Project 1

PROJECT 1

1. Design a battery pack for a car roughly 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell.

a. Design the battery pack configuration.

b. Draw the BMS topology for this battery pack.

Aim of the project

To design a battery pack for a car with 150Kw capacity and with 120V nominal voltage. Each cell specifications are 3500 mAh and 3.6V is the cell nominal voltage which is of NMC chemistry cell.

Calculations of Requirements

The battery pack for a car designing parameters follows

=> Total capacity of the battery pack = 150Kw = 150KWh

=> Total nominal voltage of the battery pack = 120V

Each cell parameter are as follows

=> Cell chemistry type = NMC type battery

=> Cell capacity = 3500mAh = 3.5Ah

=> Cell nominal voltage = 3.6V

Calculations of designing the battery pack

=> Required battery pack capacity(Ah) = (KWh x 1000)/(Voltage of battery pack)

=> Required battery pack capacity(Ah) = (150 x 1000)/(120) = 1250Ah

so the following parameters of the battery pack are concluded

• Total capacity of the battery pack = 150KWh
• Total nominal voltage of the battery pack = 120V
• Required battery pack capacity(Ah) = 1250Ah

Designing the battery pack for a car

Series connected cells:

Number of cells required to connect in series = Voltage required by the battery pack / NOminal voltage of the cell

Number of cells required to connect in series = 120v/3.6v = 33.33 cells = 33 cells

No. of cells in series connection = 33 cells

Parallel connected cells:

Number of cells required to connect in parallel = Capacity required by the battery pack/Cell capacity

Number of cells required to connect in parallel = 1250Ah/3.5Ah = 357.14 cells = 357 cells

No. of cells in parallel connection = 357 cells

Observations

• So we had observed that, while calculating the number of cells in series and parallel, the required cells obtained are in decimal values but the cell's quantity cannot be taken in decimals.
• So The cell considered are of approx values and they are again calculated as follows
• If the No. of cells in series connection are taken as 34 cells, we'll have
• 34cells x 3.6v = 122.4V is the output from the battery pack and which is exceeds the required voltage i.e 120v, so we had considered only 33cells which gives us 119V which is almost to 120v
• If the No. of cells in parallel connection are 358 cells we'll get 1253Ah which can be considered and as well as 357 cells which gives 1249.5Ah can also be considered while taking battery capacity

Conclusion

=> No. of cells in series connection = 33 cells = 120v

=> No. of cells in parallel connection = 357 cells = 1249.5Ah

b. Draw the BMS topology for this battery pack

Introduction about BMS:

Battery management system (BMS) is used to Monitoring battery pack current and cell or module voltages is the road to electrical protectionBMS Topology used in this battery pack is Master and Slave BMS Topologi. Because the total battery pack is made of sub battery packs so controlling and manufacturing will be easy. It consisting of input sensors of volatge,current and temperature. The voltage sensor analog signal is converted to digital signal by AFE, the current sennsor analog signal is converted to digital signal by the MCU or we can connect the ADC converter between the Current sensor and MCU, the temperature sensor analog signal is converted to digital signal by the MCU or we can connect the ADC converter between the Temperature sensor and MCU.

fig(a) BMS with each cell connections

What is 3S2P battery pack configuration

The 3S2P battery pack configuration means

==> 3S2P = 3 cells in series connection and 2 cells in parallel connection

The total Number of the batteries required to design a battery pack should be designed in case like follows

==> Total Number of the batteries required = Cells in series x Cells in parallel

==> Total Number of the batteries required = 3 x 2 = 6 cells

So that the 3S2P battery pack is likewise designed. There must be 2 rows which consists of 3 in each row. The top row and bottom rows must be connected in series with each other and at last the both rows must be connected in parrallel with each other, to make a 3S2P battery pack configuration.

So this a example configuration for identifying the battery pack.

BMS topology for 33S357P configuration

The above problem has identified as 33S357P configuration. So replicating it here I had designed a BMS for that type of battery pack below. SInce the BMS Supports the maximum 18 cells in series so we need to divide the 33 series cells to 18 cells series sub battery pack which leads to 2 series sub connections one with 18 and another with 15.

I made 59 cells in parallel for each sub pack which leads to 6 parallel connections and other 2 cells for other subpack to meet the requirement of 33S357P type.

Total result in 2 sub battery packs in sereis one with 18 cells in series and another with 15 cells in series and 8 sub battery pack in parallel each with 59 cells in parallel and other 2 cells for other subpack to meet the requirment 33S357P type

Here we are considering the "Master and slave topology for BMS configuration". as shown below. This "Master and slave topology for BMS configuration" which has number of slave controllers are 16 and a Master controller which can handle 16 slaves as such.

