Battery Power Tips

  • Home
  • Markets & Applications
    • Automotive
    • Aerospace & Defense
    • Energy Management & Harvesting
    • Industrial
    • IoT
    • Medical
    • Renewables & Grid Connected
    • Robotics
    • Stationary Power
    • Wearables
  • Learn
    • eBooks/Tech Tips
    • EE Training Days
    • FAQs
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • R&D
  • Resources
    • Design Guide Library
    • Digital Issues
    • Engineering Diversity & Inclusion
    • LEAP Awards
    • White Papers
  • Engineering Training Days
  • Advertise
  • Subscribe

When to use energy harvesting and when to use long-life batteries

By Jeff Shepard | March 1, 2023

Energy harvesting (EH) can be an attractive way to power wireless internet of things (IoT) and other small devices. EH can be combined with rechargeable batteries, capacitors, or supercapacitors to enhance performance. Depending on the circumstances, primary batteries can provide a more reliable and even lower-cost option. This FAQ looks at ways to classify EH sources, considers the advantages and drawbacks of EH, presents long-life primary batteries as an alternative to EH, and closes by reviewing the challenges associated with powering high-pulse power loads like remote actuators and data-intensive two-way radio communications.

What EH to use?

The energy source, or type of EH, is an important factor that determines availability, reliability, and cost. EH devices can derive their power from external or ambient energy sources, as depicted in Figure 1. Artificial energy such as machine vibrations, heat, or pressures from manufacturing operations and human activities are all external sources. Ambient energy sources include naturally occurring energy like wind, solar, etc. The type of EH has important implications for energy availability, reliability, and cost.

Figure 1. EH technologies can be classified by whether the source of energy is from the ambient environment or an external source (Image: Nanoprecise).

With few exceptions, like bright sunlight for higher power or ambient RF energy for low power, the sweet spot for EH applications lies in the microwatts (µW) to milliwatts (mW) power range, with typical energy densities of about 100 µW/cm2, as shown in Figure 2. Consider a common CR2032 lithium manganese dioxide (LiMn02) non-rechargeable coin cell as a starting point for EH versus battery comparisons. It has a nominal voltage of 3.0 V, a capacity of about 235 mAh, and can provide 1 mW for only about 2 days, but if the power demand drops to the µW level, that same coin cell can last 4 years — quite a difference. Coin cells can provide a lower-cost alternative to EH for very low-power applications with limited operating lifetimes.

Figure 2. EH can be best suited for applications that consume microwatts to a few milliwatts of power (Image: Force Technology).

Another factor is that EH is not generally the most compact solution. Physics often conspires against EH in this area. EH systems must accommodate a combination of low densities of available energy and low conversion efficiencies. As a result, providing significant amounts of power from thermal, vibration, and other sources of ambient energy can require a bulky solution compared to a battery.

EH is not free

EH sources are freely available, but EH systems are not free. In fact, they can cost more than battery power. Determining when to use EH and when to use batteries requires detailed and thoughtful analysis.

Specifying a battery power source is a straightforward exercise in analyzing system power requirements. Not so for EH, where analyzing system power needs is only the first step. Designing an EH source requires that the source be thoroughly analyzed in the actual operating environment, including any changes anticipated for that environment during the operating life of the powered device. The peak power capability of the EH device will often not be realized in actual installations. Developing a detailed model or database of the anticipated available energy levels over time can be necessary. How reliable will it be? How will the conversion efficiency of the EH device vary as it ages or for differing available energy levels? What are the power management needs?

Power management

Power management needs can differentiate between using a battery or an EH power source. Power management for a battery-powered system can be a simple regulator to account for any voltage variations (usually declining voltage) as the battery is discharged. Power management for an EH system is more complex and potentially more costly. EH devices often require maximum power point tracking to produce the maximum output. Energy storage devices in a solar EH system can also require overcharge protection due to the unpredictability of solar energy.

What type of energy storage will be required for systems with peak load needs? What charge management is required? The initial hardware and design cost for an EH system can be much larger than a battery-powered solution. For example, if multiple supercapacitors are used for energy storage, they require additional cell balancing circuits, further increasing system size, weight, cost, and consumption of valuable energy.

On the other hand, battery replacement costs need to be factored into the comparison. Battery replacement can be minimized by using a larger battery or a more environmentally rugged battery, but both options come with increased costs.

Energy storage device tradeoffs

Li-ion rechargeable batteries offer a combination of good energy density and environmental ruggedness that suits them for pairing with EH devices, as shown in Figure 3. Lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminum oxide (NAC) rechargeable chemistries offer nominal voltages of about 3.6 V and can be recharged 1,000 or more times. Supercapacitors can provide higher power densities compared to Li-ions. They can be suitable for EH support in applications that require thousands or tens of thousands of charge and discharge cycles.

Figure 3. The energy densities of battery chemistries can vary by up to 100x (Image: ResearchGate).

EH is usually associated with rechargeable energy storage like Li-ion batteries and supercapacitors, but it can also be used with primary batteries. If an application needs infrequent pulses of power and a long operational life, primary batteries can be paired with EH. The EH, together with a small capacitor, can provide continuous levels of power for sensors or housekeeping, and a primary lithium battery can provide peak power needs and support long operational life.

