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.

In this Project we are going to calculate the all parameters wjich are requirements for the build EV battery pack. We are going to use the cell ANR26650M1-B for our battery pack.In Parameters we will consider all electrical aspects like temperature,Depth of Discharge ,opeartion current, energy density, workcycle, battery capacity,state of charge,state of health ,Ampere -hour Ah capacity.We also calculate all geometrical consideration like size ,weight,volume ,area .In the end we consider some enclosure model of the battery pack

• Calculating all parameters for 18 Kwh Battery Pack.
• Calculating all Physical dimensions for Battery Pack
• Collecting the data of cell ANR22650M1-B from the Nanophosphate High Power Lithium Ion Cell
• Consider perfect enclosure for the dimensions that we calculated for the battery pack.

• To Build the battery pack for any Electric Vehicle we have to calculate the first proportion of the motor power, and depend on that we will model the battery pack so we know how much power we required which is 18KWh
• For the 18KWh battery pack we have to calculate how many cells are parallel and how many cells in series.
• After calculation of the series and parallel combination we have to calculate the proper geometry and topology consideration for the assembling battery.
• After Assembly we need to find a proper enclosure for teh battery pack for the thermal consideration and other physical damages.

A Battery consists of one or more electrochemical cells which are converting chemical energy into electrical energy during discharging and electrical energy into chemical energy during charging .This type of elements conatined 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 case or enclosure.For atomotive application there are different types cell used individual battery cells are grouped into a single mechanical and electrical unit is called a battery module .The modules are electrically connected to from a battery pack.

The voltage level of the battery determines the maximum electrical power which can be delivered continously .Power is the product between voltage and current P=V*I

The higher the current the bigger the diameter of the high voltage wires and the higher the thermal losses .For this reason the current should be limited to a maximum and the nominal power obtained by having a higher voltage .For our application we are going to consider a nominal voltage of 400V the energy needed for propulsion the high voltage battery must supply th eenergy for the vehicle auxilary devices like 12V electrical system , heating , cooling .Also we have to consider the efficiency of the powertrain during the conversion from electrical energy to mechanival energy.

• First we have to start with cell calculation
• Then we will do the battery pack assumptions
• After assumptions we have to do battery pack calculation
• From cell Dimension we have calculate the surface required for a battery pack
• Depending upon the above calculations we build battery pack construction.

Lithium werks 26650 cells are capable of delivering very high power due to its use of patented Nanophosophate battrey technology .Based on the lithium ion phosphate chemistry the cells are inherntly safe over a wide range of temperature and conditions .Whether the application requires outstanding cycle aor stable float reliability the lithium werks 22650 cells are suitable for a wide variety of power , pulse, stand by applications .Nanophosphate technolgy 22650Lithium ion power cell Nanophosphate battery technolgy offers stable chemistry faster charging , consinet output , excellent cycle life and superior cost performance .It provides the foundation for safe system while meeting the most demanding customer requirements .Multiple layer of protection are employed at the chemistry cell and system level to achieve an energy storage solution with superior safety and abuse tolerance compared to metal oxide lithium ion chemistry.

Cell Calculation

• Volume of the cell

For the Calculation of the volume of the cel we use the formula volume of the cylinder so the formula is 7r r2 h from datasheet od the cell , we have Y and values r=0.013m

and h=0.065m=Volume of the cell Irr2h 3.14 0.0132 0.065 .The volume of the cell is 0.0000344929m3 Basically the value of the volume of the cell is used to find out the total volume of the battery pack.

• Cell Energy

Cell Capacity (Ah )x Cell Voltage (V) = 2.5x3.3=8.25wh cell energy is 8.25wh.

