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, DOD, Operation current, Energy density, Work cycles, Battery capacity, SOC, SOH, Ah capacity. We also calculate all geometrical consideration 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 nanophosphate high power lithiumion cell PDF.
2)Calculating all electrical parameters for 18/ Kwh battery pack.
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 attribyres of the vehicle like:
- maximum traction motor torque
- maximum regenration brake torque
- vehicle total weight
- vehicle price
Pretty much all major aspects of a pure electic 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 enrgy into mechanical energy into electrical energy (during discharging). and elecrical energy into chemical energy (during charging). The type of elements contained within a battery and the chemical reactions during discharging-charginh events define the chemistry of a battery.
A battery cell consists of five major components :
1. Electodes- Anode and cathod
2. Seperators
3. Terminals
4. Electrolyte
5. a case or enclosure
for aurtomotive applications there are different types of cells used individual battery cells are grouped into a single mechanical and electical unit called a battery module. The modules are electrically connected to form a battery pack.
The voltage level of the battery determines the maximum elecrtical power which can be deliverd contineously. Power P (W) is the product between Voltage(V) and current I(A).
so, P = V*I
The higher the current the bigger the diameter of the high voltage wires and the higher the thermal losses. For this reason the current should be limited to a maximum and the nominal power obtained by having a higher voltage for our application we are going to consider a nominal voltage of 400V.
The energy needed for propulsion the high voltage battery must supply the energy for the vehicles auxiliary devices Eaux[Wh/Km], like 12 v electrical system heating, cooling etc.
Also we have to consider the efficiency of the powertrain µp [-] during the conversion from electrical energy to mechanical energy.
Battery pack architecture :
All high voltage battery packs are made up from battery cells arranged in strings and modules. A battery cell can be regarded as the smallest division of the voltage.
Individual battery cells may be grouped in parellel and or series as modules. Further, battery modules can be connected in parellel and or series to create a battery pack. Depending on the battery parameters there may be several levels of modularity.
| Manufacturer: | LithiumWerks |
| Mfg PN: | 300732-006 |
| Chemistry: | Lithium Iron Phosphate (LiFePO4) |
| Voltage: | 3.3 Volts |
| Capacity @ 25°C: | 1.25 Ah |
| Energy @ 25°C: | 8.25 Wh |
| Energy @ 25°C: | 8.25 Wh |
| Specific Power: | >4000W/kg | (@ 25°C, 2 sec pulse) |
| Impedance: | >6mΩ | (1kHz AC) Typical) |
| Cycle Life: | > 4000 Cycles | (@ 1C/1C, 100% DOD) |
| Dimensions | |
| Height (max): | 65.15 (+/- 0.5 mm) |
| Diameter (max): | 25.96 (+/- 0.5mm) |
| Mass: | 39.5 (+/- 1.0 g) |
| Warranty: | DOA |
The total battery pack voltage is determine by the number of cells in series. for example the total (string) voltage of 6 cells connected in series will be the sum of their individual voltage.
In order to increase the current capability the battery capacity, more strings have to be connected in parelle. For example, 3 strings connected in parellel will triple the capacity and currrent capability of the battery pack.
Battery pack production Line:-
Procedure :
1) First we have to start with cell calculation
2) Then we will do battery pack assumptions
3) After assumptions we have to do battery pack calculations.
4)Fom the cell dimension we calculate the surface required for a battery pack.
5) Depending upon the above calculation we build battery pack construction.
Following are the all cell (Cell : ANR26650M1-B) parameters for battery pack.
from above all parameters we will calculate further parameters which are used for battery pack construction. Cycle life performance 100% DOD, Various temperature and Discharge Rate of cell.
Dimension of the cells :-
Calculation :
The calculation is to determine how much space of volume the cell will take in to have the capacity of 18Kw
Cell energy = 3.3*2.5
= 8.25Wh
So each cell has the energy of 8.25Wh
Cell volume = Π*r^2*h
= 3.14*0.015^2*0.065
=0.0459225 m^3
So now we have to calculate how much watt per volume the cell can produce :
cell energy density = cell energy/cell volume
= 8.25/0.0459225
= 179.65 Wh/m^3
Now we have to assume the battery pack
To get 18 Kw as a output power we have to cosider series and parallel cell to be connected to create the battery pack module of the required capacity.
so we quired 400 V as a output voltage and each cell nomianal voltage is 3.3 volt.
