e-ISSN: 2582-5208

International Research Journal of Modernization in Engineering Technology and Science

( Peer-Reviewed, Open Access, Fully Refereed International Journal )
Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com

BATTERY MANAGEMENT SYSTEM FOR ELECTRIC VEHICLE

Sagar Sutar*1, Ramkrushna Shinde*2, Dhanashree Patil*3, Sayali Jamdade*4,
Rutuja Chougule*5, Prof. Sanjay Dhaygude*6, Rohan Doshi*7
*1.2.3.4.5Student, Department Of Electronics Engineering, Walchand Collage Of Engineering,
Sangli, Maharashtra, India.
*6Training & Placement Officer (TPO), Project Guide, Department Of Electronics Engineering,
Walchand Collage Of Engineering, Sangli, Maharashtra, India.
*7Senior Technical Lead, Mentor, FORVIA HELLA India Automotive, Pune, India.
DOI : https://www.doi.org/10.56726/IRJMETS36039
ABSTRACT
Battery Operation system / Battery management system (BMS) is one of the most important parts of any
electric vehicle which is used to cover and control the charging and discharging of rechargeable batteries.
Which ensures the safe operation of battery. It monitors the parameter determine soc & it provides necessary
service to ensure safe operation of battery. In order to maintain the state of the battery current, voltage and
ambient temperature, different monitoring techniques are used. For monitoring purpose various sensors are
used with microcontrollers this paper addresses state of charge, temperature monitoring & control, cell
balancing. By considering all these concepts future challenges and possible solutions can be obtained.
Keywords: SOC (State Of Charge), Temperature Control, BMS (Battery Management System) Etc.
I. INTRODUCTION

Fig 1. Block Diagram of BMS

Electric vehicles are the future of transportation. EVs are playing a crucial part because of its zero emigration of
dangerous feasts and use of effective energy. Electric vehicles are equipped by a large number of battery cells
which requires an effective BMS while they're furnishing necessary power.
Battery Management system (BMS) is the pivotal system in electric vehicle because batteries used in electric
vehicle should not be get overcharged or over discharged. If that happens, it leads to the damage of the battery,
rise in temperature, reducing the life span of the battery, and occasionally also to the persons using it. It's also
used to maximize the range of vehicle by duly using the quantum of energy stored in it.
Battery Management system is essential for following reasons:
1. Maintain the safety and the trustability of the battery.
2. Battery sate monitoring and evaluation.
3. To control the state of charge.
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International Research Journal of Modernization in Engineering Technology and Science
( Peer-Reviewed, Open Access, Fully Refereed International Journal )
Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com
4. For cell balancing and temperature controlling.
5. operation of regenerative energy.
II. METHODOLOGY
SOC (State of Charge):
The soc measurement of battery is an important parameter or feature of the battery capacity. it can’t be
measure directly. it can be only estimated through measurable variables such as current, voltage and
temperature. Various SOC estimation methods are there but Accurate soc (state of charge) estimation is one of
the main issues in BMS. an equivalent electric circuit has been used to describe the battery model.
State of charge is defined as the available quantum of battery as the chance of rated capacity of the battery.
State of charge gives a vital support to battery operation system to assess the state of the battery which helps
the battery to operate within the safe operating range by controlling charging and discharging. The battery
lifetime is also increased by this. State of charge can’t be estimated directly. It's calculated by using the equation

…………..(1)
Where I =current and
Cn= maximum capacity that the battery can hold
There are multiple methods to estimate the state of charge. Following are the list of state of charge estimation
system:
1. OCV SOC estimation system (Open Circuit Voltage)
2. Coulomb counting SOC estimation system
3. Kalman filtering SOC estimation system
Among all these different methods Kalman filtering system has been successful for the estimation of SOC for
EV’S.
Temperature Monitoring & Control:
During operations of battery because of chemical reactions it produces heat in batteries. as load varies there is
chances of temperature rise or drop, damage the chemical property of cells and it can lead to explosion in worst
cases.
The temperature monitoring and control is essential for safer and smooth operation of batteries. The higher
temperature of batteries can lead abnormal behavior like fire catch up and lower temperature can affect the
charging and discharging parameter (current or voltage) of battery, may it can also reduce the power handling
capability of batteries.
Cell Balancing:
In order to meet the requirements of energy storage rechargeable batteries are widely used in electric vehicle
and other areas also. in various applications because of low terminal voltage of individual battery cells, they all
are normally connected in series to create battery pack to reach required voltage level. however, the
imbalances between individual cells of a battery pack are a common phenomenon. a well- known imbalances is
SOC (State of charge) differences between all cells [4] This imbalance is caused by both intrinsic and extrinsic
difference among battery cell [5]
The soc differences between cells are because of energy consumption of each cell is different. A li-ion battery
pack is having safety issue if overcharging and undercharging occurs, at the time of discharging the cell with
lowest soc will reach the lower limit of safe operation voltage first thus the BMS has to turn of the operation.
Same things (similar situation) happen during charging of battery. the cell with highest soc will reach upper
limit of safe operation voltage first.
This overcharge and undercharge cause on SOH (state of health) of battery. In order to maintain a balanced
battery bank two methods are there: 1. Passive cell balancing 2. Active cell balancing

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International Research Journal of Modernization in Engineering Technology and Science
( Peer-Reviewed, Open Access, Fully Refereed International Journal )
Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com
III. MODELING AND ANALYSIS
State of Charge & Thermal management:

Fig 2. Block Diagram of Kalman Filter

The SOC is one of the most important information in a BMS; it is an inner state of each cell [6], which
cannot be measured directly during operation of the battery. Accordingly, estimation is the only way to
determine a value of SOC. SOC is mathematically defined as follows [7]:

