Project 1 Mechanical design of battery pack
Aim :-
Battery Pack Capacity :- 18kWh
Cell :- ANR26650M1-B
Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.
Introduction :-
As we know that the electric vehicle market is gradually increasing, with the growth of an electric vehicle the growth and interest in Lithium-ion cell are also increasing. The energy source for an electric vehicle is stored in cyclindrical cells.
Lithiukm-ions cells are capable of delivering very high power, Lithium-ion cells are used in aerospace automotive electric vehicle mobile device medical device and other electronic devices which is based on these cells. The battery pack is installed in lower-floor of the electric vehicle so that weight may distribute equally and also the centre of gravity also maintain properly.
The high voltage battery pack is one of the most important components of any electric vehicle. The traction battery of electric vehicle must achieve the followingthing.
a. Provide maximum traction motor torque
b. Vehicle range in sense of kilometre
c. To achieve the proper life cycle of battery
The battery pack of an electric vehicle generally having a series of paralle combination large battery pack have multiple cell modules in which many numbers of cell kept together to build a large battery pack.
Mechanical Design of Battery Pack :-
a. Mechanical vibration should decrease
b. Controlling on high impact force
c. Better thermal runway for cooling
d. Serviceability and recyclability
Safety and reliability are two major thing for large battery pack while mechanical designing of large battery pack we should follow some technical criteria so that the battery may not fail.
For the designing of 18kWh battery pack here i use a base model of ANR26650M1B Lithium-ion cell. ANR26650M1B cell is consist of lithium iron phosphate chemistry and it is best for use in a wide range of temperature and conditions. The ANR26650M1B Lithium ion cell may achieve the following features.
a. Stable chemistry
b. Faster charging
c. Consistent output
d. Excellent cycle life
e. Superior cost performance
Technical Specification ANR26650M1B
Dimension :-
Applications :-
1. Energy storage
2. Uniterruptible power supplies
3. Communication technologies
4. Aerospace
5. Electrified mobility devices
6. Industrial equipment
7. Medical devices
8. Toys
Calculation as per assumptions : 18kWh Battery Pack
The mathematical calculation for designing an 18kWh battery pack, basically 18kWh is energy require to achieve the vehicle its proper range, it is depending upon the voltage parameter and ampere-hout or capacity.
Here i used to design a high voltage battery pack for an electric vehicle to achieve its range up to 250km. For this calculation i assumed 145.2 V nominal votlage for series connection.
General require3d value depending upon a singel cell ;
a. Diameter = `phi`25.96/26 mm
0.026 m
b. Length = 15/65 mm
0.065 m
c. Mass = 76 g
0.076kg
d. Single-cell Voltage = 3.3 V
e. Capcity = 6 Ah
f. Max COntinuous charge current (C-rate) = 10 A
e. Max pulse cahrge current (C-rate) = 20A
Mathematically Battery Calculation :-
Single Cell Calculation ;
= pi2h
= pi x o.o13^2 x 0.065
= 3.45104 x 10-5
= 3.14(0.026)^2*0.065
= 0.03451 m^3
Basically the value of the volume of the cell is used to find out the volume of the battery pack.
1. Single Cell Energy (Wh)
= Cell capacity (Ah) x Cell voltage (V0
= 2.6 x 3.3
= 8.58 Wh
The value of a single cell is used to calculate the total energy of the battery pack.
2.Single Cell Energy Density
Volumetric energy (Wh/M^3) = single cell energy / volume pf each cell
= 8.58 Wh / 0.03451 m^3
= 248.62 Wh/m^3
Gravimetric energy (Wh/kg) = single cell energy / single cell mass
= 8.58 Wh/0.076 kg
= 112.89 Wh/kg
Calculation of high voltage battery pack :-
For design and calculation of battery pack here i assume a vehicle to achieve 250km in 18kWh battery pack. Also. i assume 145.2 nominal voltage for series connection.
Vehicle Range = 250 KM
Battery Pack Capacity = 18.121 kWh 0r 18120.96 Wh
We will calculate per km average energy = 18120.6/250
=72.483 Wh/km
Battery pack total energy = Average energy x km
= 72.483 x 250
= 181,120.96 Wh
Nominal Voltage for series connection = 145.2V basically depends upon the motor power we can decide the value according to the motro.
No. of cells connected in series = Nominal voltage series connection / Nominal votlage of a single cell
= 145.2 V/3.3 V
=44
44 cells will be connected in a series connection to provide a proper voltage.
Energy for battery pack (Wh) = No. of cells connected in series x single-cell energy
= 44 x 8.58 Wh
=377.52 Wh
No. of cell connected in paralle = Battery pack total energy / Energy for battery pack
= 18120.96 / 377.52
=48
48 cells will be connected in paralle to provdie proper capacity power.
Battery pack total energy = No. of cells connected in paralle x Energy for battery pack
=48 x 2.6 Ah
= 124.8 Ah
The value of battery pack capacity is used for the total power required by the vehicle
Total No. of cells for battery pack = No. of cells connected in parallel x No. of cells connected in series
= 48 x 44
= 2112
2112 cells will be used to make complete battery pack.
