COVER STORY A Guide to I
n the first part of this article which was published in the June 2023 issue of this magazine we covered some of the challenges involved in designing fast-charging battery systems. By implementing fuel gauge functionality in the battery pack, original equipment manufacturers (OEMs) can design smart fast chargers that increase system flexibility, minimise power dissipation, ensure safe charging/discharging, and improve the overall user experience. In this second part we will explore the implementation details of a fast-charging system with parallel batteries using evaluation kits and a Raspberry Pi board.
Evaluating 1S2P Architectures Evaluating a simple charging system and testing its functionality can typically be done with an evaluation kit. These kits include all the necessary hardware and software applications, as well as graphical user interface (GUI)-based tools and APIs, to configure charging systems.
However, complex systems that require multiple cells are correspondingly more complex to evaluate. Complex systems may have several devices that need to be characterised. Developers will need to write some software code to read the signals generated from different system parts, analyse them, and take action. Consider a two Li+ cells in a parallel battery fast charging system using the MAX17330. As described in the data sheet, the MAX17330 can be used to charge and control two Li+ cells simultaneously. This system requires two MAX17330 ICs each managing one Li+ cell, and a buck converter (such as the MAX20743) with the capability to change its output voltage on-the-fly.
A microcontroller is required to configure and manage battery charging as well as to handle communication between the two ICs. Because it is a commonly used platform for system testing, we chose a Raspberry Pi board using Python as the programming language. The Raspberry Pi manages communications over I2
Battery Fast Charging
Franco Contadini, Staff Engineer, and Alessandro Leonardi, Account Manager, Field Sales, both with Analog Devices
Figure 1. A 1S2P charging system evaluation architecture using Raspberry Pi.
debugging, including charge current, battery voltage, and battery state of charge (SOC). These values are stored in an Excel file to enable offline analysis.
Testing the 1S2P Architecture This section shows how the charger and fuel gauge (MAX17330) are tested. It also describes the real performance that can be expected from parallel charging. For the most flexibility
and control, the device is programmed by a microcontroller using I2
C.
Figure 1 shows the 1S2P system architecture and the connections that are needed to evaluate the charging of two cells in parallel. The Raspberry Pi controls the three EVKITs: one MAX20743EVKIT (buck converter) and two MAX17330EVKITs (charger + fuel gauge). Data is logged in an Excel file.
The GUI-based, MAX17330 EV Kit Software is
C and logs important system parameters useful for evaluation and 14 Figure 2. Configuring the MAX17330 for parallel charging. FEBRUARY 2024 | ELECTRONICS FOR ENGINEERS
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