Feature: Software & tools
profitable. Terefore, testing and predicting a device's battery life is more important than ever and determining precise current consumption is crucial. For this, system developers use emulation and profiling soſtware.
Battery profiling software Tere are several reasons why battery profiling and characterisation are essential. Users must know how much energy the battery can hold and deliver as it drains over time. Te open circuit voltage (VOC) and internal resistance (IR) change as the battery drains. Tese need to be plotted so that the profile shows the actual performance of the real battery; see Figure 1. Verifying the battery's performance under certain discharge
Emulation and profiling software for optimising IoT device battery life
By Andrew Herrera, RF and IoT expert, Keysight
I
nternet of Tings (IoT) devices are today found in many applications, from consumer and medical to industrial. Being small and battery-powered, their battery life is an essential part of quality and safety, as well as customer satisfaction. In medical devices, for example, the implantable types must be extremely safe and robust, which also depends
on battery performance. When battery life falls short of expectations, the device can become dangerous for patients. Battery life is also crucial in intelligent city applications
and asset tracking. Here, IoT devices also need long-lasting batteries, as changing them over a large deployment area is not
22 September 2024
www.electronicsworld.co.uk
conditions and operating modes is also essential. Among the factors influencing battery behaviour are temperature, load current profiles (constant/dynamic) and different operating modes, including constant current, power and resistance. Since battery life depends on all these parameters, creating different battery profiles that suit specific discharge situations is essential. By using remote sensing feedback to maintain its output
voltage constant, with no output impedance, a general-purpose DC source can be a nearly perfect voltage source. Here, unlike with a battery, its voltage does not decrease with load current. Moreover, feedback regulation is not instantaneous, which causes voltage drop and overshoot with the changes in loading and unloading. A significant transient voltage drop can activate a device’s low-battery-voltage shutdown. A regular DC source differs from a battery, but it can imitate it,
which helps get more reliable results during emulation. Make sure the power supply used has a programmable output resistance.
Extending battery life Using a battery emulator instead of a battery has several advantages for testing devices: • It creates a safer test environment: By using an emulator, designers don’t have to physically charge and discharge batteries, which becomes dangerous with cycling;
• It achieves repeatable results: Characteristics of an emulated battery do not vary from physical batteries, whose characteristics can fluctuate aſter charging and discharging. Tey can also vary between different batteries, even for the same model.
• It reduces test setup times: Designers can instantly simulate any state of charge (SoC) versus manually draining a battery to the desired level to speed test. A battery emulator operates through several steps. Te initial
one is to load a battery profile, the data from a graph of the battery voltage and internal resistance against the SoC, as shown in Figure 1. Designers can generate a battery profile using battery modelling soſtware, or get a profile from a battery provider; see Figure 2. Creating a profile with modelling soſtware will make it match
the current consumption for a particular device, which is more precise than a generic profile from a battery supplier. For instance, a generic profile is not helpful if the battery supplier makes it based on a steady current draw when the device under test has a variable
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