Project 1 Mechanical design of battery pack

Aim:

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

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

Description:

Specifications if battery ANR26650M1-B

Voltage : 3.3V

Capacity :2.5Ah

Energy:8.25Wh

Specific power :2600 w/kg

Impedence :6 m ohms

Cycle life at 1C/1C,100%,DOD,:4000 cycles

Cell type :26650 Lithium ion power cylindrical cell

Discharging Capacity

Max continous discharge :50A

Max pulse discharge Current >50% SOC :120A

Minimum voltage :2Volts

Temperature :-20C to 55C

Charging

Recommeded standard charge :2.5 Amps

Max charge rate :10Amps

Max pulse charge rate <50% SOC

Float Voltage :3.45

Recommeded charge Vs cut off charge :3.6 VOlts,Taper to 125MA

Temperature:(reducing charging current to 125 ma under 0C )0C to 55C

MECHANICAL

Calculations as per assumptions :18KWh battery pack

Calculations for desigining an 18KWh battery pack,basically 18KWh is basically requried to achieve the vehicel its power range,It is depending on the voltage parameters and ampere hour and capacity.

Here we design a high voltage battery pack for an electric vehicle to achieve to achieve its range 220 km.For this calculation,I assumed 145.2V a nominal voltaeg foe series connection.

Basically the value of the voltage of the cell is used to find out the total volume of the battery pack

= Single cell energy

=Cell capacity(Ah)*Cell Voltage (V)

=2.6*3.3

=8.58Wh

The value of the single cell is used to calculate the total energy of the battery pack

-Single Cell energy density

Volumetric energy(Ah/m^3)=Single cell energy/Volume of each cell

=8.58/0.03451 m^3

=248.62 Wh/m^3

Gravimetric energy (Wh/kg)= Single cell energy/Single Cell mass

= 8.58/0.076kg

=112.89 Wh/Kg

Calculation of high voltage battery pack

For design and calculation of battery pack here,I assume a vehicle to achieve 250 km in18 KWh battery pack,also assume 145.2 nominal voltage for series connection

So,

Vehicle range = 250Km

Battery pack capacity =181.121 KWh

Now,

We will calculate per km average energy =18120.96/250

= 72.483 Wh/Km

Therefore,

Battery pack total energy = average energy *km

=72.483*250

=18120.96Wh or 18.120 Kwh

Lets assume the nominal voltage for series connection =145.2V,Basically this depemds up on the motor power,we can decide the values according to the motor

-No of cells connected in series

-Nominal voltage of series connectin?nomial voltaeg of a single cell

= 145.2v/3.3V

=44

44 cells will be connected in series to provide a proper voltage

- Energy for battery pack

-No of cells connected on series * Single Cell energy

=44*8.58Wh

=377.52Wh

--No of cells connected in parallel

-Battey pack totaal enery(Wh)/Energy For battery pack (Wh)

=18120.96/377.52

= 48

---48 cells are connected in parallel to provide a proper capacity power

-Battery pack total energy (wh)

-No of cells connected in parallel * energy for battery pack(wh)

=48*377.52

= 18120.96 or 18.120KWh

Battery pack capacity

-No of cells conneted in parallel * Single Cell capacity

=48/2.6Ah

=124.8Ah

The value of the battery pack capacity is used for the total power requried by the vehicle

--Total no of cells for the battery pack

= No of cells connected in parallel*No of cells connected in series

=44*48

=2112

2112 cells are used to make the battery pack

-- Mass of the battery pack

=Total no of cells for the battery pack * mass of the single cell

2112*0.076Kg

=160.512Kg

It is the total weight of cells connected in paralle and series

--Total volume of the battery pack

-Total no of cells for battery pack* Volume of single cell

2112*0.0345

=72.89m^3

This is the volume of the 2112 cell which is used in the battery pack system

--Cell peak current (A)

=C rate (Max Pulse charge Current)*Single cell capacity

=20*2.6

=52A

--Battery peak current (A)

=Cell peak current * No of cells connected in parallel

=52*48

=2496A

It is used for the operation of the battery pack

--Battery pack peak power (W)

-Battery pack peak current*Voltage of series Connection

=2496A*145.2

=3624192 or 362.42W

-Cell continous current

Crate(Max Contionous charge Current)* Single cell capacity

=10*2.6

=26A

-- Battery pack continous current (A)

=Cell continous current * No of cells connected in parallel

=26*48

=1248A

This is the power which is supply continoue to the whole battery pack system

--Battery pack continous power(W)

=Battery pack continous power*Voltage of series Connection

=1248*145.2

=18120.96 Or 18.120Kwh

Detailed battery pack with its enclosure:

NICKEL STRIPS :

Nickel strips are generally used in battery building.It is due to its efficiency of usage in spot welding and soldering as well of its high corossion resistance over time.It has good properties and excellent resistance to many corrosive environments.The pure nickel will never get rust after it is applied to battery packs.It wont affect the current transfer between batteries.

Pure nickel strips are the material you want but many vendors swap out it for nickel plated steel strips,which are poorer and have greater resistance not sutiable for most battery projects.

100% pure nickel strip verify all our strips to assure that you are getting thr high quality pure nickel.It also solder incredibly quickly,So you can weld them onto your existing busbar connections to raise the supply of current you can pull through the busbars.The benifits are nearly limitless.

Benefits:

1.Up to 50% lighter than an equivalent deign.

2.Best in class mass energy density at more than160 watt hours per kilograms an extemely efficient design for OEMs and Tier 1 battery pack manufactures.

3.Accomodates all battery cells types and is designed particularly for battery vehicles with larger power packs such as pick up trucks,sport utility vehicles and crossovers.

4.Most cost efficient aluminium solution for mass production electric vehicles when compared to aluminum extrusing and casting intense designs.

5.Low price premimum On $/kg saved compared to equivalent steel designs at substantially lower weight.

The above figure is the typical battery enclosure

As we know

Power = Voltage * Current

3.3*2.5=8.25Kw

To get 18Kwh We are assuming 48s and 44 p

48*48 =2304 cells

Series connections give 48*3.3=158.4V

parallel connections gives 48*2.5=120A

From this we get

158.4*120 = 19.006 Kwh energy capacity

We design battery pack for 48 S and 48p cell along with batteryy spacers to hold cells and for their connections nickel strip is used

When cells are connected by the nickel strip spot welding should be used so that cell does not damage.