The document discusses battery management systems (BMS) and their importance for lithium-ion batteries. A BMS monitors cells to ensure safety, increases battery life, and maintains the battery system in an accurate state. Key BMS functions include balancing cells, estimating state of charge, determining state of health, and protecting the battery from damage. The BMS helps keep individual cells in a secure state and collects data to evaluate battery performance over time.

1. PENELOPE BISE
Battery Management System
an Introduction

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

3. Motivation
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● 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.

4. Typical battery characteristics
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5. Safe Operation Area for a Li-Ion Cell
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6. Battery Management System (BMS)
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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

7. BMS Key Functions
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BMS key
functions
Balancing

8. BMS Functionality
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9. BMS Key Functions
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10. State of Charge (SOC)
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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")

11. State of Charge
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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.

12. Balancing
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13. Balancing
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14. Balancing
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15. Unbalanced battery pack
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16. Balancing
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Passive balancing
Removing 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 balancing
Removing charge from higher energy cells and delivering it to lower energy
cells, for that purpose element as capacitor are used for storing the energy.

17. Passive and active cell balancing methods
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18. State of Health (SOH)
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•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

19. BMS Implementation
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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

20. BMS Implementation
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BMS distributed topology:
daisy chained

21. Conclusion
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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.

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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
System
Measuring 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

23. Thanks for your attention!
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