Project 1 Mechanical design of battery pack

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.

A. To develop a mechanical design of battery pack based on the required energy capacity

Nanophosphate high power lithium ion 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. Applications:

Commercial Solutions:

Advanced lead acid replacement batteries for:

• Datacenter UPS

• Telecom backup

• IT backup

Autonomously guided vehicle (AGV's)

• Industrial robotics and material handling equipment

• Medical devices

Government Solutions:

Military vehicles

Military power grids

• Soldier power

• Directed energy

Grid Solutions:

• Frequency regulation

• Renewables integration

• Reserve capacity

• Transmission and Distribution

Transportaion Solutions:

.Commercial vehicales

. OFF-highway vehicales

. passenger vechicales

ANR26650M1-B Technical data;

Constant power discharge characteristics at 23c;

2.5C Constant current discharge at various temperatures;

Cycle life performace, 100% DOD , Various Temperature and discharge Rates;

About cell;

The LithiumnWerks ANR26650MI-B is the next generation of A123 Systems pioneering 26650 cylindrical cell, now with greater power and energy density and lower impedance. This versatile lithium ion cell is suitable for a wide variety of applications and system designs

About module;

A battery management system (BMS) is any electronic system that manages a rechargeable battery (cell or battery pack), such as by protecting the battery from operating outside its safe operating area, monitoring its state, calculating secondary data, reporting that data, controlling its environment.

Mechanical Design of battery pack:

The high voltage battery it is one of the most important component of a battery electric vehicle (BEV). The battery parameters have a significant influence on other components and attributes of the vehicle, like:

.maximum traction motor torque

.maximum regeneration brake torque

.vehicle range

.vehicle total weight

.vehicle price

Pretty much all major aspects of a pure electric vehicle (EV) depend on the parameters of the high voltage battery.

For our electric vehicle battery design we are going to start from 4 core input parameters:

chemistry

voltage

average energy consumption of the vehicle on a driving cycle

vehicle range

A battery consists of one or more electrochemical cells (battery cells) which are converting chemical energy into electrical energy (during discharging) and electrical energy into chemical energy (during charging). The type of elements contained within a battery and the chemical reactions during discharging-charging events define the chemistry of a battery.

A battery cell consists of five major components electrodes - anode and cathode, separators, terminals, electrolyte and a case or enclosure. For automotive applications there are different types of cells used

Individual battery cells are grouped together into a single mechanical and electrical unit called a battery module. The modules are electrically connected to form a battery pack

There are several types of batteries (chemistry) used in hybrid and electric vehicle propulsion systems but we are going to consider only Lithium-ion cells. The main reason is that Li-ion batteries have higher specific energy. compare with other types.

Assumptions:

Battery energy = 18 kwh

Voltage (to run the vehicle) = 400V

(1) Energy = 18 kWh

(ii) Number of cells (N) energy/ (nominal voltage capacity)

N-18000/(3.3 2.5)

N=2182

We need a minimum of 2182 cells to get 18 kWh energy, now based on that, we need to decide configurati

and parallel

In series configuration capacity remains the same and voltage will be the sum of individual cell voltage.

In a parallel configuration, the voltage remains the same and capacity accumulates.

And we assumed 400 Volts are need to run the vehicle.

The nominal voltage of one cell is 3.3 V

Number of series cells required to produce 400 V (Ns) = voltage required / nominal voltage of one cell

Ns = 400/3.3

Ns=121.21=122

122 cells are connected in series will generate 400 voltage and the capacity of the whole module will be 2.5 A Now we need to find the number of cells which will be connected in a parallel configuration

Np (cell in parallel) = total cell / Ns

Np=2182/122

NP= 17.8=18

Hence we take 18 cells for each parallel row, although it is exceeding the required capacity, that is negligible Cell architecture 122 Series and 18 Parallel = 122518P

(ii) Battery capacity:

We know parallel configured cell multiplies individual cell capacity so.

Capacity = parallel cell row individual cell capacity

Capacity 182.5

Capacity 45 Ah

(iv) Current supplied by the battery

We have already calculated battery capacity which is 45 Ah means it is going to supply 45 A current per hour. w

con be considered as C-rate.

(v) Range:

Let's powertrain energy consumption = 100 Wh/km at 70% powertrain efficiency

Range Capacity/energy consumed per kilometro

Range 18000/100

Range=180 km

So our vehicle will be able to cover around 180 km with current parameters.

(vi) Internal Resistance of Battery.

The entire resistance encountered by a current as if it flows through a battery from the negative terminal to the positive terminal is known as internal resistance of battery

(vii) Battery Dimensions:

ANR26650 cell has 26mm diameter and 65mm height. On the basis of that we need to decide battery size of battery casing

Laser beam welding

Laser beam welding or LBW is a welding technique in which a laser beam provides a concentrated heat source that fuses the materials together.

LBW is commonly performed using keyhole mode welding in which the extreme power density of the laser beam causes the metal to melt and evaporate.

As the metal atoms evaporate from the surface, forces in the opposite direction of the evaporation causes a local vapor pressure. The vapor pressure creates a hole which is known as the keyhole by derressing the molten metal.

Here below show the welding of busbars of cylindrical battery cars

Cells in series connection

Workshop

When you connect cells together in series, it doesn't change the amps or the capacity, it only raises the voltage of the pack. Hooking them up in series means that you connect the positive end

of one cell (or P-group) to the negative end of the other as shown below.

Cells in Parallel connections

If you take several cells and connect their same-type electrodes in parallel, they all will act as though they are one large cell. Also, when you first connect them to each other,

they must be at the same level of charge.

Cell houlders

These houlders are used for houlding the individual cells in a better posture without mis-assemble. The connections can be made accordingly to make series connections and parallel connections to form the required module dimensions.

After installind the cells in a individual module the entire maximum positive terminal and maximum negative terninal are made under single pair of terminals as shown below.

Here shown the cells are arranged and welded without using cell houlders as ;

They are just covered by polimer sheet after the interconnections are made. Mostly connections with cell holders should be recommanded for better safety concerns.

Battery Cabinet arrangements;

Each modules are interconnected in series or parllel according to the requirement and packed as a single large cabinet pack as shown below.

Battery pack arrangement:

Finally the overall battery pack after the arrangement of all cabinet connections with enclosure looks like this as shown below,

Vents holes are present with enclosure for cooling/heating the battery pack temperature according to its environment conditions.

Different cell types are used by different of EV such as Cylindrical, Prismatic,Pouch types. The pack constructions are different for every manufacturers.

Below shown the battery pack constructions process of tesla , bmw and Nissan leaf.