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In today's world of ubiquitous mobile devices, a low-battery notification can often feel like the digital equivalent of running out of gas on a deserted highway. Thankfully, portable power banks have come to the rescue, ensuring our devices stay powered when we need them the most.

Full disclosure: I wasn't immediately sold on portable power banks. In their early days, they seemed limited, catering to specific devices, limited in port offerings, or lacking the capacity to charge multiple gadgets simultaneously. Furthermore, their charging speeds were often underwhelming, with the units requiring several hours for a full recharge. Plus, the challenge of compatibility with varying power delivery standards was daunting. However, with advancements in technology, today's portable power banks have addressed these concerns, transforming them into indispensable tech marvels.

But what exactly has contributed to the impressive rise and excellent performance of these compact energy reservoirs? I believe it’s the result of a perfect storm: the fusion of advanced battery technologies, groundbreaking Gallium Nitride (GaN) chargers, efficient power delivery (PD) designs, and the widespread acceptance of USB-C^™, all supported by economies of scale.

Take, for example, the Anker 737 PowerCore 24K Series 7 power bank, which I recently purchased (Figure 1). This 630g portable power bank is Power Delivery (PD3.1) and Quick Charge compliant and features six 4,000 milliampere-hours (mAh) lithium-ion (Li-Ion) cells for a 24,000mAh power bank capacity, equivalent to 86.4 watt-hours (Wh), which puts it nicely below the 100-watt FAA allowable limit for air travel.

Thanks to GaN, the Anker 737 power bank features 140W high-speed output discharge capabilities. This power bank is designed for optimal convenience and speedy performance in a sleek, compact design. It boasts real-time temperature monitoring and universal device compatibility to ensure your mobile gadgets stay powered without a hitch. With robust charging capacities through two USB-C ports (140W maximum output each) and one USB-A port (18W maximum output), it can simultaneously energize three devices or enable pass-through charging for two devices while replenishing its own battery. Simply plug your cell phone, laptop, camera, or other gadgets into the power bank and connect it to the power source. This power bank outshines even the latest cell phones in recharge speed, boasting a formidable 140W recharging capability that soars from 0% to 100% in under an hour, storing more than 4X the charging potential of the latest flagship cell phones.

Figure 1: The Anker’s 737 140W output can charge power-hungry devices like a MacBook Pro 16-inch as effortlessly as charging a smartphone or earbuds. (Source: Author)

Li-Ion Batteries: The Heart of the Power Bank

At the heart of every power bank lies its battery technology. Li-Ion batteries have become the industry standard due to their high energy density, long cycle life, and decreasing costs. They pack a lot of power in a small space, making them ideal for portable applications. As technology and manufacturing processes have improved, the cost of producing these batteries has reduced significantly, making high-capacity power banks more affordable for the masses.

Gallium Nitride (GaN) chargers have transformed the way we think about charging speeds. GaN is a next-generation semiconductor material that offers greater efficiency and can handle higher voltages than traditional silicon chargers. This translates to faster charging times and compact charger designs, ensuring your power bank recharges rapidly and is ready to go when you are.

Fast Power Delivery (PD) is a game changer, allowing devices to charge at optimized speeds safely. Combined with the pervasiveness of the USB-C port—now found on most modern smartphones, tablets, and laptops—users can enjoy a standardized, high-speed charging experience across multiple devices. This simplifies the charging ecosystem, ensuring that one power bank can serve a variety of electronic needs.

As demand for power banks has surged, large-scale manufacturing processes have evolved to meet the demand, resulting in economies of scale. This has made it feasible for companies to produce high-quality power banks at truly competitive prices, making them accessible to a larger segment of the population.

With great power comes great responsibility. The increased energy densities of Li-Ion batteries come with risks, such as thermal runaway—a chain reaction within the battery that can lead to overheating and potential explosions. The Battery Management System (BMS) is an unsung hero in this narrative. It monitors and controls the charge and discharge of the battery, ensuring it operates within safe parameters. The BMS also manages the battery's temperature, protecting it from potential hazards and ensuring longevity.

Given the inherent risks of Li-Ion batteries, organizations like the FAA have taken note. To ensure the safety of air travel, the FAA has imposed limits on the transport of spare (uninstalled) Li-Ion and lithium metal batteries, including power banks. Li-Ion rechargeable batteries are limited to a rating of 100 Wh per battery. These limits allow for nearly all types of Li-Ion batteries to be used by the average person in their electronic devices.

This week’s New Tech Tuesday features two key devices that help keep Li-Ion power banks safe for air travel.

The Texas Instruments BQ25756 is a versatile bidirectional buck-boost battery charge controller tailored for Li-Ion, Li-polymer, and LiFePO4 chemistries, spanning a vast 4.2V-70V input voltage and up to 70V battery voltage. Its standout features include 1-14 cell Li-Ion and 1-16 cell LiFePO4 support, a synchronous buck-boost controller with adjustable frequencies from 200kHz to 600kHz, and an integrated loop compensation with soft start. With bidirectional power support, the device efficiently manages charging, ensuring ±0.5% charge voltage accuracy and ±3% precision for both charge and input current regulations. Furthermore, its reverse mode aligns with the USB-PD EPR power profile, offering adjustable voltage (3.3V-65V) and current (400mA-20A) regulations. Designers will appreciate the ease of I²C control with resistor-programmable options, bolstered by a 16-bit ADC for comprehensive monitoring. Ensuring device and battery safety, it integrates overvoltage, overcurrent, battery short, and thermal shutdown protections. Informative status indicators provide real-time feedback, all packaged compactly in a 36-pin 5mm x 6mm QFN.

Next, Vishay / BC Components' AEC-Q200-Qualified NTC SMD Chip Thermistors are designed for precision, offering a wide temperature range of -55°C to +150°C. As negative temperature coefficient (NTC) thermistors, they excel in temperature compensation, sensing, and protection across diverse sectors, from automotive to consumer electronics. The NTCS series stands out for its robust construction and reliability in thermal cycling environments, suitable for both PCBs and flexible circuits. These thermistors utilize bulk ceramic technology and are available in standard surface-mount sizes: 0402, 0603, and 0805. They boast a high sensitivity, resistance values at 25°C from 1KΩ to 680KΩ, and beta values ranging from 3370K to 4125K. Moreover, they are RoHS compliant, cULus recognized, and can seamlessly integrate into high-volume, automated manufacturing processes. Key applications include battery management, automotive systems, consumer electronics, and medical devices.

In an era dominated by mobile devices, portable power banks have emerged as essential tools to prevent our gadgets from running out of power. Despite initial limitations, advancements in battery technology, the integration of Gallium Nitride chargers, and the adoption of universal USB-C have significantly improved their functionality and efficiency. Furthermore, economies of scale have made these tech wonders affordable for many. Technologies like the Texas Instruments BQ25756 and Vishay / BC Components' NTC SMD Chip Thermistors further enhance battery safety and efficiency. Ultimately, today's power banks are a testament to technological progress, ensuring our devices are always powered and ready to match the pace of our fast-moving world.

Sources:

“Portable Power Bank Market Report Overview.” Business Research Insights, October 16, 2023. https://www.businessresearchinsights.com/market-reports/portable-power-bank-market-103127.