…………..(2)
SOCbatt: The state of charge of the battery.
SOCinitial: The initial state of charge.
Ah: Battery capacity in A / H.
Ibatt: Battery current.
Under the assumption that all the parameters of the model are constant, we have linear equations structuring
our model; therefore, we can use a linear state observer such as Kalman filter algorithm. This observer
equations are given below and will be used for our next presented results. (Fig 4,5&6).
A. SOC estimation using Kalman filter:
The Kalman filter algorithm can be represented in four equations as follows:
Prediction of state space variables

…………..(3)
Prediction of the covariance matrix

…………..(4)
Update of the Kalman gain

…………..(5)
Estimation of the state variable and correction of th prediction

…………..(6)
Estimation of the estimation error

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Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com

…………..(7)

Fig 3. Circuit Diagram of SOC Estimation and Thermal management.

Fig 4. Difference between Real & Estimated SOC.

Fig 5. Charging

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Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com

Fig 6. Discharging
Cell Balancing:

Fig 7. Cell Balancing

Active cell balancing is a point set up in some battery Management systems (BMS) that helps to keep the voltage
of all the cells in a lithium- ion battery pack within safe situations. This is done by covering the voltage of each
cell and, when necessary, transferring energy from the advanced- voltage cells to the lower- voltage cells. By
keeping all the cells within a certain voltage range, it helps to help anyone cell from getting overcharged or
discharged, which can dock the overall lifetime of the battery pack.
There are numerous different ways that active cell balancing can be enforced, but utmost systems use some
form of MOSFETs (essence- oxide- semiconductor field- effect transistors) to control the inflow of current
between cells. When a cell’s voltage gets too high, the current is diverted down from that cell and into another
cell with a lower voltage. This process continues until all the cells in the battery pack are within the safe voltage
range. While active cell balancing can help to protract the life of a lithium- ion battery pack, it’s not reliable and
there are still some pitfalls associated with using this type of system. One implicit issue is that if one cell
becomes damaged or demoralized, it can beget problems for the rest of the cells in the pack. also, if the BMS

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International Research Journal of Modernization in Engineering Technology and Science
( Peer-Reviewed, Open Access, Fully Refereed International Journal )
Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com
itself fails, it could lead to disastrous failure of the entire battery pack. Active cell balancing is a point in battery
operation systems that helps to keep the cells in a lithium- ion battery pack within a safe operating range. This
is done by periodically covering the cell voltages and currents and conforming the charge and discharge rates
consequently. By doing this, active cell balancing can help to help unseasonable aging of the cells and extend the
overall life of the battery pack.

Fig 8. CB Flowchart

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Fig 9. Cell Balancing Circuit Diagram.

In This first SOC of cell1 and cell2 will be compared if SOC1 is greater than SOC2 then switch (s1) will turn ON
and energy will transfer from cell1 to cell2 through switch and inductor. If SOC2 >SOC1 then switch (s2) will
turn ON and energy will transfer from cell2 to cell1 through diode1. after that SOC of cell3 and cell4 will be
compared if SOC3 is greater than SOC4 then switch (s3) will turn ON and energy will transfer from cell3 to cell4
through switch & inductor. If SOC4 >SOC3 then switch (s4) will turn ON and energy will transfer from cell4 to
cell3 through diode3. Next SOC of cell1 and cell3 will be compared if SOC1 is greater than SOC3 then switch (s1)
& switch (s2) will turn ON and energy will transfer from cell1 to cell3 through switch and inductor. If SOC3
>SOC1 then switch (s3) will turn ON and energy will transfer from cell3 to cell1 through diode2 & diode1. Next
SOC of cell2 and cell4 will be compared if SOC2 is greater than SOC4 then switch (s2) & switch (s3) will turn ON
and energy will transfer from cell2 to cell4 through switch and inductor. If SOC4 >SOC2 then switch (s4) will
turn ON and energy will transfer from cell4 to cell2 through diode3 & diode2. Same process will follow for ‘n’
number of cells.

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Fig 10. Cell Balancing Output

IV. RESULTS AND DISCUSSION
The model of the complete soc estimation and temperature monitoring and control in fig. 3 has been developed
and tested with noisy signal. the fig.3 consists of two parts 1. Temperature control 2. SOC estimation using
Kalman filter. 1). When battery is in operation, the electrochemical processes which produces heat which
increase the battery temperature for that convective heat transfer is used to maintain temperature of battery. 2.
For soc estimation Kalman filter method is used this method is one of most accurate soc estimate method.
In fig4 the waveform indicates the difference between real soc and estimated soc which are approximately
equal (Green color signal indicates real soc & pink color signal indicate estimated soc). Fig10 shows the output
of cell balancing circuit the technique of cell balancing used in this paper is active cell Balancing. initial SOC of
each cell is different in fig10 and after some time the SOC of all cells are maintained at constant level.
V. CONCLUSION
In this way we are developing the model for battery management system in electric vehicle by controlling key
parameters like current, voltage, temperature, and SOC (State of Charge).
It is an important that the BMS should be well maintained with battery credibility & security. this paper mainly
focusses on the study of battery management system and enhance the power performances of electric vehicles.
Besides, the goal of reducing the greenhouse gas can greatly be achieved by using battery management system.
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International Research Journal of Modernization in Engineering Technology and Science
( Peer-Reviewed, Open Access, Fully Refereed International Journal )
Volume:05/Issue:04/April-2023 Impact Factor- 7.868 www.irjmets.com
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