a charger to keep that battery powered. Instead of hard-wiring every IoT device in your home or business into the building’s power grid, low-voltage slim chargers like the one Rohm Superconductors is rolling out can keep everything charged and ready to go.

With existing technology, we can’t yet create perpetually powered IoT devices – although some researchers are making inroads there. For now, efficient chargers and long-lasting batteries are our best options. Regardless of the battery or charging method you choose, we’re well on our way to creating a fully networked future, which will be an exciting thing to see.