Project 1 Mechanical design of battery pack
Attempted
Project:1
Mechanical design of battery pack
AIM:
Prepare a detailed battery pack of Cell: ANR26650M1-B, drawing along with its enclosure, and Battery pack capacity is 18kWh. State your assumptions.
ABSTRACT:
In this project, we are going to calculate the all parameters which are required for the build EV battery pack. We are going to use the Cell: ANR26650M1-B for our battery pack. In parameters, we will consider all electrical aspects like temperature, Depth of discharge, Operation current, Energy density, Work cycles, Battery capacity, State of Charge (SOC), State of Health (SOH), Ampere-hour (Ah) Capacity. We also calculate all geometrical considerations like size, weight, volume, area, etc. In the end, we consider some enclosures model for our battery pack.
OBJECTIVE:
1) Collecting the data of Cell: ANR26650M1-B from Nano phosphate High Power Lithium Ion Cell PDF.
2) Calculating all Electrical parameters for 18 kWh Battery Pack.
3) Calculating all Physical dimensions for Battery Pack.
4) Consider perfect enclosure for dimensions that we calculated for the Battery Pack.
METHODOLOGY:
1) To build the Battery pack for any Electric Vehicle, we have to calculate the first proportion of power then motor power, and depend on that we will model the battery pack so we know how much power we required which is 18kWh.
2) For the 18kWh battery Pack we have to calculate how many cells are parallel and how many cells are in series.
3) After calculation of series and parallel combination we have to calculate the proper Geometry and topology consideration for assembling batteries.
4) After Assembly we need to find a proper enclosure for the battery pack for thermal consideration and other physical damages.
THEORY:
The high voltage battery is one of the most important components of a battery electric vehicle (BEV). The battery parameters have a significant influence on other components and attributes of the vehicle, like:
- maximum traction motor torque
- maximum regeneration brake torque
- vehicle range
- vehicle total weight
- vehicle price
Pretty much all major aspects of a pure electric vehicle (EV) depend on the parameters of the high voltage battery.
For our electric vehicle battery design we are going to start from 4 core input parameters:
- chemistry
- voltage
- average energy consumption of the vehicle on a driving cycle
- vehicle range
A battery consists of one or more electrochemical cells (battery cells) which are converting chemical energy into electrical energy (during discharging) and electrical energy into chemical energy (during charging). The type of elements contained within a battery and the chemical reactions during discharging-charging events define the chemistry of a battery.
A battery cell consists of five major components: electrodes – anode and cathode, separators, terminals, electrolytes, and a case or enclosure. For automotive applications, there are different types of cells used Individual battery cells are grouped into a single mechanical and electrical unit called a battery module. The modules are electrically connected to form a battery pack.
ANR26650M1-B Specifications
Nominal Ratings
Voltage: 3.3 Volts
Capacity: 2.5 Ah
Energy: 8.25 Wh
Specific Power: 2600 W/kg
Impedance (1KHz AC Typical) 6 mΩ
Cycle Life at 1C/1C, 100% DOD: > 4000 cycles
Cell Type: 26650 Lithium Ion Power Cylindrical Cell
Discharging
Max Continuous Discharge: 50 A
Max Pulse Discharge Current >50% SOC (10s): 120 A
Minimum Voltage: 2 Volts
Temperature: -30ºC to 55ºC
Charging
Recommended Standard Charge: 2.5 Amps
Max Charge Rate: 10 Amps
Max Pulse Charge Current <50% SOC (10s): 25 A
Float Voltage: 3.45 Volts
Recommended charge V & Cut-off Current: 3.6 Volts, taper to 125mA
Temperature
(reduce charging current to 250mA when under 0ºC): 0ºC to 55ºC
Mechanical
Diameter: Ø25.96 +/- 0.5 mm (1.0")
Length: 65.15 +/- 0.5 mm (2.6")
Mass: 76 g
Calculation as per assumptions: 18kWh Battery Pack
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 (V) parameter and ampere-hour or capacity (Ah).
Here we design a high voltage battery pack for an electric vehicle to achieve its range up to 220 km. For this calculation, I assumed 145.2 V a nominal voltage for series connection.
Basically, the value of the volume of the cell is used to find out the total volume of the battery pack.
Single Cell Energy (Wh)
= Cell Capacity (Ah) x Cell Voltage (V)
= 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.
-Single Cell Energy Density
Volumetric energy (Wh/m^3) = Single Cell Energy / Volume of 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 250 km in 18 kWh battery pack. Also, I assume 145.2 nominal voltage for series connection.
