Industrial grade lithium batteries provide the on-demand power required to expand digital connectivity into remote locations and extreme environments.
On the fast lane to becoming a multi-trillion-dollar industry, the Industrial Internet of Things (IIoT) has ushered in the age of Industry 4.0, where manufacturing and industry increasingly rely on smart data and analytics to deliver more intelligent decision-making.
At the heart of the IIoT and Industry 4.0 are lithium battery-powered devices that operate in extreme environments, enabling AI on the edge, machine-to-machine (M2M) communication, machine learning, and other advanced technologies to expand almost limitlessly without the need for expensive hard-wiring.
Battery-powered devices serve to capture, exchange, store, analyze, and apply data more intelligently to improve operational efficiencies, identify problems, enhance quality control, track assets, promote greater environmental sustainability, optimize supply chains, enhance field service, and initiate predictive maintenance programs that save time and money and reduce downtime. Popular applications include supervisory control and data acquisition (SCADA), process control, industrial robotics, asset tracking, safety systems, environmental monitoring, M2M, AI, and wireless mesh networks, to name only a few. Lithium batteries are at the heart of this digital transformation.
Specialized batteries are required for long-term deployments
To support long-term deployments, the ideal power source must be capable of operating for extended periods without having to replace the battery. To conserve energy, these devices need to employ low-power chipsets, low-power communications protocols (i.e., WirelessHART, ZigBee and LoRa), and proprietary techniques aimed at minimizing energy consumption during ‘active’ mode. While beneficial, these energy-saving techniques are dwarfed by the choice of battery.
Numerous primary battery chemistries are available, each offering unique advantages and disadvantages. At one end of the spectrum are consumer alkaline cells that deliver high continuous current but suffer from very high self-discharge rates (up to 60% per year) that make them generally unsuited for long-term deployments. Alkaline cells have low capacity and low energy density, which adds size and bulk. These cells also contain water-based constituents that are more likely to freeze, thus limiting their use to indoor settings and moderate climates.
On the opposite end of the spectrum are lithium-based chemistries. As the lightest non-gaseous metal, lithium features an intrinsic negative potential that exceeds all other metals, delivering the highest specific energy (energy per unit weight), highest energy density (energy per unit volume), and higher voltage (OCV) ranging from 2.7 to 3.6V. Lithium cells are also non-aqueous and therefore less likely to freeze in extremely cold temperatures. Among lithium primary batteries, bobbin-type lithium thionyl chloride (LiSOCl2) chemistry is overwhelmingly preferred for remote wireless applications. Bobbin-type LiSOCl2 chemistry delivers the highest capacity, highest energy density, an extended temperature range (-80°C to +125°C), and an incredibly low self-discharge rate (less than 0.7% per year for certain cells). The benefits of this chemistry include higher reliability, long operating life (up to 40 years), wider temperature range, higher energy density, and higher voltage.
Bobbin-type LiSOCl2 cells were specifically developed for use with devices that draw average current measurable in micro-amps with pulses in the multi-amp range. Meanwhile, niche applications are also arising that require milli-amps of average current with multi-amp pulses, drawing enough average energy to prematurely exhaust a primary (non-rechargeable) battery. These specialty applications often require an energy harvesting device in combination with an industrial grade rechargeable Lithium-ion (Li-ion) battery to store the harvested energy and generate high pulses.
Low battery self-discharge increases return on investment
Every battery suffers from some amount of self-discharge, as chemical reactions continually drain current even while the cell is not being used or is disconnected. This problem is especially acute for devices intended for long-term deployment that operate mainly in a ‘standby’ mode, where more energy can be lost annually as a result of self-discharge than is required to operate the device.
Bobbin-type LiSOCl2 cells are uniquely designed to minimize self-discharge by harnessing the passivation effect. Passivation occurs when a thin film of lithium chloride (LiCl) forms on the surface of the lithium anode, separating it from the electrode to greatly reduce the chemical reactions that lead to high self-discharge.
Leading battery manufacturers have developed ways to maximize the passivation effect. As a result, top quality bobbin-type LiSOCl2 batteries can have a self-discharge rate as low as 0.7% per year, retaining nearly 70% of their original capacity after 40 years. By contrast, lesser quality bobbin-type LiSOCl2 cells can have an annual self-discharge rate as high as 3% per year, exhausting roughly 30% of their available capacity every 10 years, which severely limits their operating life.
High pulses drive two-way communications
To support two-way wireless communications and other forms of connectivity over public and private networks, a remote battery-powered device can require high pulses of up to 15A to support data queries and transmission. Standard bobbin-type LiSOCl2 cells cannot deliver high pulses due to their low-rate design. This challenge can be easily solved with the addition of a patented hybrid layer capacitor (HLC).
Under this hybrid approach the standard bobbin-type LiSOCl2 cell delivers low-level background current during ‘standby’ mode while the HLC delivers the high pulses needed to power two-way wireless communications and other advanced functionality. The patented HLC also features a unique end-of-life voltage plateau that can be interpreted to deliver ‘low battery’ status alerts to support predictive maintenance programs that reduce downtime.
Remote wireless devices benefit from long-term solutions
With any long-term deployment, it obviously reasons that the ideal battery-powered solution should last for the entire lifetime of the device to reduce or eliminate the need for costly battery change-outs.
Unfortunately, a lower quality battery with an elevated self-discharge rate may be hard to distinguish since the cumulative annual capacity losses may take years to become fully measurably. Additionally, the theoretical models and algorithms used to calculate expected battery life can be highly unreliable since they tend to underestimate the passivation effect as well as long-term exposure to extreme temperatures. As a result, careful due diligence is required when specifying batteries to ensure a robust solution: a process
that begins by demanding all potential battery suppliers to supply fully documented and verifiable test results along with in-field performance data under similar loads and environmental conditions.
Wireless technology is spreading everywhere, and industrial grade ultra-long-life primary and rechargeable Li-ion lithium batteries are playing a central role in providing the longevity and high pulse energy required for high-speed IIoT connectivity.