Project 1 Mechanical design of battery pack

Aim

To create 18Kwh battery pack model with no of parallel and series cells

Here the given example model of LiFePo4(lithium iron phosphate) battery

Nanophosphate® High Power LithiumIon Cell ANR26650M1-B

A123’s high-performance Nanophosphate® lithium iron phosphate (LiFePO4) battery technology delivers high power and energy density combined with excellent safety performance and extensive life cycling in a lighter weight, more compact package. Our cells have low capacity loss and impedance growth over time as well as high usable energy over a wide state of charge (SOC) range, allowing our systems to meet end-of-life power and energy requirements with minimal pack oversizing.

The nanophosphate discharge rate has been given at a rate of

current discharge rate at 23 C

Cycle performance at 100% DOD

Battery cell dimensions

From the above datasheet we can take the required dimensions to build the model

While for assumption has taken as = 18kwh and voltage = 350V

Now we have to build the battery pack for the assumption vehicle the energy has taken as 18Kwh as given

1)No of cells need for the model

N = Energy/(nominal volt * nominal capacity) for datasheet

N = 18000/(3.3*2.5) = 2180 cells.

So for the 18kwh battery pack we need 2180 no of cells for a fully constructed pack

So the battery consists a combination of both parallel and series connection so we need to identify no of parallel and series cells for that

2) Series connection

No of cells connected in Series = volt required/volt of one cell

Ncs = 350/3.3(from data) = 106 cells needs to connected in series

Then no of parallel connection

3) Parallel connection

no of cells connected on parallel = total no of cells / Ncs

Ncp = 2180/106 = 20 cells requires to connected in parallel

Now we can build the battery pack with no of series and parallel connection so the our battery model would be 106s20p model

Now we can find the battery capacity

3) capacity

battery capacity = Ncp * cell capacity

Battery capacity = 20*2.5 = 50 Ah

Now we can know the dimension of the cells by finding Length,height for the pack model

4) Length of battery pack

Length = Ncs*(dia of cell + margin of sides)

Length of pack = 3180mm

5)Height of battery pack

height of the battery pack = (height of cell + height of the battery connector)

Height = ( 65+25) = 90mm

6)Width of battery

width of the pack = Ncp *(cell dia + margin of sides)

Width of the pack = 600mm

• Here the height of the battery connector considered as 25 mm after the pack has soldered together with copper and with plastic connector