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    Battery Management System, all you need to know


    As part of its efforts to reduce carbon emissions, the automobile sector is looking at alternate green energy fuel to power the vehicles and lithium-ion battery has found a wide acceptance.

    The performance of an electric vehicle in addition to the motor, a lot many factors also play a vital role: the cell voltage, battery health, safety measures, charging-discharging rates and many more taking to one common term, the Battery Management System (BMS). 

    Electric vehicles and the efficiency in their performing outputs is all based on the BMS, the system that ensures the complete tracking, monitoring and controlling of the functions performed by the battery for a reliable and safe operation. It therefore becomes a critical feature when it comes to EV safety. It helps with the real-time information which aid timely actions and hence contribute to improved performance of the EV while also ensuring the durability of the vehicle.  

    What is the need of BMS? 

    Time and again, the need for switching to electric modes of transport has been discussed and pondered over. There have been a lot of advancements as well in terms of power and energy of the lithium-ion batteries, widening the scope for the industry consequently. 

    This also brings into picture the most important aspect of safety. The many benefits of EVs yet the concern over the safety related issues is where things become tricky. This is why the EVs have a BMS, to ensure safety and the stability of the battery packs. 

    Technically, BMS is the system of purposely built circuit boards and processors that keeps check on the performance of the EV’s battery. Measuring the set parameters is crucial and thus ignoring or bypassing it can lead to thermal runaway which leads to fire in EVs. Breaching the limits in case of high voltage EV batteries is a clear indication that vehicles might catch fire, get oerheated or become useless.

    How Does the BMS Aid Battery Charging?

    A BMS system is designed and customised depending on the end-application that would be using the system, however, there a lot of common functionalities. 

    BMS monitoring becomes more important when it comes to charging control that is two stage task. Firstly, the constant current stage wherein the battery is charged through a constant current from the charger. Secondly, the constant voltage stage where even at very low current, the battery is supplied with constant voltage. 

    The EVs have a battery state of charge (SOC) indicator like the fuel indicators in all vehicles. The BMS aids in indicating the driver the actual charge status of the battery. Voltage and current measurements are based on applying the algorithms using the calculations of SOC. 

    Additionally, the BMS also is responsible for monitoring the state of health (SOH). The battery health that depletes over time can be determined and along with this the milege on each charge.

    Types of Battery Management Systems

    The BMS also has types ranging from simple to complex and can serve a good deal of variation in technologies to achieve the final goal of taking care of the EV battery. 

    Centralised BMS Architecture 

    This type has a centralised battery pack assembly, which is advantageous for some concepts, if not all. Being economical and compact as the same this, this BMS has a good economic value. 

    There lies a big disadvantage as well, being only one central BMS means a lot of clutter and multiple batteries are connected to the BMS directly. This makes the troubleshoot and maintenance all the more complicated when it comes to larger battery packs. 

    Modular BMS Topology

    This type is divided to several duplicate modules with dedicated wire bundles and connections to adjacently assigned portions of the battery stack. This duplicacy makes the troubleshooting and maintenance easier, unlike the centralised BMS architecture and extension to larger battery packs is quite a straighforward approach here. The only drawback is the slightly higher overall costs.

    Primary/Subordinate BMS

    This type comes with the salves more restricted to relaying measurements and the BMS is dedicated to computation and control along with the external communication. This type again is conceptually designed the same way as the modular BMS, costs may differ slightly. 

    The other functionaltionlities of BMS includes battery authentication that prevents third-party connections, real-time clock (RTC) which is used as a time stamp, memory for storage purposes, the voltage reference/regulator to power the peripheral circuitry around the BMS system and daisy chain circuitry to simplify the connection amongst stacked devices. 

    BMS is the core behind the smooth functioning of any EV and this is why considerations need to be well sought and battery requirements and battery-life goals should be determined in advance to work with the apt architecture, functional blocks, and related ICs. 

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