Project 1 Mechanical design of battery pack

Aim:-

To develop a mechanical design of battery pack of capacity 18 kWh by using the ANR26650m1-B cell.

Description:-

ANR26650M1-B Cell:-

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. These 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 the systems to meet end-of-life power and energy requirements with minimal pack oversizing.

Application:-

These cells are used in commertial, Govenments, Grid and Transportation solutions. The details are attached as image for your references.

Datasheet:-

Constant power discharge characteristics plot:-

Life Cycle Performance plot:-

Cell:-

The cell we use here is ANR26650M1-B is A123 System which is suitable for vide variety of applications and system design.

Battery Pack:-

A battery pack is a set of any number of cells which are configured in series or parallel or series parallel to deliver desired voltage, current and power density

Mechanical Design of battery pack:-

The battery is one of the most important component of battery electric vehicle. The parameters of battery will have an impact on other components and the vehicle attributes such as Motor Torque, Brake Torque, Vehicle range, Toatal vehicle weight and Vehicle price

For designing an battery for an elecvtric vehicle the following input parameters are to be choosen carefully as per the requirement which are Chemistry of battery, Voltage, Average energy consumption of vehicle on a driving cycle and Vehicle range.

A battery is a combination of one or more electrochemical cells which converts chemical energy to electrical energy during discharge cycle and electrical energy to chemical energy during charging cycle.This defines the chemistry of battery.

Battery contains Electrodes-Anode and Cathode, Separators, Terminals, Electrolyte and an Encloser to protect from environmental impact. For EV different types of cells based on size and shape are used. Here we have choosen a Cyclindrical cell.

Among different chemical types of battery availability we have choosen lithium ion since it has higher specific energy and specific power.

EV Design - Battery Calculation:-

Battery pack Calculation:

Battery Pack Capacity = 18 kWh = 18000 Wh

Nominal Voltage of a cell = 3.3 V

Let us assume that, Battery Pack Voltage = 500 V

No of Cells (N) = Total Pack Capacity/(Nominal Voltage of a cell*capacity of a cell) = 18000/(3.3*2.5) = 2182

That is minimum 2182 cells are required to make 18 kWh of energy.

To calculate the configuration of cells based on pack voltage which is 500 V,

Number of cells in series (to produce 500 V) = Required Voltage / Nominal voltage of a cell = 500/3.3 = 151.51 = 152

Here 152 cells are connected in series 

Calculate parallel configuration,

Number of cells in parallel = Total no.of cells / Number of cells in series = 2182/152 = 15

So 15 parallel connections are made.

Thus the battery pack configuration is 152S15P

Total no of cells used are 2280 cells

The total battery pack capacity of the configuration can be calculated,

Battery capacity to deliver current in Ah = 15 * 2.5 = 37.5 Ah

The battery pack can supply 37.5 A current for a period of 1 hour which is 1C C-rate.

Range:-

The range the battery pack can be calculated as,

let us assume that the energy consumption from the battery is 200 Wh/km at 80% efficiency of the powertrain

Range = Total pack Capacity/energy consumed per km = 18000/200 = 90kms

Thus the range it is capable of delivering energy is 90 kms.

Battery Diamensions:-

 

ANR26650 Cell has 26mm diameter and 65 mm height on considering the size of battery and spacing required we need to choose the size of casing for the battery.

Length of Case,L = number of cells in series*(cell diameter + margin at both sides of cell)+clearance = 152*(26+4)+60 = 4620 mm.

Breadth of case,B = number of cells in parallel*(cell diameter + margin at both sides of cell)+clearance = 15*(26+4)+60 = 510 mm.

Height of case,H = Height of cells + clearance (Wiring, Metal Strips and Cell holder clearance) = 65 + 60 = 125 mm

Weight of Battery:-

Cell Weight = 76 g

Number of cells = 2280

Battery pack weight (W) = cell weight*number of cells+weight of accessories = 0.076*2280+4.5 = 173.28+4.5 = 177.78 kg

Cyclindrical Battery Pack Assembly:-

Product	Description
Battery Tester	5V, 2Ato 6A battery tester
Battery Sorting Machine	Based on output the battery is sorted using data record function
Manual Spot Welding Machine	AC Spot Welding(Either Single welding point or Double welding point)
BMS Tester	Over-Charging and discharging current and voltage testing
Battery Comprehensive tester	Battery pack comprehensive tester (100V 120A)

Conclusion:-

The lithium ion are great power source for EV application but they require protective circuit since they are volatile in nature hence it has to be operated with proper protective circuits such as BMS for protecting it during charging and discharging.