Project 1
QUESTION
AIM : Design a battery pack for a car roughly 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell.
OBJECTIVES :
- Design the battery pack configuration.
- Draw the BMS topology for this battery pack.
2.Draw the BMS topology for this battery pack
BMS topologies fall in three types:
Centralized:
- It is a single controller is connected to the battery cells through a multitude of wires
Distributed:
- It is a BMS board is installed at each cell with just a single communication cable between the battery and a controller
Modular:
- It is a few controllers each handling a certain number of cells with communication between the controllers
- Here we mainly used the Master Salve topology because This architecture comprises of the Master and Slave BMS units.
- so by this The slave unit monitors balances and controls a group of battery cells within the battery module.
- It communicates with the master unit through a communication interface.
- The Master unit is responsible for state estimation control of Power Distribution Unit PDU and external communication.
- The master-slave BMS is similar to a modular system in the sense that it uses multiple identical modules the slaves each measuring the voltage of a few cells.
- However the master is different from the modules and does not measure voltages.
- It only handles computation and communications.
Importance of BMS Architecture for EV Battery Systems
- Measurement Precision
- Connection Reliability
- Expansion Versatility
- Here The main function of Battery Management System BMS is to ensure that the battery is protected and any operation out of its safety limit is prevented.
- It monitors the battery pack's state of charge SOC along with the state of health SOH
Battery management system (BMS) is technology dedicated to the oversight of a battery pack, which is an assembly of battery cells, electrically organized in a row x column matrix configuration to enable delivery of targeted range of voltage and current for a duration of time against expected load scenarios. The oversight that a BMS provides usually includes:
- Monitoring the battery
- Providing battery protection
- Estimating the battery’s operational state
- Continually optimizing battery performance
- Reporting operational status to external devices
Here, the term “battery” implies the entire pack; however, the monitoring and control functions are specifically applied to individual cells, or groups of cells called modules in the overall battery pack assembly. Lithium-ion rechargeable cells have the highest energy density and are the standard choice for battery packs for many consumer products, from laptops to electric vehicles.
While they perform superbly, they can be rather unforgiving if operated outside a generally tight safe operating area (SOA), with outcomes ranging from compromising the battery performance to outright dangerous consequences. The BMS certainly has a challenging job description, and its overall complexity and oversight outreach may span many disciplines such as electrical, digital, control, thermal, and hydraulic.
Battery management systems do not have a fixed or unique set of criteria that must be adopted.
The technology design scope and implemented features generally correlate with:
- The costs, complexity, and size of the battery pack
- Application of the battery and any safety, lifespan, and warranty concerns
- Certification requirements from various government regulations where costs and penalties are paramount if inadequate functional safety measures are in place
There are many BMS design features, with battery pack protection management and capacity management being two essential features. We’ll discuss how these two features work here. Battery pack protection management has two key arenas: electrical protection, which implies not allowing the battery to be damaged via usage outside its SOA, and thermal protection, which involves passive and/or active temperature control to maintain or bring the pack into its SOA.
Electrical Management Protection: Current
Monitoring battery pack current and cell or module voltages is the road to electrical protection. The electrical SOA of any battery cell is bound by current and voltage. Figure 1 illustrates a typical lithium-ion cell SOA, and a well-designed BMS will protect the pack by preventing operation outside the manufacturer’s cell ratings. In many cases, further derating may be applied to reside within the SOA safe zone in the interest of promoting further battery lifespan.
CONCLUSION:
We have succesfully designed the batter pack configuration and we drawn a BMS topology for the battery pack