Project 1 Mechanical design of battery pack
Battery pack capacity: 18 kWh
Cell: ANR26650M1-B
Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.
Aim:-To develope a battery pack of 18kWh using ANR26650M1-B cells along with there mechnical design.
Datasheet: Lithium Werks’ 26650 cells are best for Power.Safety.Life.™ applications. They deliver very high power due to their use of patented Nanophosphate® battery technology. Based on lithium iron phosphate chemistry (LiFePO4), the cells are inherently safe over a wide range of temperatures and conditions. Whether the application requires outstanding cycle life or stable float reliability, the Lithium Werks’ 26650 cells are suitable for a wide variety of power, pulse, or stand-by applications.
Nanophosphate® Technology 26650 Lithium Ion Power Cell Nanophosphate® battery technology offers thermal-stable chemistry, faster charging, consistent output, low capacity loss over time, and superior total cost of ownership (TCO). 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 lithium-ion chemistries.
Features: The ANR26650M1-B is the next generation A123 system's pioneering 26650 cylindrical cell, now with greater power & energy density & lower impedence. This versatile lithium ion cell is suitable for wide variety of applications & system designs. Proven performance in the toughest conditions, combining durability, reliability, & safety, the ANR26650M1-B cell offers an excellent combination of price-performance.
Battery specifications:
Cell Characterstics/Data:
Testing of a cell:
Dimension of a cell:
Cell applications:
- Energy storage
- Frequency regulation
- Uninterruptible Power Supplies
- Communication technologies
- Aviation/Aerospace
- Electrified mobility devices
- Industrial equipment
- Medical devices
- Consumer Products.
Cell Calculations:
This calculation is to determine how much space of volume the cell will take in the to have the capacity of 18kw.
Cell energy = Nominal volatge * nominal cell capacity
∴Cell energy=3.3*2.5
=8.25Wh
∴So each cell has the energy of 8.25 wh.
Cell Volume = π *r^2*h
∴Cell Volume=3.14*0.013*0.13*0.065
=0.0344929 m^3
So, now we have to calculate how much Watt per volume the cell can produce:
Cell energy density = Cell energy/Cell volume
∴Cell energy density = 8.25/0.0344929 Wh/m^3
=239.17 wh/m^3.
Battery pack Calculations:
To get 18 kWh as a output power we have to consider series and parallel cells to be connected to create the battery pack module of the required capacity.For design and calculation of battery pack here, i assume a vehicle to achieve 200km in 18 KWh battery pack also i assume 145.2 nominal voltage for series connection.
Assumptions,
Vehicle Range = 200 Km
Battery Pack Capacity = 18KWh
Now,
a) We will calculate per Km average energy requirement = 18000 (Wh)/200 (Km)
= 90Wh/Km
∴Battery Pack Total Energy = Average energy * km
= 90Wh/km * 200km
= 18000 Wh
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.
b) Number of cell connected in series = Nominal voltage of series connection/nominal voltage of a single cell
= 145.2V/ 3.3V
= 44 cells
44 cells will be connected in a series connection to provide a proper voltage.
c) Energy for battery pack (Wh) = Number of cell connected in series * Single cell energy
= 44* 8.25Wh
= 363 Wh
d) Number of cell connected in parallel = Battery pack total energy (Wh) /energy for battery pack (Wh)
= 18120.96 Wh/363 Wh
= 50 cells
50 cells will be connected in a parallel to provide a proper capacity power.
e) Battery Pack Total Energy (Wh) = No. of cell connected in parallel * energy for battery pack
= 50* 363 Wh
= 18.150 KWh
f) Battery Pack Capacity (Ah) = No. of cell connected in parallel * single cell capacity (Ah)
= 50*2.5 Ah
= 125 Ah
The value of battery pack capacity is used for the total power required by the vehicle.
g) Total Number of Cell for Battery Pack = No. of cell connected in parallel * number of cell connected in series
= 50*44
=2200 cells
2200 cells will be used to make a complete battery pack.
