Project 1 Mechanical design of battery pack
Aim:
Mechanical Design Of Battery Pack
Procedure:
Battery pack capacity: 18 kWh
Cell: ANR26650M1-B
Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.
Introduction:
Details of Battery:Nanophosphate Technology 265650 Lithium Ion Power Cell-
Litium ion 26650 cells are capable of delevering very high power due to its use of patented Nanophosphate battery technology.
based on lithium ion phosphate chemistry (LiFePO4), the cells are inherently safe overv a wide range of temperature and conditions.Whether the applications requires outsatnding cycle life or stable float reliability.
Nanophosphate battery technology offers stable chemistry,faster charging ,consistent output,excellent cycle life and superior cost performance.
It provides the foundation for safe systems while meeting the most demanding customer requirements.
Multiple layers of protection are employed at the chemistry,cell and system level to achieve an energy storage solution with superior safety and abuse tolerance compared to metal oxide.
Applications:
1.Energy Storage
2.Uninterruptable Power Supplies
3.Communication technologies
4.Aerospace
5.Electrified mobility devices
6.Industrial equipment
7.Medical devices
8.Toys
Theory of Battery:
What is a cell?
A cell refers to a single anode and cathode separated by electrolyte used to produce a voltage and current. A battery can be made up of one or more cells. A single AA battery, for example, is one cell. Car batteries contain six cells at 2.1 V each.
What is a Battery?
Batteries are a collection of one or more cells whose chemical reactions create a flow of electronics in a circuit.
All batteries are made up of three basic components :an anode (-side)cathode(+side) and some kind of electrolyte.
When the anode and cathode of a battery are connected to a circuit,a chemical reaction takes place between the anode and the electrolyte .This reaction causes electrons to flow through the circuit and back into the cathode where another chemical reaction takes place.When the material in the cathode or anode is consumed or no longer able to be used in the reaction,the battery is unable to produce electricity.
Battery Pack:
Battery packs are any number of individual batteries arranged in series or parallel to provide the required power to electronics devices.The most common type of battery used in battery used in battery packs is lithium ion due to its high power density.They may be configured in a series ,parallel or a mixture of both to deliver the desired voltage,capacity or power density.
1.Energy = 18kwh(required)
2.Number of cells (N)=energy?(nominal voltage*capacity)
N=18000/(3.3*2.5)
=2182
We need a minimum of 2182 cells to get 18kwh energy,now based on that we need to decide configuratuion-series parallel.
In series configuration capacity remains the same and voltage will be the sum of individual cell voltage.
In a parallel configuration,the voltage remains the same and capacity accumulates.
Lets need 330V to run our vehicle.
The nominal voltage of one cell =3.3V
Number of cells required to connected in series connection to produce 330V(Ns)=voltage required /nominal voltage of one cell
Ns=330/3.3
Ns=100
100 cells connected in series will generate 330 voltage and the capacity of whole module will be 2.5Ah.
Now we need to find the number of cells which will be connected in a parallel configuration
Np(cell in parallel)=total cell/Ns
Np=2182/100
Np=21.82
Several cells cant be infracted ,so we take 22 cells for each parallel row,although it is exceeding the required capacity,that is negligible.
Cell architecture = 100series and 22 parallel=100S22P
3.Battery Capacity:
We know parallel configured cell multiples individual cell capacity so,
Capacity=parallel cell row*individual cell capacity so,
Capacity=2.5*22
Capacity=55.0Ah
4.Current supplied by the battery:
We have already calculated battery capacity which is 55.0Ah means it is going to supply 55A current per hour,which can be cinsidered as C-rate.
5.Range:
Lets powertrain energy consumption=129Wh/km at 70% powertrain efficiency
Range=Capacity/energy consumed per kilometer
Range =1800/129
=139Km
So ,our vehicle will be able to cover around 139KM with current parameters.
Internal resistance of battery
The entire resistance encountered by a current as it flows through a battery from the negative terminal to the positive terminal is known as internal resistance of battery.
6.Battery Dimensions:
ANR26650 cell has 26mm diameter and 65mm height.On the basis of that we need to decide battery size of battery casing.
Length of casing(L)=number of cells at mid*(cell diameter(26)+margin at both side of cell(4))+clearence at side (diameter at side (diameter of edged cell+margin)
L=98*30+60
L=3000mm
Breadth of casing(B)=cell diameter(26)+margin at both side of cell(4)+clearence at side (diameter of edged cell+margin)
B=20*30+60
B=660mm
Height of casing(H)=65+35(Height of cell +margin for wiring,cell holders and metal strips)
H=100mm
7.Weight of battery pack
cell weight=76g
No of cells =2182
Battery pack weight(W)=cell weight * number of cells+weight of accesories
W=76*2182+4.5=165.8+4.5=170.3Kg
B.Battery Pack Assembly:
Series/Parallel Batteries:
Battery cells can be connected in series,in parallel and as well as a mixture of both the sreies and parallel.
1.Series Batteries:When in a battery,positive terminal of one cell is connected with the negative terminal of succeeding cell,then the cells are said to be series connected or simply series battery.
If E is the overall emf of the battery combined by n number cells and E1,E2,E3,.....En are the emfs of individual cell
2.parallel Batteries:
When positive terminals of all cells are connected together and similarly negative terminals of these cells connected together in a battery ,then the cells are said to be connected in parallel.These combinations are also referred as parallel batteries.
If emf of each cell is identical ,then the emf of the battery combined by n number of cells connected in parallel,is equal to the emf of each cell.The resultant internal resistance of the combinations
Parallel Connected Batteries
The current delivered by the battery is sum of current delivered by individuals cells.
3.Mixed Grouping of Batteries or Series Parallel Batteries:
The cells in a battery can also be connected in mixture of both series and parallel.
These combinations are some time reffered as series parallel battery.A load can require both voltage and current more than that of an individual battery cell.
For achieving the required load voltage ,the desired numbers of battery cells can be combined in series and for achieving the required load current,desired numbers of these series combinations are connected in parallel.
C.Required Components of Battery Pack assembly Tools:
Required -220 cells ,Nickel strips,PVC heat sink film,Spot welder,Connectors,cell holder and solder.
Step1:We are going to start with snapping square cell holder together.One can use cell terminal blocks ,but they will consume more space than hexagonal holder.
Put insulator gasket on the positive side of cell.
Step2:Now place cells in cell holder matrix.After loading all cells put second cell connector block to other side.
Step3:
Connect cell with nickel strips using spot welder.Series connection will be made by connecting cell positive to cell negative and parallel connection will be made by connecting. same terminals.Weld some nickel strips to terminal cells,which will be later used to attached balancing wire.
Step4:After connections ,stick PVC heat sink film to cell solder balancing wire to terminals and battery management systems current supply wire to battery pack.
Step5:Connect balancing wire pin to BMS and glue it to side of battery pack with BMS.
Step6:Now put battery pack in an enclose,that can be made of plastic,metal or battery pack can be wrapped in a plastic sheet.
Note:Pictures used in the battery pack assembly is just for understanding the purpose,they may not be relevant to battery pack calculation.
The Mechanical battery pack overall view from starting to end:
Conclusion:
Since we have discussed Lithium ion and lithium ion polymer batteries are a great power source for projects but they require care during use and charging.