Mass of battery pack = T. no. of cells of battery pack x Mass of single cell
= 2112 x 0.076 kg
= 160.512 kg
It is the total weight of cells connected in parallel or series
Total volume of the battery pack = T. no. of cells battery pack x volume of single cell
= 2112 x 0.0345
= 72.89 m^3
This is the volume of 2112 cells which are used in the battery pack system
cell peak current (A) = Crate(Max pulse charge current) x single cell capacity
= 20 x 2.6
= 52A
Battery pack peak current(A) = cell peak current x no. of cells connected in parallel
= 52 x 48
= 2496A
it is used for the operation of the battery pack by this way a vehicle will decide how much power is required to move,
Battery pack peak power (W) = Battery pack peak current x Voltage of series connection
= 2496 A x 145.2
=362419.2 W
Cell continuous current (A) = Crate(Max continuous charge current) x single cell capacity
= 10 x 2.6
=26 A
Battery pack continuous current(A) = cell contiuous current x no. of cells connectd in parallel
= 26 x 48
=1248 A
This is the power which is supply continue to the whole battery pack system.
Battery pack continuous power = Battery pack continuous current x voltage of series connection
= 1248 x 145.2
= 18120.96 kWh
above calculation is to find the total number of cell for a battery pack for electric vehicle also the battery pack weight current capacity and voltage. For design purpose and easy for installation here i configure this large battery pack into a small pack and consists 3 2 cells into 66 pack and every single pack will have 8S/4P.
Cad Modelling of Battery Pack by using CREO 7.0
for whole battery pack design i have used CREO 7.0
a.Cell Design and Assembly of Battery Pack
Single-cell dimension
- Diameter 26 +/- 0.5 mm
- Length 65 +/- 0.5 mm
A cell basically consisting of anode, cathode separator positive cap negative cap and gasket.
Arrangement and assembly of 8S/4P
The deatil technical specification of the single pack follow as;
- Package; 8S/4P
- Capacity; 4Ah
- Voltage; 26.4 V
- Weight; 2.432 kg
- of cells; 32
- Power; 274.56 Wh
Assembly of the battery pack with 44S/48P
single pack : 32 cells with 8S/4P
32 cells x 66 pack = 2112 cells
Then,
2112 cells with have 44S/48P
I arrange the pack such that it will build a proper battery pack.
The detail technical of 2112 battery pack follow as,
- Package; 44S/48P
- Capacity; 8Ah
- Voltage; 145.2 V
- Weight; 160.512 kg
- of cells; 2112
- Power; 18120.96
Here i also configure battery pack into electric vehicle lower floor panel case, a simple layout of the battery pack in electic vehicle shown.
The main function of a battery holder is to keep cells fixed place safely and securely also it is used to keep cells in a proper arrangement so that there will be decrease in mechanical vibration and have a better thermal runaway between the cell gaps. most of the cell holder is made up of polypropylene or nylon bodies rated for 80-100 C.
A dimension shown,
Basically pack cover is made up of aluminium and the reason behind to keep battery pack for lightweight. The casing/cover thickness is 0.5 mm and the design is shown.
A bottom cover is shown to cover below the bottom battery holder.
Basically the lower case is a part which fitted in an electric vehicle for the assembly and it has top cover and bottome cover battery pack form dust and environmental pollution.
The design of the lower case shown,
A positive and negative clip is used to connect the battery end cap, design is shown,
Cyclindrical cell have imporved thermal management efficiency because of compact shape but have low packaging efficiency because of their round cross section, here use a positive and negative tab to connect multi cells.
The suitable of joinin methods to build battery packs using cylindrical shown,
Results :-
Battery Calculation :-
Single cell calculation:-
Volume of single cell = 0.03451 m^3
Single cell Energy = 8.58 Wh
Single cell energy density ;
volumetric energy = 248.62 Wh/m^3
Gravimetric energy = 112.89 Wh/kg
Calculation of high voltage battery pack fo 18 kWh :-
Average energy = 72.483 Wh/km
Nominal voltage for series connection = 145.2 V
No. of cells connected in series = 44
Energy for battery pack = 377.52 wh
No. of cells connected in parallel = 48
Battery pack capacity = 124.8 Ah
T. no. of cells for battery pack = 2112
Mass of battery pack = 160.512 kg
Total volume of battery pack = 72.89 m^3
Cell peak current = 52 A
Battery pack peak current = 2496 A
Battery pack peak power = 362.42 kw
Cell continuous current = 26 A
Battery pack continuous current = 1248 A
Conclusion :-
As from the single-cell technical data here i have designed battery pack for the electric vehicle which is having total energy of 18.12kWh. The total no. of cells are 2112 which are in the configuration of 44S/48P also the nominal voltage from the 44 series connection of battery gives 145.2 and the capaity power we get from the arrangement of 48 parallel cells is 123.8Ah.
All design is used to achieve a 250km range by the vehicle which is an aumption to calculate the battery pack. Here i will increase but at that time the distance will not achieved by the vehicle that's why here i use 44S/48P cell configuration for the battery pack.
Also, the whole battery pack is subdivided into 66 pack in which each block has 32 cells and this configuration is prepared to set up 44S/48P cell configuration.
Also i used 2.6Ah as single-cell capacity instead of 2.5Ah if we use 2.5Ah then the battery pack configuration will be 44S/50P.
The detail parameter of single, 32 cell and 2112 cells are shown,
A battery discharge characteristic is also calculated based on single-cell configuration.
a. Nominal voltage = 3.3 V
b. Capacity = 2.6 Ah
So the total no. of cells used for the complete battery pack of 18kWh is 2112 with 44S/48P configuration.
Single cell configuration :-
Package - 1S/1P
Capacity - 2.6 Ah
Voltage - 3.3 V
Weight - 76 Gram
Power - 8.58 Wh
32 Cells Configuration :-
Package - 8S/4P
Capacity - 10.4 Ah
Voltage - 26.4 V
Weight - 2432 Kg
Power - 274.56
2112 Cells Configuration :-
Package - 44S/48P
Capacity - 124.8 Ah
Voltage - 145.2 V
Weight - 160.521 Kg
Power - 18.121 kWh