• Single Cell Energy Density Volumetric Energy (Wh/m3)=Single cell energy/Volume of the each of the cell 8.25Wh/0.0000344929m3=2.39179.6572Wh/m3

Battery Pack Assumption

There are 50 cells are in series and 44 cells are in parallel and as above mentioned we are going to use cell ANR26650M1-B this cells

• Total No of the cells : Series * Parallel Cells = 50x44=2200
• Voltage = No of cells in series , nominal voltage = 509.3=165V
• Current = No of parallel cells x cell capacity = 44+2.5=110Ah
• Energy = Voltage current =165 x 110 = 18150WAh
• Total Volume =No of the cells Volume of the single cell = 2200 0.0000344929 = 0.075884381713
• Weight = No of the cells x weight of single cell = 2200 0.076 = 167.2kg
• Energy Density= Volume x battery pack energy = 0.07588438x 18150 = 1.377.301497kiNh/m^3

The assembly of the full battery pack with 50S/44P

The Arrangement of the pack is as follow

2112 cells will have 50S/44P here we arrange the pack such that it will build a proper battery pack.

Technical Specification of 2112 Battery Pack i

• Package - 50S/44P
• Capacity - 110 Ah
• Voltage - 165V
• Weight - 167.2 kg
• No of cells - 2100
• Power - 18.5Kwh

Cells come in fixed voltages and capacity .If you need more voltage you can deal with multiples of the cell voltgaes .Cells capacities do vary particularly with a supplier power stream that has a great variety of cells size available but voltages don't.All Nicad or NiMh cells are 1.2 volts nominal lead acid is 2.0 volts and the various lithium technologies are about 3.6volts per cell .If you need more voltages you have to add them in series if you need less voltages you need some kind of voltage regulator or DC/DC converter

Geometry and Topology Consideration for Asembly Battery

There are infinite variety of battery pack combinations.

• Ladder, Linear ,F type or radial

The straps will both come off the top when there are an even number of cells and one off the top the other off the bottom when there is an odd number cells .With a connector and heat shrink wrap.

• Multi Row Cells

There are two ways to start packing them .One could be called the cubic and the other face centered cubic or nested.

Cubic packing is in neat rows .The size of such a pack is nDx mD x H where n is the number of cells in a row m is the number of the rows D is the cell diameter and H is the cell height

• Face Centered Cubic

Face Centered cubic packing is nested to take up less room. Calculating the size takes a little geometry which are

• FCC with Alternating Long and Short rows

If there are alternating long and short rows such as 3,4,3 ten cell pack the formulas

• Fixed Channel width Optimization

What if you have a fixed width channel and want to stagger the cells to maximize the number of the cells per unit width .

• Packing cells in a tube 3 cells

For a cell pack you can put the cells in tube

The diameter of the outer circle is 2.16D

• Packaing cells in tube 4 cells

For a four cell pack in a circulat tube

Injection Molded Plastic

Enclosure made from injection molded plastics are most commonly used for battery packs.For these enclosure pack design two or more plastic parts are molded and then assembled with the pack and accompained circuitry.They can be sealed using glue, mechanical fastners or ultrasonic welding. The product cost be reduced by using insert moldings in which the interconnection strips and the terminals are moulded into the plastic parts to eliminate both materials and assemble costs.

In some design the batter pack can form part of the outer case of the end product and usually requirement a mechanical latch to hold a battery in place . This latch as well as the terminals must interface with plastic parts from the device itself precesion and tight tolearnce are essential

Shrink Wrap Or Vaccum Formed Plastic

The simplest and least expensive ackaging fro small battery is shrink wrap or vaccum formed plastic .These solutions are only possible if the battery is intended to be completely enclosed by the finished product.In other cases battery pack are mounted externally and may serve a mechanical function such as handle or base for the product .Our extensive experience in designing battery enclosure of all types allow us to enhance the functional deisgn of the product while assuring the battery passes any shock vibration and environmental testing required for your application.

Other Consideration

Thermal effects need to be taken into account and tolerance must allow for potential swelling of the cells .Some Lithium pouch cells may swell as much as 10% ar more over the lifetime of the cell.For this reason enclosure may be designed with vent holes to dissipate generated heat or exhaust vented gases from cells .Multiple vent holes may be used to increase airflow in and out of the pack.

Intrinsically safe battery

Intrinsically safe battery will not initiate and explosion should the electronic device malfunction while operating in areas that contain explosive gases or high dust concentration .For these application specific materials are selected for battery pack enclosure and many times potting material is used in the battery pack enclosure to eliminate any air gaps.