RF Wireless World

Browse articles, tutorials, tools, and vendors.

IoT Batteries: Primary vs Rechargeable Pros & Cons

By RF Wireless Expert Team

Introduction : One of the most critical decisions a hardware engineer must make when designing a new Internet of Things (IoT) device happens long before the code is written i.e. “How will this device be powered?”

While wired power is ideal, the vast majority of edge AI devices, smart home sensors and industrial asset trackers rely on wireless freedom. This leaves developers with two main choices viz. Primary (non-rechargeable) or Secondary (rechargeable) batteries.

Despite the global push for sustainability, primary batteries are not going away anytime soon. Certain environments and use cases simply cannot accommodate recharging. To make the best design choice, you need to understand the fundamental differences, the pros and cons of each, and how modern power management can stretch your device’s battery life to the absolute limit.

What are Primary Batteries in IoT?

Primary batteries are single use, non-rechargeable power sources. Once their chemical energy is depleted, they must be discarded and replaced. In the IoT world, these typically take the form of standard AA/AAA alkaline batteries, lithium coin cells (like the ubiquitous CR2032), zinc-air or LiMnO2 cells.

They are the go to choice for “deploy and forget” devices such as remote pipeline monitors, smart water meters or basic door/window sensors where the device needs to operate for years, but the cost or logistics of retrieving and recharging it is impossible.

Advantages of Primary Batteries

  • High Initial Energy Density: Primary cells pack a significant amount of energy into a small volume, often allowing low power sensors to run for 5 to 10 years without a battery change.
  • Extremely Low Self Discharge: Primary batteries hold their charge for years while sitting on a shelf or in a dormant device, making them perfect for emergency sensors (like smoke alarms) that spend 99% of their life asleep.
  • Lower Upfront BOM Cost: The batteries themselves are cheap, and the device doesn’t require the extra circuitry (charging ICs, USB ports) needed for recharging.

Disadvantages of Primary Batteries

  • Environmental Impact: Manufacturing a primary battery can take up to 50 times the energy it actually stores. Billions are discarded yearly, creating massive electronic waste.
  • Voltage Drop Off: As a primary battery depletes, its voltage steadily drops. Without proper voltage regulation, a device might shut down while there is still 30% or more usable energy left in the cell.
  • High Maintenance Costs: While the battery is cheap, sending a technician into the field to swap a battery in a remote agricultural sensor is highly expensive.

What are Rechargeable (Secondary) Batteries in IoT?

Rechargeable batteries can have their chemical reactions reversed by applying an electrical current, allowing them to be used hundreds or thousands of times. Common IoT chemistries include Lithium-Ion (Li-ion), Lithium Polymer (LiPo) and Lithium Iron Phosphate (LiFePO4).

These batteries are essential for devices with higher power demands (like wearables, smartwatches or cellular IoT asset trackers) or devices designed to work alongside ambient energy harvesting systems, such as small solar panels or kinetic energy scavengers.

Advantages of Rechargeable Batteries

  • Sustainability & Reusability: They drastically reduce battery waste and eliminate the need for physical battery swap maintenance if paired with an energy harvesting source.
  • High Peak Current Delivery: Rechargeables are much better at delivering the sudden, high power spikes required by Cellular IoT (LTE-M/NB-IoT) radios or Edge AI processing bursts.
  • Stable Voltage: Lithium-ion batteries maintain a relatively stable voltage profile throughout most of their discharge cycle compared to alkaline batteries.

Disadvantages of Rechargeable Batteries

  • Higher Self-Discharge: Rechargeable batteries naturally lose their charge faster than primary cells when not in use.
  • Hardware Complexity: Design of rechargeable batteries increase Bill of Materials (BOM) due to usage of charging circuitry, thermal protection and safety mechanisms to prevent overcharging or deep discharging.
  • Degradation: Over time and across hundreds of charge cycles, the total capacity of the battery degrades.

How to Optimize Power Management for Edge Devices

Whether you choose a primary coin cell or a rechargeable LiPo battery, inefficient hardware design can ruin your device’s lifespan. To get the most out of your batteries, engineers must look beyond the main System on Chip (SoC) and implement dedicated Power Management ICs (PMICs). Following points mention how we can optimize power for edge devices.

1. Extract Every Drop of Energy (For Primary Batteries)

Because primary batteries suffer from voltage drop as they drain, standard SoCs will often shut down prematurely because the voltage falls below their operating threshold. By using a PMIC with a highly efficient “Boost Regulator”, we can step up a dying battery’s low voltage (e.g. 0.7V) to a stable, usable voltage (e.g. 1.8V to 3.3V). This ensures to extract nearly 100 % of the stored energy before the battery is actually “dead.”

2. Implement “Ship” and “Hibernate” Modes

A massive amount of battery life is wasted while a product is sitting in a warehouse or on a delivery truck. Advanced PMICs feature ultra low current “Ship Modes” (drawing as little as 35 nanoamps). You can also utilize patent pending “break to wake” features or ultra low power wake up timers to keep the device in a deep hibernation state until the moment it is to be deployed by end user.

3. Use Highly Accurate Fuel Gauging

Users and network operators need to know exactly when a battery will die. Traditional voltage based measurement is often inaccurate. Modern PMICs integrate advanced fuel gauging algorithms that measure current flowing in and out of the battery, along with temperature and terminal voltage. By running this algorithm on the host SoC’s processor (e.g. Arm Cortex-M33) rather than dedicated hardware, you achieve precise battery life predictions without adding extra component costs.

4. Leverage Ambient Energy Harvesting (For Rechargeables)

If your device is deployed in a location with sunlight, thermal gradients or vibration, pair your rechargeable battery with an energy harvesting setup. Even a small solar panel can provide a trickle charge to your PMIC, effectively extending the device’s battery life from a few months to several years, completely changing the maintenance economics of your IoT deployment.

Conclusion

If your device requires high data throughput, cellular connectivity or operates in accessible/sunny areas, rechargeable batteries (especially paired with energy harvesting) are the future. However, for ultra-low cost, low maintenance sensors placed in dark, remote or indoor locations, primary batteries are the ultimate choice.

By pairing your chosen battery with a dedicated, highly efficient PMIC, you can ensure that no milliwatt of energy goes to waste.

Continue Learning IoT Basics, Architecture & Tutorials

Hardware: IoT Sensors, Actuators & SoCs

Real-World IoT Applications & Systems

Keep Reading

Related Posts