h) Mass of Battery Pack = Total number of cell for battery pack * mass of single cell
= 2200 * 0.076 kg
= 167.2 kg
167.2 kg its the total weight of cell connected in parallel and series.
i) Total Volume of the Battery Pack = Total number of cell for battery pack * volume of single cell
= 2200 * 0.0345 m^3
= 75.9 m^3
75.9 m^3 its the volume occupied by total cell used in battey pack.
j) Cell Peak Current(A) = C rate(max pulse charge current)* single cell capacity
= 20* 2.5
= 50A
k) Battery Pack Peak Current(A) = cell peak current(A) * no. of cell connected in parallel
=50*50
= 2500A
l) battery pack peak power(W) = Battery pack peak current(A) * voltage of series connection
= 2500 A * 145.2
= 363 KW
m) cell continuous current(A) = C rate (max continuous charge current) * single cell capacity
= 10* 2.5
= 25 A
n) battery pack continuous current(A) = cell continuous current(A) * no. of cell connected in parallel
= 25*50
= 1250 A
o) battery pack continuous power(W) = Battery pack continuous current(A) * voltage of series connection
= 1250 A * 145.2
= 181.5 KW
Now we know the weight and volume of the battery pack of 18kWh.So, we will consturct the battery pack.
Battery Pack:
- 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, 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 electrically connected to form a battery pack.
- There are several types of batteries (chemistry) used in hybrid and electric vehicle propulsion systems but we are going to consider only Lithium-ion cells. The main reason is that Li-ion batteries have higher specific energy [Wh/kg] and specific power [W/kg] compared with other types.
There are three basic types of battery cells used in electric vehicles: cylindrical cells, prismatic cells, and pouch cells.
Battery Pack construction:
There are 3 steps for the construction of the battery pack.
1)Battery holding and providing the spacing between the battries.
2)Connecting the battries with the strips (Series or Parallel)
3)making and manifacturing the battery enclosure housing with the thermal managment system and BMS.
1)Holding and spacing:
- Each of the cells are now need to be connected so that it could form a big battery module.
- So, this holds are very importatnt to provide the space between the battery and holding the battries in the correct manner.
- The cells has a vent at the end cap of the cell & should not be covered by any mechinical means.Blocking the cell vent and then sufficiently abusing the cell so as to built the pressure in cell.There must be minimum of 1mm spacing between each cells to allow the vent to open under the fault condition.
- Holders will make it easy to palcethe contact plate between the cells.
2) Connecting the cells:
- When the cells are plalced in the holders ,then the cells need to be connect in the proper manner in series or parallel to get the desired results.
- Ususally a nickle strip is used between the cells to make the conatct.
- 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!
3)Battery enclosure and thermal managment of battery and BMS:
- The battery encolsure is the final protection of the battery.
- So the battery enclose must be very strong and light in weight.
- In the case of any accident the batteries has the tendentcy of catch fire if it get leaked during the car crash,so the battery modle is enclose in a very strong encolsure due to the safety.
- The weight should be less so we can get the best pssible range.
- In this metal housing there is a temperature managment system provided to cool and heat the battries when there is a need to get the best performace of the battries.
- There a several numbers of models connected in series and parallel to build a entire battry pack.
BMS: A battery management system (BMS) is an electronic system that manages a lithium battery pack and the main functionalities are:
- Monitors all of the parallel groups in the battery pack and disconnect it from the input power source when fully charged.
- Balance all the cells voltage equally.
- Doesn't allow the pack from over-discharged.
Final Overview of battery pack enclosure: In the following figure we can see the arrangement of modules of the battery pack which are used in electric vehicles and according to the company vehicle designs the arrangement may be varied.
So, the enclosure procedure, the electrical and the mechanical parameters of the battery pack are also calculated of the ANR26650M1-B is done with the relevent images.
Conclusion:Thus we have studied how to model a battery pack for 18kw battery.