Project 1 Mechanical design of battery pack

In this project , we are going to calculate all the parameters which are required to build electric vehicle battery pack. Here we are going to use Cell ANR26650M1-B for our battery pack by considering all the electrical aspects like temperature,Depth of discharge , state of charge , energy density , work cycle etc.

The high voltage battery is one of the most important components of a battery electric vehicle. The battery parameters have a significant influences like :-

1.Maximum motor torque

2.Vehicle range

3.Vehicle total weight

4.Vehicle price , etc

A battery consist of one or more electrochemical cells which are converting chemical energy to elctrical energy during dischargeing and vice vera during charging mode. It consist of five majr components like anode , cathode , separator, terminals , electrolytes and a case encloser. A cell refers to a single anode and cathode separeted by some electrolytes used to produce voltage and current.

Lithium ion phosphate has the battery technology that delivers high power and good energy density. The battery pack is a set of identical or individuals battery cells . They may be configurd in series , parallel or in a mixture way to deliver desired voltage , capacity etc. Lithium ion phosphate offers good electrochemical performance with low resistance. It has a higher self-discharge than Li-ions batteries.

Cell: ANR26650M1-B specifications :-

Volatge = 3.3 V

capacity = 2.5 Ah

Energy = 8.25 Wh

Specific power = 2600 W/kg

Life cycle = >4000 cycles

Temperature = -30c - 50c

Mass = 76 g

Cell diameter = 0.026 mm

Here we want to build 18 Kwh battery.

So,lets assume the voltage of battery pack is 300 V.

Power = Volatge * Current

Pack capacity = Energy capacity / Pack voltage

= 18000 / 300

= 60 Ah

No. of cells connected in series = Pack volatge / Cell voltage

= 300 / 3.3

= 90.90 = 91 cells

No. of cells connected in parallel = Pack capacity / Cell capacity

= 60 / 2.5

= 24 cells

Total no of cells in battery pack = No. of cells connected in series * No. of cells connected in parallel

= 91 * 24

= 2184 cells

Total energy of the pack = Pack volatge * Pack capacity

= 300 * 60 = 18 Kwh

so, the battery pack having 18 kwh capacity has a 91S24P configuration.

Weight of the battery pack = Total no of cells * Cell weight

= 2184 * 76 = 166 kg

Length of battery pack = No. of cells connected in series * Cell diameter

= 91 * 0.026

= 2.36 m

Width of battery pack = No. of cells connected in parallel * Cell diameter

= 24 * 0.026

= 0.624 m

Area of the battery pack = Length of battery pack * Width of battery pack

= 2.36 * 0.624

= 1.472 m^2

Volume of the battery pack = Area of the battery pack * Cell height

= 1.472 * 0.065

= 95.5 L

Specific energy density = Energy of the pack / Weight of the battery pack

= 18000 / 166

= 108.43 Wh/Kg

Volumetric energy density = Energy of the pack / Volume of the battery pack

= 18000 / 95.5

= 188.25 Wh/L

Cost of battery pack = Total no of cells in battery pack * Cost of each cell

= 2184 * $ 6.55

= $ 14305.2 = Rs 10,72,890

DESIGN :-

CELL CONFIGURATION :-

Series connection :- Here the batteries are connected in end to end way (Positive of one is connected to negative of other) where we can increase the volatge value by current value to reamin constant .

Parallel connection :- Here batteries are connected in all positive terminal one side and all negative terminal other side by not changing the volatge value where current values can be varies .

We can assemble the battery pack by connecting all the battery holders to form a well structure of battery as it provides a uniform distance between all the batteries though receives less vibration . Then we use some types of nickel strips to connect them and some welding are also done so that they can connect eletcrically and produce a desired volatge and current value .

Hence, here we calculated some parameters for battery pack deign in electric vehicles and its overall constructions .