IoT data acquisition devices run on electricity. Consequently, a reliable power source is as much of an enabler as the well-crafted marketing perception, that wireless IoT networks transporting data are crucial. While laptops and cell phones can conveniently be carried out around, at the end of the day they usually end up plugged-in for recharging. What happens to a device which must operate in a remote location, uninterruptedly and unattended for months, even years, away from any electrical grid? In this common case, the best choice is— batteries. Reliable batteries.
Batteries – a Well-deserved and Overdue Attention
Being a single point of failure, a well-deserved and overdue attention must be paid to batteries. Battery size relates to operational life: the bigger—the better. However, chemistry is what actually defines battery capability. Here is a list of most common commercially available battery types divided by chemistry:
- Carbon-Zinc
- Ni-Cd
- Ni-MH
- Alcaline
- Acid
- Lithium
- Li-Ion
- Li-Po
Cost is a major differentiator and for a good reason.
Carbon-Zinc Batteries
Availability – 3/5
Energy Storage – 2/5
Cost – 2/5
One of the oldest types around. Non-rechargeable. Low energy storage capabilities and very low-cost. Not recommended for long-term or critical applications.
Ni-Cd (Nickel Cadmium), Ni-MH (Nickel Metal-Hydride) Rechargeable Batteries
Availability -3/5
Energy Storage – 3/5
Cost – 2/5
Used primarily is some power tools due to their capability for high output current. Not the best choice for long-term operation because of a relatively high self-discharge current and low nominal voltage. Poor performance in subzero temperatures. Nickel-based batteries do not show any considerable advantage and are being replaced by Lithium-based technology.
Alkaline Batteries
Availability – 5/5
Energy Storage – 3/5
Cost – 1/5
Non-rechargeable (in their most common versions). A golden standard for powering consumer products. These batteries come in a variety of standardized sizes. Reliable and enduring to cold and hot conditions they are considered a proven and safe technology. An excellent compromise between performance and cost although not a first choice in fully automated long-term operating equipment due to low nominal voltage.
Acid Batteries
Availability – 4/5
Energy Storage – 2/5
Cost – 3/5
The benchmark chemistry in the automotive industry. A proven, rechargeable, heavy-duty technology for high output current and reliability, enduring extreme weather conditions. Downside – low capacity and heavy weight make acid batteries virtually unusable in handheld and small form-factor equipment.
Lithium Non-rechargeable Batteries
Availability – 2/5
Energy Storage – 5/5
Cost – 5/5
Standard industrial chemistry. Unsurpassed energy density among all battery types. With its light weight and high capacity, a single Lithium non-rechargeable cell can easily provide—under extreme environmental conditions—months of uninterrupted operation for a low-power electronic equipment. These batteries are characterized with very low self-discharged current which additionally extends their long life. Lithium non-rechargeable batteries are manufactured in variety of form-factors including the same standardized shapes as the Alkaline batteries. The best choice is in use cases of industrial automation and applications where long device autonomy is crucial. More expensive than any battery listed above and not readily-available on the consumer market. Due to the toxic chemistry and powerful electrical properties all Lithium-based batteries (including Li-Ion and Li-Po) are considered hazardous goods and restrictions to their transportation have been imposed by IATA.
Li-Ion (Lithium-Ion) and Li-Po (Lithium-polymer) Rechargeable Batteries
Availability – 3/5
Energy Storage – 4/5
Cost – 4/5
The most universally applicable batteries in the consumer electronics of today. Sharing the advantages of their non-rechargeable counterparts – the Li-Ion and Li-Po batteries – they evolved to provide higher discharge currents and safer operation. These batteries are the best choice if long life, high reliability and low maintenance cost in the long run is required. While suitable for discharge in subzero conditions, these chemistries must only be recharged under positive temperatures. The Li-Ion batteries are the industrial standard rechargeable power source taking over the older Ni-Cd and Ni-MH technologies. The extremely light weight, the abundance of form factors, as well as the short recharge time of Li-Po cells makes them suitable for portable, hand-held and small data acquisition devices.
Warning: observe polarity of Li-Ion battery. Due to safety reasons most Li-Ion 18650 batteries are designed with almost flat positive electrode.
Energy harvesting Solutions
Solar panels remain a viable option. The effective area of a solar panel can in time be reduced by a layer of dust, snow, contaminants or heavy clouding, as well as angle of installation and the cyclic change of seasons. A careful calculation of energy margin is crucial to ensure sufficient power under all conditions. Other energy harvesting solutions such as portable, wind and wave driven generators, temperature-to-electricity or vibration converters can be used in non-critical applications. Unpredictability (wind, vibration) and cyclic operation (solar, thermal) are two of the major drawbacks for low reliability of energy harvesting solutions. On a positive note, all these energy sources are free. Therefore, they can back up batteries to create an elegant and long-lasting solution to the ever-present energy hunger.
At Evvos, we understand the principle limitations of batteries. Our devices support several power supply options, including low-cost alkaline, high-capacity Lithium and universal, rechargeable Li-Ion batteries. External power options also extend the range of energy harvesting solutions and increase the autonomy of our products.
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