AUTOMATION & ROBOTICS C
hoosing an appropriate battery pack and its accompanying battery management system (BMS) is a critical decision in designing an autonomous mobile robot (AMR) as shown in Figure 1. In tightly integrated settings
like factories and warehouses, where every second of operation matters, ensuring the safe and reliable functioning of all components is of utmost importance.
BMS solutions can provide accurate measurements on the charging and discharging of the batteries, which maximises the usable capacity. Additionally, the precise measurements allow for an exact calculation of the state of charge (SoC) and depth of discharge (DoD), which are essential mobile robots. Equally important are the safety aspects of such systems and it becomes crucial to consider BMS technologies that provide both overcharge protection and overcurrent detection while selecting systems for these applications.
UNLOCKING EFFICIENCY: HOW ADI BATTERY MANAGEMENT SOLUTIONS EMPOWER SAFER, SMARTER MOBILE ROBOTS
By Rafael Marengo, system applications engineer, Analog Devices Figure 1. An AMR diagram.
WHAT ARE BATTERY MANAGEMENT SYSTEMS?
A BMS is an electronic system that can be used to closely monitor various parameters of a battery pack and/or its individual cells. It is critical for achieving the maximum usable capacity of the batteries while ensuring safe can not only optimise the usable capacity of the battery in a safe manner but also provide the engineers with valuable parameters such as the cell voltage, SoC, DoD, state of health (SoH), temperature and current, all of which can be used to get the best performance out of a system.
What are SoC, DoD and SoH and why are they important for automated guided vehicles (AGVs) and AMRs?
SoC, DoD, and SoH are a few of the common parameters used in BMS to determine if the system is healthy, early fault detection, cell aging and the remaining time of operation. SoC stands for state of charge and can be relation to its total capacity. SoC is usually expressed as a percentage where 0 percent = empty and 100 percent = full.
maximum capacity (Cmax) of the battery that can be released relative to its rated capacity (Cmax).
DoD or depth of discharge is the opposite percentage of the battery that has been discharged (Creleased) relative to its rated capacity (Crated).
HOW ARE THOSE RELEVANT FOR AN AMR SOLUTION?
The SoC of a battery varies according to the battery architecture, nonetheless, it is necessary to have a precise system to measure the state of a battery. Two main types of commonly used batteries are Li-Ion and lead acid batteries. Each has its pros and cons, with various subcategories. In general, Li-Ion batteries are considered a better choice for robots because they offer: • More energy density, which could be in the order of 8 to 10 times the energy density of a lead acid battery.
“The precision of battery management significantly enhances the efficiency of batteries by precisely measuring the cells, allowing for more accurate control and estimation of the SoC across various battery chemistries.”
• Li-Ion batteries are lighter than lead acid batteries of the same capacity.
• Charging a lead acid battery takes longer than charging a Li-Ion battery.
• Li-Ion batteries offer an extended life number of charge cycles.
However, these advantages come with a higher cost and pose certain challenges that need to be addressed to fully realise their
To better explain this in a real-life application, it is possible to analyse the plot in Figure 2, which compares the DoD of a lead acid battery and a Li-Ion battery. It can be observed that the pack voltage varies minimally for a Li-Ion battery while going from 0 percent DoD to 80 percent DoD. 80 percent DoD is usually the lower limit for Li-Ion batteries and anything below that can be considered a dangerous level. However, because the pack voltage on a Li-Ion battery only shifts minimally for the usable range, even a minor measurement error could lead to a substantial decrease in performance.
38 APRIL 2025 | FACTORY&HANDLINGSOLUTIONS
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