Exploring Communication Methods in Battery Management Systems: Challenges and Solutions
Understanding the communication methods of a battery management system (BMS) is critical to its successful operation. The BMS is the brain of any battery-powered device or system and is responsible for managing and controlling its performance. It is essential to communicate with the BMS to ensure it operates correctly and to monitor its performance. This article will explore the various communication methods used in a BMS and their advantages and disadvantages.
The central controller of a BMS communicates internally with its hardware operating at a cell level or externally with high-level hardware such as laptops or an HMI. High-level external communication is simple and uses several methods. These methods include different types of serial communications, CAN bus communications, and different types of wireless communications. However, low voltage centralized BMSes do not have any internal communications.
Distributed or modular BMSes must use some low level internal cell-controller (modular architecture) or controller-controller (distributed architecture) communication. These types of communications are difficult, especially for high voltage systems. The problem is voltage shift between cells. The first cell ground signal may be hundreds of volts higher than the other cell ground signal. Apart from software protocols, there are two known ways of hardware communication for voltage shifting systems, optical-isolator, and wireless communication.
Optical-isolator is one of the hardware communication methods for voltage shifting systems. It is an electronic device that uses light to transfer signals between isolated circuits. It is advantageous as it prevents ground loops and eliminates potential differences between circuits. However, it is more expensive than other communication methods, and its data transfer rate is slower.
Wireless communication is another hardware communication method for voltage shifting systems. It is advantageous as it eliminates the need for physical wires, making it more reliable and less expensive. However, it requires more power to transmit signals, and it is more prone to interference and jamming.
Another restriction for internal communications is the maximum number of cells. For modular architecture, most hardware is limited to a maximum of 255 nodes. For high voltage systems, the seeking time of all cells is another restriction, limiting minimum bus speeds and losing some hardware options. Cost of modular systems is important, because it may be comparable to the cell price.
The combination of hardware and software restrictions results in a few options for internal communication. These options include isolated serial communications and wireless serial communications. Isolated serial communications use serial data transmission between nodes that are electrically isolated. It is an effective communication method, but it requires more components, making it more expensive. Wireless serial communication uses wireless data transmission between nodes. It is more cost-effective than isolated serial communication, but it is less reliable due to the susceptibility of the wireless signals to interference and jamming.
To bypass power limitations of existing USB cables due to heat from electrical current, communication protocols implemented in mobile phone chargers for negotiating an elevated voltage have been developed. The most widely used protocols are Qualcomm Quick Charge and MediaTek Pump Express. “VOOC” by Oppo (also branded as “Dash Charge” with “OnePlus”) increases the current instead of voltage with the aim of reducing heat produced in the device from internally converting an elevated voltage down to the battery’s terminal charging voltage. However, it makes it incompatible with existing USB cables and relies on special high-current USB cables with accordingly thicker copper wires. More recently, the USB Power Delivery standard aims for a universal negotiation protocol across devices of up to 240 watts.
In conclusion, communication is an essential component of any battery management system. The communication method used should be reliable, efficient, and cost-effective. When selecting a communication method, the cost, reliability, data transfer rate, and susceptibility to interference and jamming should be considered. The BMS must be able to communicate with the central controller and external hardware to ensure it operates correctly and to monitor its performance. The internal communication methods for distributed or modular BMSes are particularly challenging, especially for high voltage systems, due to voltage shift and seeking time limitations. Nonetheless, there are hardware communication options available, such as optical-isolator and wireless communication. However, these options come with their own set of advantages and disadvantages. Ultimately, the most appropriate communication method for a given BMS will depend on factors such as cost, reliability, and data transfer rate.
Furthermore, advances in mobile phone charging protocols have led to the development of communication protocols, such as Qualcomm Quick Charge, MediaTek Pump Express, and VOOC by Oppo. These protocols aim to bypass power limitations in existing USB cables due to heat from electrical current. The USB Power Delivery standard is another recent development, aiming for a universal negotiation protocol across devices of up to 240 watts.
Overall, communication is a critical component of a BMS, and the right communication method is crucial for its proper operation. While there are challenges in selecting a communication method, there are hardware and software communication options available, such as optical-isolator, wireless communication, and serial communications. However, it is important to weigh the advantages and disadvantages of each option and consider factors such as cost, reliability, and data transfer rate. By selecting the appropriate communication method, a BMS can operate effectively and ensure the efficient and reliable performance of the battery-powered device or system it controls.