Conclusion

This "Master and slave topology for BMS configuration" used. Total result in 2 sub battery packs in sereis one with 18 cells in series and another with 15 cells in series and 8 sub battery pack in parallel each with 59 cells in parallel and other 2 cells for other subpack to meet the requirment 33S357P type.

2. Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.

-------- DESIGN OF BATTERY PACK--------

Introduction of batteries

A battery is component that stores electrical energy in the form of chemicals and by means of electrochemical reaction. The battery converts the stored chemical energy into direct current (DC) electric energy. In simple, the electrochemical unit that is the source of electrical energy produced by conversion of chemical energy.

The electrochemical cells and batteries are classified into two types:

• Primary (non-rechargeable):

A Primary Battery is one of the simple and convenient sources of power for several portable electronic and electrical devices like lights, cameras, watches, etc. As they cannot be recharged electrically.

They are used for use and throw purposes only.

• Secondary (rechargeable):

A Secondary Battery is also called as 'Rechargeable Battery' as they can be electrically recharged after discharge. The chemical status of the electrochemical cells can be “recharged” to their original status.

This type of batteries are employed in trimmers, rechargable lamps, Electric vehicles. etc.

Type of batteries avaliable

There are most types based on their performance, requirements, size, and shape and their design, chemical type, etc. So here we gonna discuss about the types of chemical type of the battery. so in the market there are few types avaliable based on the chemical type used in it. The few of them are listed below.

• Lithuim-ion batteries:

Lithium ion batteries are the newest of the few types. These Li-ion batteries are the most expensive also and These batteries are ideal for portability as well. These Lithium ion batteries also recharges very quickly usually in 1-3 hours only which creates a major advantage of them compartively.

• Alkaline batteries:

Alkaline batteries are the oldest available batteries in the market and they were invented by Thomas edison and other simultaneously. They offers consistent performance from start to finish. These alkaline batteries are single use and must be disposable batteries. They are single use purposes and they are for use and throw cases only and cannot be rechargeable. Alkaline batteries are the cheapest.

• lead acid batteries:

The lead–acid battery is a type of rechargeable battery first invented in 1859 and lead–acid batteries have relatively low energy density. They are inexpensive comparetively. They have wide variety of applications like UPS systems, ignition power sources for automobiles, along with large, grid-scale power systems as well.

• Nickel metal hydride batteries:

NiMH batteries were one of the late invented battery. these are rechargeable. NiMH batteries are more expensive than alkalines battery. NiMH batteries also take long time to charge. NiMh batteries gets about 500 charges before reaching end-of-life. Their performance degrades with discharge time.

What is 3S2P battery pack configuration

The 3S2P battery pack configuration means

==> 3S2P = 3 cells in series connection and 2 cells in parallel connection

The total Number of the batteries required to design a battery pack should be designed in case like follows

==> Total Number of the batteries required = Cells in series x Cells in parallel

==> Total Number of the batteries required = 3 x 2 = 6 cells

So that the 3S2P battery pack is likewise designed. There must be 2 rows which consists of 3 in each row. The top row and bottom rows must be connected in series with each other and at last the both rows must be connected in parrallel with each other, to make a 3S2P battery pack configuration.

Design of the 3S2P battery pack

Here I had choosen a battery with the following parameters.

The battery is a "Lithuim-ion battery" used and it has

• Nominal voltage of the cell(v) = 7.2V
• Fully charged voltage of the cell(V) = 8.3807V
• Rated capacity of the cell(Ah) = 5.4Ah

We had employed 6 cells to design a battery pack so the calculation is as follows

• Nominal voltage of the battery pack(V) = 7.2V x 3 cells = 21.6Volts
• Fully charged voltage of the battery pack(V) = 8.3807V x 3 cells = 25.24volts
• Nominal capacity of the battery pack(Ah) = 5.4Ah x 2 = 10.8Ah

Battery(Cell) parameters:

Design of the 3S2P battery pack in SIMULINK

Outputs of SoC, Current, Voltage, battery pack voltage:

Observations

• So the battery pack voltage is observed as the '25.24v'. This is the voltage which is the fully charged voltage or the maximum voltage of the battery pack which is measured by the voltmeter.
• Nominal voltage of the battery pack(V) = 7.2V x 3 cells = 21.6Volts
• Fully charged voltage of the battery pack(V) = 8.3807V x 3 cells = 25.24volts
• Nominal capacity of the battery pack(Ah) = 5.4Ah x 2 = 10.8Ah
• These are the measurements and observation from the battery design of 3S2P configuration.

Conclusion

• '25.24volts' is the Fully charged voltage of the battery pack
• '21.6Volts' is the Nominal voltage of the battery pack which is the pratical voltage of the pack which must be considered while application
• The battery pack consists of 6 cells which are connected in series and parallel combinations. 3 are in rows(series connection)and those 2 rows are thus conncected in paralled to make a battery pack