So,
Vehicle Range = 250 KM (assumed)
Battery Pack capacity = 18.121 kWh or 18120.96 Wh (For better and accurate calculation here I change kWh)
Now,
We will calculate per km average energy = 18120.96 / 250
= 72.483 Wh/km
Therefore
Battery Pack total energy = Average energy x km
= 72.483 x 250
= 18120.96 Wh or 18.120 kwh
Let’s assume Nominal voltage for series connection = 145.2 V, Basically, this depends upon the motor power We can decide the value according to the motor.
Number of cells connected in series
= Nominal voltage of series connection / Nominal voltage 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
Number of cells connected in parallel
= Battery pack total energy (wh) / Energy for battery pack (wh)
=18120.96/377.52
= 48
48 cells will be connected in parallel to provide a proper capacity power.
Battery pack total energy (wh)
= No. of cells connected in parallel x Energy for battery pack (wh)
= 48 x 377.52
= 18120.96 wh or 18.120 kWh
Battery pack capacity
= No. of cells connected in parallel x Single cell capacity (Ah)
= 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 number of cells for battery pack
= No. of cells connected in parallel x No. of cells connected in series
=48x44
= 2112cells
2112 Cells will be used to make a complete battery pack.
Mass of battery pack
= Total no. of cells for batter pack x Mass of single cell
= 2112 x 0.076 kg
= 160.512 kg
it is the total weight of cells connected in parallel and series.
Total volume of the battery pack
= Total no. of cells for batter 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)
= C rate (Max Pulse Charge Current) x Single cell capacity
= 20 x 2.6
= 52 A
Battery pack peak current (A)
= Cell peak current x No. of cells connected in parallel
=52X48
= 2496 A
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
= 3624192 or 362.42 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 continuous current x No. of cells connected 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 (W)
= Battery pack continuous current x Voltage of series connection
=1248 x145.2
= 18120.96 or 18.120 Kwh
detailed battery pack drawing along with its enclosure.
BATTERY HOLDER SPACER For CELL CYLINDRICAL LI-ION
Nickel Strips
Nickel strip is generally used in battery building. Its due to its efficiency of usage in spot welding and soldering as well its high corrosion resistance over time. It has good properties and excellent resistance to many corrosive environments. The pure nickel will never get rust after it applied to battery packs. It won’t affect the current transfer between batteries.
Pure nickel strips are the material you want, but many vendors swap out it for nickel-plated steel strips, which are poorer and have greater resistance – not suitable for most battery projects. 100% pure nickel strip. verify all of our strips to assure that you are getting the high-quality pure nickel. It also solder incredibly quickly, so you can weld them onto your existing busbar connections to raise the supply of current you can pull through the busbars. The benefits are nearly limitless!
battery enclosure
Design Benefits
• Up to 50 percent lighter than an equivalent steel design
• Best-in-class mass energy density at more than 160 watt-hours per kilogram, an extremely efficient design for OEMs and Tier 1 battery pack manufacturers.
• Accommodates all battery cell types and is designed particularly for battery electric vehicles with larger power packs such as pick-up trucks, sport utility vehicles and crossovers.
• Most cost-effective aluminum solution for mass production electric vehicles when compared to aluminum extrusion and casting-intense designs.
• Low price premium on $/kg saved compared to equivalent steel designs at substantially lower weight.
https://www.novelis.com/automotive/electric-vehicle-battery-enclosure/
as we know now
Power (p)= Voltage (v) * Current (i) kw
Power=3.3 *2.5 =8.25 kw
To get 18kwh we are assuming 48s 48p
i.e; 48*48 =2304 cells
series connection gives 48*3.3 =158.4 v
parallel connection gives 48* 2.5 =120 A
from this we can get
158.4* 120 =19.008 kwh energy or capacity.
we design battery pack for 48s and 48p cell along wth battery spacers to hold cells and for their connection nickel strip is used
when cells are connected by nickel strip spot welding should be used so that cell not get damage.
Result:
|
Calculation Parameter |
Value get |
|
Single Cell Energy (Wh) |
8.58KW |
|
Volumetric energy (Wh/m^3) |
248.62 Wh/m^3 |
|
Gravimetric energy (Wh/kg) |
112.89 Wh/kg |
|
Total number of cells for battery pack |
2112cells |
|
Mass of battery pack |
160.512 kg |
|
Total volume of the battery pack |
72.89 m^3 |
|
Cell peak current (A) |
52A |
|
Battery pack peak current (A) |
2496A |
|
Battery pack peak power (W) |
3624192 or 362.42 W |
|
Cell continuous current (A) |
26A |
|
Battery pack continuous current (A) |
1248A |
|
Battery pack continuous power (W) |
18120.96 or 18.120 Kwh |