Battery Management System Introduction - Penelope Bise - June 2013

PENELOPE BISEBattery Management System an Introduction

210.04.2023 NEXT ENERGY

Content

•Motivation•Safe Operation Area•Battery Management System•BMS Key Functions •General Functions•Balancing•Performance•Conclusion

Motivation


● Batteries are key.

● Vital, the global market for storing power is forecast to explode

● Batteries face issues like safety and cost

● Lithium-ion batteries aboard two Boeing 787s jets failed in January, causing a fire on one and smoke on the other

● Li-ion batteries are fragile and a protection circuit is required to assure safety, even if they can provide super-high capacity.


Typical battery characteristics


Safe Operation Area for a Li-Ion Cell


Battery Management System (BMS)

BMS system has for objective:

• Protection and prevention of the system from damage

• Increase of battery life

• Maintenance of the battery system in accurate and reliable state

• BMS = Battery Doctor


BMS Key Functions

BMS key functions Balancing

Thermal management

Electrical management

Safety management

Data acquisition

Communication


BMS Functionality


BMS Key Functions


State of Charge (SOC)

The State of charge is the available capacity, it also called "Gas Gauge" or "Fuel Gauge" function

Of the various techniques for estimating SOC, two are:•The battery voltage translation•The battery current integration ("Coulomb Counting")


State of Charge

A major factors that can influence the SOC of a Lithium Batteries is the useable capacity of a cell, is not constant but varies significantly with temperature

The ratio of the currently available capacity to the maximum capacity can be expressed as SOC

Where i is the current, and n C is the maximum capacity that the battery can hold.


Balancing


Balancing


Balancing


Unbalanced battery pack


Balancing

Passive balancingRemoving the excedent of charge from a full charged cell using for that purpose a resistor in order to have a match between the cell of the lower cells in the charge reference.

Active balancingRemoving charge from higher energy cells and delivering it to lower energy cells, for that purpose element as capacitor are used for storing the energy.


Passive and active cell balancing methods


State of Health (SOH)

•Is a measure to analyze aging processes of the battery•Is used to evaluate the battery value degradation•Is an indicator of whether maintenance actions are needed

There are various methods to calculate the battery SOH using:•battery impedance, •battery capacity, •charge/discharge cycles •and calendar life

The aim is to predict the battery's healthy state


BMS Implementation

Source:http://www.mpoweruk.com/bms.htm

The Slaves – Each cell has a temperature sensor as well as connections to measure the voltage, all of which are connected to the slave which monitors the condition of the cell and implements the cell balancing


BMS Implementation

BMS distributed topology: daisy chained


Conclusion

BMS is a essential element for the battery to perform surveillance, control, balance and diagnostic in order to not just keep the cells secure state but to collect data that have the possibility evaluate how the battery behave with time.

10.04.2023 22NEXT ENERGY

References

[1] Davide A. (2010): Battery Management Systems for Large Lithium Ion Battery Packs; Artech House, ISBN 1608071049

[2] Speltino C. (2010): The Lithium-Ion Cell: Model State of Charge Estimation and Battery Management System; Presentation at the University of Sannio Benevento

[3] Lu l. et al. (2013) A review on the key issues for lithium-ion battery management in electric vehicles; Journal of Power Sources 226 (2013) 272e288

[4] Dai H. et al. (2012), A Hardware-in-the-Loop System for Development of Automotive Battery Management SystemMeasuring Technology and Mechatronics Automation in Electrical Engineering Lecture Notes in Electrical Engineering Volume 135, 2012, pp 27-36

[5] Balakrishnan P. et al. (2006): Safety mechanisms in lithium-ion batteries; Journal of Power Sources 155 401–414

[6] Chiu P. et al. (2005): B#: a Battery Emulator and Power Profiling Instrument; IEEE Design & Test of Computers March–April

[7] Nec-Tokin (2009): Characteristics of Li-Ion Batteries; www.nec-tokin.com

[8] Jossen A. et al. (2010) Reliable Battery Operation – A Challenge For the BMS; Journal of Power Sources


Thanks for your attention!


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Battery Management System Introduction - Penelope Bise - June 2013

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