Project 1 Mechanical design of battery pack

AIM: To calculate the utilisation of 18kWh Lithium Iron Phosphate (LiFePo4) Battery pack and make the detailed report for the same.

KEYWORDS: Voltage, Current, Capacity, Life cycle, Li-ion, Constant power, Constant current, etc.,

OBJECTIVE:

1. To study the ANR26650M1-B battery cell along with specification.

2. To calculate the number of cells in series and parallel for the given battery capacity.

3. To calculate the related parameters which affects the performance of battery.

INTRODUCTION:

An electric vehicle (EV) is a vehicle that uses one or more electric motors or traction motors for propulsion. An electric vehicle may be powered through a collector system by electricity from off-vehicle sources, or may be self-contained with a battery, solar panels, fuel cells or an electric generator to convert fuel to electricity. EVs include, but are not limited to, road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft.

A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, with no secondary source of propulsion (e.g. hydrogen fuel cell, internal combustion engine, etc.). BEVs use electric motors and motor controllers instead of internal combustion engines (ICEs) for propulsion. They derive all power from battery packs and thus have no internal combustion engine, fuel cell, or fuel tank. BEVs include – but are not limited to motorcycles, bicycles, scooters, skateboards, railcars, watercraft, forklifts, buses, trucks, and cars. These batteries are usually rechargeable (secondary) batteries, and are typically lithium-ion batteries. These batteries are specifically designed for a high ampere-hour (or kilowatt-hour) capacity.

Comparisons of different types of Li-ion batteries used in EVs from the following perspectives: specific energy (capacity), specific power, safety, performance, life span, and cost (the outer hexagon is most desirable). Lithium Nickel Manganese Cobalt Oxide (NMC), Lithium Iron Phosphate (LiFePO4) and Lithium Manganese Oxide stand out as being superior among these six types.

Here the referred battery cell as ANR26650M1-B - A123’s high-performance Nanophosphate®lithium iron phosphate (LiFePO4) batterytechnology delivers high power and energydensity combined with excellent safetyperformance and extensive life cycling in alighter weight, more compact package. Our cellshave low capacity loss and impedance growthover time as well as high usable energy over awide state of charge (SOC) range, allowing oursystems to meet end-of-life power and energyrequirements with minimal pack oversizing.

APPLICATIONS:

1. Commercial Solution

• Datacenter UPS
• Telecom backup
• IT backup
• Autonomously guided vehicle
• Industrial robotic and material handling equipment
• Medical devices

2. Grid Solution

• Frequency regulation
• Renewables Integration
• Reserve Capacity
• Transmission and distribution

3. Government Solution

• Military vehicles
• Military power grids
• Soldier power
• Directed Energy

4. Transportation Solution

• Commercial vehicles
• Off-highway vehicles
• Passenger vehicles

CALCULATIONS:

Given:

Battery capacity (Eb) = 18 kWh

Diameter of cell (D) = 26 mm

Length of the cell (L) = 65 mm

Mass of the cell (m) = 76 g

Nominal voltage of the cell (Vc) = 3.3 V

Rated capacity (Cc) = 2.5 Ah

For the given data, we can calculate Volume of cylindrical cell,Overall capacity, Volumetric energy density & Gravimetric energy density.

(i) Volume of Cylindrical Cell,(Vcc) = (pi / 4) * D^2 * L

                                                         = (3.142/4) * (26e-3)^2 * (65e-3)

                                                         = 3.45e-5 cubic meter

Note: 1 cubic meter = 1000 ltr

                                                   Vcc = 0.0345 ltr

(ii)  Battery Cell Capacity,(Ebc) = C * V

                                                   = 2.5 * 3.3

                                             Ebc = 8.25 Wh

From the overall battery capacity (18 kWh), we can calculate number of cells in series and parallel.

C = Eb / V

   = 18e3 / 422.4           (since, voltage is taken as per trial and error method)

C = 42.5 Ah

1. Ns = V / Vc                (since, Vc = 3.3 V)

         = 422.4 / 3.3

    Ns = 128 cells

2. Np = C / Cc                (since, Cc = 2.5 Ah)

         = 42.5 / 2.5

   Np = 17 cells

(iii) Volumetric energy density,(Uv) = Ebc / Vcc

                                                          = 8.25 / 0.0345

                                                     Uv = 239.13 Wh/ltr

(iv) Gravimetric energy density,(Ug) = Ebc / m

                                                            = 8.25 / (76e-3)

                                                       Ug = 108.5 Wh/kg

Comparison of Electric Car as per the Battery Capacity:

1. Tata Tigor EV:

Powered by a three-phase AC induction motor, this electric sedan comes in Egyptian Blue and Pearlescent White colour options. The 310-litre boot space is an additional facility that can be very handy while storing luggage.