so to generate 400 volt we require cell = 400/3.3 connect in serires
cell in series = 122
Total Voltage = 122*3.3
= 402.6
now we have a capacity of each cell is 0.5C=2.5 Ah
So C =2.5/2=1.25
so required power output is 18000 Wh, voltage is 400
So, P = VxI
I = P/V
So current required I = 18000/400 = 45Ah
So to generate 45 Amp. we require cell in parellel
Cell in paellel = 45/1.25 = 36 cells
Total Current = 45Ah
So the total number of cell quired= 122*36
= 4392
Total energy of the battery pack = Voltage*Current capacity
= 402.6*45
= 18.1 Kwh
Now we know the total number of cells which are required in the battery pack we can now calculate the energy density, volume and weight of the entire battery pack.
Total volume = Total no. of cells*cell volume
=4392*0.0459225
= 201.69 m^3
and
Total weight of the battery = total no of cells * weight of each cell
= 4392*0.076
= 333.7 Kg is the total weight of battery
Now we know the weight and volume of the battery pack of 18KW So we will construct the battery pack
Battery Pack :
- A battery consist of one or more electrochemical cells, which are converting chemical energy into electrical energy and viceversa during chargin and discharging.
- 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, seperarator, terminals, electrolyte and a case or enclosure.
- Individual battery cells are grouped together into a single mechanical and electrical unit called a battery module.
- The modules are electricaly connected to form a battery pack.
- There are several types of batteries used in hybric and electric populsion system but we are going to consider only lithium oin cells. The main reason is that li-ion batteries have higher specific energy(W/Kg) compared with other types.
EV uses mainly 3 types of cells : Cylindrical prismatic and pouch.
Battery Pack construction :
There are 3 steps for the construction of the battery pack.
1)Battery holding and providing the spacing between the batteries.
2)Connecting the battries with the strips (series or parallel)
3)Making and manufacturing the battery enclosure housing with the thermal management system and BMS
1) Battery holding and specing :
- Each of the cells are now need to be connected so that it could form a big battery module
- So this holdes are very important to provide the gapping between the battery and holding the batteries in the correct manner.
- The cell has a vent at the end of the cell and should not be covered by any mechanical means blocking the cell vent and then sufficiently abusing the cell so as to built the pssure in cell. There must be minimum of 1mm spacin between each cells to allow the vent to open under the fault condition
- Holders will make it easy to palce the contact plate between the cells.
2)Connecting the cells :
- When the cells are placed in the holders, then the cells need to be connect in the proper manner in series or parallel to get the desited results.
- Usually a nickle strip is used between the cells to make the contact.
- 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 rusted after it applies to battery pack.
- It wont affect the current transfer between batteries. _Pure nickel strips are hte material you want, but many vendos swap out it for nickel plated steel strip which are poorer and have greater resistance not suitable for most battery projects 100% pure nickel strip.
3) Battery enclosure and thermal management of battery and BMS
- The battery enclosure is the final protection of the battery
- So the battery enclosure is very strong and light in weight
- In the case of any accident the batteries has the tendency of catch fire if it get leaked during the car crash, so the battery modle is enclose in a very strong enclosue due to the safety.
- The weight should be less so we can get the best possible range
- In this metal housing there is a temperature management system provided o cool an heat the battries when there is a need to get the best performance of the batteries
- There a several numbers of models connected in series and parellel to build a entire battery pack.
BMS :
A battery management system (BMS) is an electronic system that manages a lithium battery pack and the main functionalities are
1. Monitors all of the parallel groups in the battery pack and disconnect it from the input power source when fully charged.
2. Balance all the cells voltage equally
3. Doesnt allow the pack from over discharged.
Results :-
| Sr. No. | Calculated parameters | Qty |
| 1 | Cell volume | 0.0459225 m^3 |
| 2 | cell energy | 8.25 Wh |
| 3 | Cell Density | 179.65 Wh/m^3 |
| 4 | Pack assumptions | 122P36S |
| 5 | Total No. of cells | 4392 |
| 6 | Voltage | 400 |
| 7 | Capacity | 45 Ah |
| 8 | Energy | 18.1 Kwh |
| 9 | Total volume | 201.63 m^3 |
| 10 | Total Density | 789022.8 Wh/m^3 |
| 11 | Weight | 333.7 kg |
Referance :-
https://skill-lync.com/student-projects/project-1-mechanical-design-of-battery-pack-39
file:///C:/Users/Dell/Downloads/MechanicalDesignandPackagingofBatteryPacksforElectricVehicles.pdf