The landscape for remote wireless technology is changing rapidly. Innovative technologies are bursting on the scene, creating a technological explosion that is pushing the performance capabilities of consumer batteries to their limits, paving the way for a new generation of high-performance lithium batteries that can deliver long-term power solutions that enable maintenance-free operation for up to 40 years.
This market dynamic encompasses a wide range of industrial applications that are being utilized in remote locations where AC power is not available, thus necessitating a self-contained power supply for the entire operating life of the device. These applications include automotive toll tags, GPS tracking devices, scientific and oceanographic instruments, remote sensors, automatic utility meters, process controls, and other m2m devices.
Identifying the ideal power supply requires a fundamental understanding about the performance capabilities of both consumer and industrial batteries, including rechargeable and primary chemistries.
Consumer Rechargeable Batteries Keep Improving
Rechargeable battery technology is rapidly evolving from a consumer-based technology to a more broad-based technology that encompasses energy harvesting for industrial applications.
Consumer rechargeable batteries have come a long way since the Nickel Cadmium (NiCad) battery, which is large, has low energy density, and suffers from “memory effect” whereby a battery that is not fully depleted cannot be fully recharged. The introduction of the Nickel-Metal Hydride (NiMH) battery eliminated the “memory effect” problem common to NiCad batteries; however, NiMH batteries suffer from a high annual self-discharge rate, thus eliminating the potential for extended storage life.
Next came consumer-grade lithium ion (Li-ion) batteries, which gained popularity for their high efficiency and high power output. The most popular type of Li-ion cell, the 18650, was developed by laptop computer manufacturers as an inexpensive solution that could last approximately five years and 500 full recharge cycles. A common problem with consumer Li-ion cells is a gradual degrading of the cathode, which causes these batteries to become less receptive to successive recharging, and thus reduces battery life. These batteries are also made with crimped seals that are prone to leakage and corrosion.
Today’s slim profile smartphones and tablets are powered by thin lithium polymer batteries. Lithium polymer batteries can swell in size over time, have a limited operating life, and don’t work well in extreme temperatures.
Energy-Harvesting Apps Require Industrial-Grade Rechargeable LI-ion Batteries
Most energy-harvesting devices require long-term power that consumer rechargeable batteries cannot satisfy because they have an approximate lifespan of five years and 500 recharge cycles. This unmet need led to the introduction of TLI Series rechargeable Li-ion batteries.
Ruggedly constructed TLI Series batteries deliver up to 20 years of service life and 5,000 full recharge cycles, feature a very low annual self-discharge rate, the ability to be recharged in extreme temperatures (-40C to 85C), are capable of delivering up to 15A pulses from an AA-sized cell, and have a glass-to-metal hermetic seal to better withstand harsh environments.
The Choice Among Primary (Non-Rechargeable) Batteries
Consumer primary alkaline and consumer lithium batteries are everywhere, with billions of them manufactured each year for use in flashlights, remote controls, toys, and other consumer devices.
Alkaline cells are readily available and inexpensive, but suffer from low voltage (1.5V), a limited temperature range (-0C to 40C), a high annual self-discharge rate that limits life expectancy to two to three years, and crimped seals that are prone to leakage and corrosion.
Consumer primary lithium cells deliver 1.5V or 3V and were designed for camera flashes. These batteries have a narrow temperature range (-20C to 60C), a high annual self-discharge rate, and crimped seals, making them unsuited for many industrial applications.
Lithium thionyl chloride (LiSOCL2) cells are the preferred choice for remote wireless applications that require long-term power in extreme environmental conditions. Bobbin-type lithium thionyl chloride (LiSOCL2) chemistry is ideal because it offers the highest capacity and highest energy density of any lithium chemistry, along with an extremely low annual self-discharge rate (less than 1% per year), the widest possible operating temperature range, and a glass-to-metal hermetic seal.
Bobbin-type LiSOCL2 batteries can also be modified for extreme environments. For example, these batteries are being used to monitor frozen human tissue samples and organs being transported through the cold chain, where -80C temperatures need to be maintained, accomplished in part because bobbin-type LiSOCL2 cells are non-aqueous. These batteries can also withstand high temperatures of up to 150C. Bobbin-type lithium thionyl chloride batteries can also modified using patented hybrid layer capacitors (HLCs) or other means to deliver the high pulses required to power advanced communications.
However, not all bobbin-type LiSOCL2 batteries are created equal. For example, an inferior quality LiSOCL2 battery may deliver 10-year operating life with an annual self-discharge rate of 2% to 3% per year, while a superior-grade LiSOCL2 battery can feature a much lower annual self-discharge rate of 0.7% per year, thus permitting maintenance-free operation for up to 40 years.
As the shift in power swings toward industrial applications, advanced lithium battery technologies will fill in the performance gap that is unfulfilled by legacy consumer battery technologies.