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Choosing the Correct Battery Fuel Gauge for Your Project Needs

Justin Bickford
Written by Justin Bickford
Posted on January 16, 2024 at 8:41 AM

Battery fuel gauges are an essential component in today's world of mobile and portable devices. A battery fuel gauge acts as a battery pack's brain for efficient power management in electronic devices by providing accurate real-time data on the battery's state of charge (SoC) and state of health (SoH).

Fuel gauges allow for optimized power consumption, longer battery life, prevent over-discharge, and increased reliability and performance. At Epec, we can help you choose the correct fuel gauge for your project needs.

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How Fuel Gauges Work in Custom Battery Packs

From a technical perspective, a fuel gauge works by monitoring the battery's voltage, current, and temperature and then using this data to estimate the battery's remaining capacity and overall health. To accurately monitor these parameters, the fuel gauge must first be calibrated and properly configured. By setting key parameters for the gauge's operation, like voltage thresholds and low battery warnings, you can improve the end-user experience. Calibration helps ensure the fuel gauge measures the pack's voltage, current, and temperature without errors.

Custom battery pack with fuel gauge indicator

Custom battery pack with fuel gauge indicator.

Key Factors to Consider

Several key factors can help to sift through what fuel gauge is correct for your project. The main factors to focus on are the intended battery chemistry, application requirements, accuracy and precision, communication interface, and the integration and form factor.

Battery Chemistry

When dealing with different battery chemistries, there are a variety of fuel gauges that you can choose from. Other battery chemistries come with distinct characteristics, and your fuel gauge must be compatible with the specific chemistry you're working with. Understanding each chemistry's intricacies is essential to ensure accurate battery monitoring. Various chemistry types can impact the performance and longevity of your system.

Number of Battery Cells

You can significantly narrow your fuel gauge selection depending on your application requirements. Another major factor is the number of cells in the pack. Whether working with a single-cell or multi-cell configuration, your fuel gauge choice must align with the overall pack voltage and capacity requirements. Also, the load placed on the battery plays a prominent role. You must ensure the fuel gauge can accurately monitor the battery pack in its intended usage range.

Communication Protocol

Another critical factor to remember is the communication protocol used by the overall system. Standard protocols include I2C, HDQ, SPI, and One-Wire. Most TI fuel gauges will support I2C, HDQ, and SPI fuel gauges, while Maxim fuel gauges typically support One-Wire and I2C, depending on the gauge.

Methods Of Measuring

Fuel gauges also have three main methods of measuring the batteries' state of charge. Those three methods are coulomb counting, voltage-based, and hybrid fuel gauges.

Coulomb Counting Fuel Gauge

Coulomb counting fuel gauges are some of the most fundamental fuel gauges available. They allow for a high precision state of charge estimate and are less affected by the self-discharging of cells within a battery. However, they require precise calibration to be reliable and can accumulate minor errors over time that lead to inaccuracy during the end of the battery pack's life cycle.

Voltage-Based Fuel Gauge

Voltage-based fuel gauges are some of the simplest on the market. These rely on monitoring the battery voltage to estimate the remaining state of charge. Typically, these gauges consume minimal power and are suitable for simple fuel gauging scenarios.

These generally are less precise than coulomb counting gauges and may take inaccurate readings while the battery is under load. Voltage-based fuel gauges are most accurate when the batteries have had time to rest after being under load or charging.

Hybrid Fuel Gauge

The final type of fuel gauge is a hybrid gauge. These typically combine multiple measurement methods and are the most accurate of the three gauges. They are the most common type of fuel gauge available on the market today. They perform their monitoring using a combination of coulomb counting, voltage monitoring, and temperature sensing to provide a more comprehensive view of battery health. These typically are more robust and fluctuate less with variations in battery health over time.

The Heart of Most Systems

In the modern world of electronic devices, fuel gauges serve as the heart of most systems, ensuring that portable devices can operate smoothly. These components provide:

  • Real-time data on the battery's state of charge and health.
  • Contributing to optimized power consumption.
  • Extending battery life and reliability.

As you are looking to select the correct fuel gauge for your project, remember that the choice you make can impact the device's performance and longevity. It is essential to factor in the battery chemistry, application requirements, communication protocols, and the measurement method needed in your system.


Ultimately, the success of your project relies on making a well-informed, thought-out decision on what battery fuel gauge to use. You can confidently narrow down the selection by evaluating and weighing the abovementioned factors against the project requirements. Whether developing a new project or updating an existing one, the correct fuel gauge ensures you get the most battery life out of your battery and provides a seamless end-user experience.

Topics: Battery Packs

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