Project 1 Mechanical design of battery pack
Calculation :
Total energy needed = 18kwh = 18000wh
Cell voltage = 3.3V
Cell capacity = 2.5Ah
Cell energy = Nominal volatge * niminal cell capacity
Cell energy=3.3*2.5 = 8.25Wh
No. of the cell = 18000/8.25 = 2182
let battery voltage as 200v
No. of series cell = 200/3.3 =60.60 = 61
No. of parallel cell = 2182/61= 35
61s35p
Cell Volume = π*r*r*h
=3.14*0.013*0.013*0.065
=3.44m = 0.0344m^3
Cell energy density = cell energy/cell volume
=8.25/0.0344 Wh/m^3
=2.470 wh/m^3
Battery pack.
let us consider 61 cells connected in series a and 35 cells connected in parallel.
toatal number of cells = 61*35=2135 cells
Voltage of the battery pack=Nominal volatge *cell connecetd in series
=3.3*61
Voltage of the battery pack = 201
current capacity of the battery pack=Cell capacity*Cells connected in parallel
=2.5*35
=88Ah
The total energy of the battery pack=Volatage *current capacity
201*88 = 17688
=17.7KW
Total volume =Cell volume*Total no of cells
0.0344*2182
=75.06m^3
total weight of the battery=Total no of cells*Weight of each cell
2182*0.076 kg
total weight of the battery = 165.832Kg
Drawing cell model:
Each of the cells are now need to be connected so that it could form a big battery module.
So this holdes are very importatnt to provide the gapping between the battery and holding the battries in the correct manner.
The cells has a vent at the end cap of the cell.and 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.
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.
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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.