• Battery Capacity – 21.5kWh
• Distance per Charge – 142km/full charge
• Recharge Time – Fast charging in 90 minutes and normal charging in six hours.
• Price – Starting from Rs.9.54 lakh.
• Frontal Area & Dimension: Length-3992mm, Width-1677mm, Height-1537mm.

2. Mahindra e-Verito:

Another Mahindra offering, the e-Verito is a sedan, unlike the e2o Plus. It is equipped with a similar AC-induction, three-phase motor. Additional features include an electro-hydraulic power steering and tubeless steel wheels.

• Battery Capacity – 21.2kWh
• Distance per Charge – 140km/full charge
• Recharge Time – Fast charging in 1 hour and 45 minutes.
• Price – Starting from Rs.10.11 lakh.
• Frontal Area & Dimension: Length-4247mm, Width-1740mm, Height-1540mm.

Tata Tigor & Mahindra e-Verito are using 21 kWh battery capacity which is near to the given data. So, from the above dimension consider orbitarily and did the further calculation.

Assumptions taken as,

L = 4100 mm

W = 1650 mm

H = 1535 mm

M = 1450 kg

from the above data, we can able to calculate tractive forces in Matlab coding,

clear all
close all
clc
% Reference data for EV,
% Gross weight of an Car
m = 1450;
% Density of a air
pa = 1.293;
% Coefficient of drag
Cd = 0.29;
% Width of an car
W = 1.650;
% Height of an Car
H = 1.535;
% Frontal Area of an Car
Af = W * H;
% Acceleration due to gravity
g = 9.81;
% Coefficient of Rolling resistance
Crr = 0.01285;
% Velocity of a vehicle in KMPH to m/s.
V = [1:1:27.77];

% Calculation of Forces
Fd = 0.5 * Cd * pa * Af * V.^2 ;

Fr = Crr * m * g;

% Conversion of velocity from m/s to kmph
V = V*3.6;

% Plotting the Tire pressure versus Rolling resistance coefficient
plot(V,Fd,'b','LineWidth',2);
xlabel({'Velocity','(KMPH)'},'FontSize',10,'FontWeight','bold','Color','r');
ylabel({'Drag Force','(N)'},'FontSize',10,'FontWeight','bold','Color','r');
title('Velocity vs. Drag Force','FontSize',14,'FontWeight','bold','Color','b')
grid on

RESULTS:

1. Drag Force:

From the above data drag force and Rolling resistance force is calculated.  

2. CC-CV Curve:

3. Cycle Life:

CONCLUSION:

A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, with no secondary source of propulsion (e.g. hydrogen fuel cell, internal combustion engine, etc.). BEVs use electric motors and motor controllers instead of internal combustion engines (ICEs) for propulsion.

The above battery capacity is mainly used for Sedan type passenger car. For laguage and transportation needs around 14 - 15 kWh for example Mahindra treo e-rickshaw.  

REFERENCE:

[1].  S. Panchal, I. Dincer, M. Agelin-Chaab, R. Fraser, and M. Fowler, “Experimental and theoretical investigation of temperature distributions in a prismatic lithium-ion battery,” Int. J. Therm. Sci., vol. 99, pp. 204–212, Jan. 2016.

[2].  M.-Y. Kim, C.-H. Kim, J.-H. Kim, and G.-W. Moon, “A Chain Structure of Switched Capacitor for Improved Cell Balancing Speed of Lithium-Ion Batteries,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 3989–3999, Aug. 2014.

[3].  A. Kuperman, U. Levy, J. Goren, A. Zafransky, and A. Savernin, “Battery Charger for Electric Vehicle Traction Battery Switch Station,” IEEE Trans. Ind. Electron., vol. 60, no. 12, pp. 5391–5399, Dec. 2013.

[4].  A. El Mejdoubi, A. Oukaour, H. Chaoui, H. Gualous, J. Sabor, and Y. Slamani, “State-of-Charge and State-of-Health Lithium-Ion Batteries’ Diagnosis According to Surface Temperature Variation,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 2391–2402, Apr. 2016.

[5].  A. Samba, N. Omar, H. Gualous, Y. Firouz, P. Van den Bossche, J. Van Mierlo, and T. I. Boubekeur, “Development of an Advanced Two-Dimensional Thermal Model for Large size Lithium-ion Pouch Cells,” Electrochim. Acta, vol. 117, pp. 246–254, Jan. 2014.

[6].  S. Goutam, J.-M. Timmermans, N. Omar, P. Bossche, and J. Van Mierlo, “Comparative Study of Surface Temperature Behavior of Commercial Li-Ion Pouch Cells of Different Chemistries and Capacities by Infrared Thermography,” Energies, vol. 8, no. 8, pp. 8175–8192, Aug. 2015.