Primary batteries are tried and true

Compared with EH choices which are mostly niche technologies, primary batteries are a mainstream option. Lithium-thionyl chloride (Li-SOCl2, or LTC) is particularly well-suited as a long-term power source for wireless IoT nodes. Bobbin-style LTC batteries offer an operating temperature range from -40 to +85 °C, high capacities, an operating voltage of 3.6 V, and very low self-discharge rates, making them particularly suitable for providing long-term (20 years or longer) power for wireless IoT nodes. Some battery makers can provide data on self-discharge rates over various temperatures, pulse power capabilities, and other data needed to determine a battery’s operating life for a specific design, like the example in Table 1 below.

Table 1. Design example of a 20-year life from a AA-sized LTC battery for a wireless IoT node  (Table source: Tadiran Batteries).

Power pulses and transient minimum voltage

Industrial IoT (IIoT) devices can also require high-power pulses of several amps. Higher than can be delivered by a standard LTC battery. The challenge with using a bobbin-style LTC battery to deliver high pulses is the temporary drop in the voltage delivered by the battery. The voltage returns to its nominal value after experiencing a transient minimum voltage (TMV) that can disrupt system operation. That can be addressed by using a spiral-type LTC battery that can deliver higher power pulses but at the cost of lower capacity and shorter operating life.

A hybrid device that combines a bobbin-style LTC battery with a hybrid layer capacitor (HLC) can be used. The battery delivers the high capacity needed to support long operating life. The HLC can support periodic high-power pulses for functions like actuators or longer-distance two-way RF communications. The voltage curve of the hybrid device experiences a plateau near the end of life that can be monitored by the system and used to issue a low battery alert.

An alternative way to address TMV is to use supercapacitors. Supercapacitors tend to have limited temperature ranges, making them less suitable for industrial applications or remote wireless IIoT nodes, and they are bulky with high self-discharge rates. When adding any capacitor in parallel to a battery, it’s important to consider the combined self-discharge of the battery and capacitor system. While supercapacitors have high self-discharge rates, the HLC can be designed with a low rate of self-discharge, matching the self-discharge rate of the LTC battery and producing a long-life hybrid energy storage device.

Summary

EH can be an effective power source in a range of niche applications that require very low levels of power or can accommodate a large and inefficient power source. While the ambient energy to be harvested can be free, an EH system entails significant upfront costs in design and installation. Long-life primary batteries can provide a cost-effective and compact alternative to EH in many mainstream applications.

References
Batteryless Electronics, Force Technology
Energy Harvesting for IOT – Status and Evaluation, Nanoprecise
Lithium Batteries for Wireless Sensor Networks, Tadiran Batteries
Next-Generation IoT Devices: Sustainable Eco-Friendly Manufacturing, Energy Harvesting, and Wireless Connectivity, IEEE Journal of Microwaves
Power Versus Energy When Designing Smart Wireless Devices, International Society of Automation

You may also like:


  • Why self-discharge is important in batteries

  • How scanning electron microscopy is helping researchers develop better lithium-ion…

  • Need a really long-life battery or heat? Try a radioisotope…

  • When does DC coupling maximize the performance of battery storage…

  • How tiny solid-state batteries enable smaller implants that recharge faster

Filed Under: Batteries, Battery Management, Capacitors, Energy Management & Harvesting, FAQs, Featured, IoT, lithium-ion, Power Management
Tagged With: Force Technology, Nanoprecise, Tadiran Batteries
 

Next Article

← Previous Article
Next Article →

“battery
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.

Featured Contributions

  • Preparing for sodium-ion battery storage? Advanced simulation models can help
  • Q & A: why automation is essential for advancing EV battery manufacturing
  • Battery and charging innovations driving electrification
  • What is a lithium battery digital passport?
  • Battery testing: critical to the rise of electric vehicles
More Featured Contributions

EE TECH TOOLBOX

“ee
Tech Toolbox: 5G Technology
This Tech Toolbox covers the basics of 5G technology plus a story about how engineers designed and built a prototype DSL router mostly from old cellphone parts. Download this first 5G/wired/wireless communications Tech Toolbox to learn more!

EE LEARNING CENTER

EE Learning Center

ENGINEERING TRAINING DAYS

engineering

RSS Current EDABoard.com discussions

  • How to transfer usb cdc data using DMA? (stm32f407)
  • How to create custom diode and add its netlist into Ansys circuit designer schematic?
  • MoM capacitor at 36 GHz
  • How to find the resonance frequency and impedance of a planar spiral coil in HFSS?
  • Collector Current Low side Has a large drop respect High Side during Miller during Double Pulse Test
“bills
Battery Power Tips
  • EE World Online
  • Design World
  • Medical Design & Outsourcing
  • Solar Power World
  • The Robot Report
  • Contact
  • Sign Up Enews

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search Battery Power Tips

  • Home
  • Markets & Applications
    • Automotive
    • Aerospace & Defense
    • Energy Management & Harvesting
    • Industrial
    • IoT
    • Medical
    • Renewables & Grid Connected
    • Robotics
    • Stationary Power
    • Wearables
  • Learn
    • eBooks/Tech Tips
    • EE Training Days
    • FAQs
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • R&D
  • Resources
    • Design Guide Library
    • Digital Issues
    • Engineering Diversity & Inclusion
    • LEAP Awards
    • White Papers
  • Engineering Training Days
  • Advertise
  • Subscribe