Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

AIM:

To prepare a detailed battery pack drawing along with its enclosure.

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

ANR26650M1-B TECHNICAL DATA

APPLICATIONS

Discharging
Max Continuous Discharage: 50 A
Max Pulse Discharge Current >50% SOC (10s): 120 A
Minimum Voltage: 2 Volts
Temperature: -30ºC to 55ºC

Charging
Recommended Standard Charge: 2.5 Amps
Max Charge Rate: 10 Amps
Max Pulse Charge Current <50% SOC (10s): 25 A
Float Voltage: 3.45 Volts
Recommended charge V & Cut-off Current: 3.6 Volts, taper to 125mA
Temperature
(reduce charging current to 250mA when under 0ºC): 0ºC to 55ºC

Mechanical
Diameter: Ø25.96 +/- 0.5 mm (1.0")
Length: 65.15 +/- 0.5 mm (2.6")
Mass: 76 g

Calculation as per assumptions:- 18kWh Battery Pack

calculation for designing an 18kWh battery pack, basically 18kWh is energy require to achieve the vehicle its proper range. It is depending upon the voltage (V) parameter and ampere-hour or capacity (Ah).

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

Basically, the value of the volume of the cell is used to find out the total volume of the battery pack.
- Single Cell Energy (Wh)

= Cell Capacity (Ah) x Cell Voltage (V)

= 2.6 x 3.3

= 8.58 Wh

The value of a single cell is used to calculate the total energy of the battery pack.
-Single Cell Energy Density

Volumetric energy (Wh/m^3) = Single Cell Energy / Volume of each cell

= 8.58 Wh / 0.03451 m^3

= 248.62 Wh/m^3
Gravimetric energy (Wh/kg) = Single Cell Energy / Single Cell Mass

= 8.58 Wh / 0.076 kg

= 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 in 18 kWh battery pack. Also, I assume 145.2 nominal voltage for series connection.
So,
Vehicle Range = 250 KM (assumed)
Battery Pack capacity = 18.121 kWh or 18120.96 Wh (For better and accurate calculation here I change kWh)
Now,
We will calculate per km average energy = 18120.96 / 250
= 72.483 Wh/km

Therefor,
Battery Pack total energy = Average energy x km
= 72.483 x 250
= 18120.96 Wh or 18.120 kwh

Cell Energy is 8.25 Wh

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

Single Cell Energy Density

Volumetric energy (Wh/m³) = Single Cell Energy / Volume of each cell

= 8.25 Wh / 0.0000344929m³

=2,39,179.6572 Wh/m³

Single Cell Energy Density is 2,39,179.6572 Wh/m³

Battery Pack Assumtions:

There are 50 cell are in series and 44 cells are in parallel, and as above maintioned we are going to use Cell: ANR26650M1-B this cells.

Battery pack calculation:

Now we calculated parallel and series combinations so we can now calculate total no of cells required

Total no of cells: Series cells * parallel cells

:50*44

:2200.

Total no of cells required are 2200.

So from series and parallel combination, we can calculate the voltage of battery pack and the current of the battery pack.

Voltage= no of cell in series* nominal voltage.

= 50*3.3

= 165V

The total value of voltage is 165V.

Current=No of parallel cells * cell capacity

= 44*2.5

=110Ah.

The total value of Current is 110Ah

So now we can calculate the how much mount of energy this combination have by product of voltage and current, and check the it will satisfied or not our requirement

Energy= Voltage * Current

= 165 * 110

= 18150WAh

The total value of Energy is 18150WAh.

So our calculation are satisfied requirement what we need.

now we have total no of cells and volume of single cell so we can calculate the total volume required for battery pack

Total volume = no of cells * Volume of single cell

= 2200 * 0.0000344929

=0.07588438m3">m^3

Total volume required for battery pack is 0.07588438m^3

We also have single cell weight from that we can calculate the total weight of battery pack without other mechanical and electrical connections.

Weight = No of cells * weight of single cell.

= 2200 * 0.076

= 167.2kg

Weight of battery pack is 167.2kg

Energy dencity= volume * battery pack energy

= 0.07588438 * 18150

= 1,377.301497kWh/m^3

Energy dencity is 1,377.301497kWh/m^3

Battery pack continuous current (A)

= Cell continuous current x No. of cells connected in parallel

= 26 x 48

= 1248 A

This is the power which is supply continue to the whole battery pack system.

Battery pack continuous power (W)

= Battery pack continuous current x Voltage of series connection

=1248 x145.2

= 18120.96 or 18.120 Kwh

Now we all parameters which we need to construct the battery pack in physically.

The arrangement design of single-cell is shown below:

Assembly of the full battery pack with 50s/ 44P. The arrangement of the pack is as follow:

Then,

2112 cells will have 50S / 44P

Here I arrange the pack such that it will build a proper battery pack.

The detail technical specification of 2112 battery pack is as follow:

• Package: 50S / 44P
• Capacity: 110 Ah
• Voltage: 165 V
• Weight: 167.2kg (Only Cells)
• No of Cells: 2100
• Power: 18150Wh or 18.15 kWh

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 [1]:

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 [Wh/kg] and specific power [W/kg] compared with other types

The voltage level of the battery determines the maximum electrical power which can be delivered continuously. Power P [W] is the product between voltage U [V] and current I [A]:

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 400 V.

In the article EV design – energy consumption we have calculated the average energy consumption for propulsion E_p as being 137.8 Wh/km on WLTC drive cycle. On top of the energy needed for propulsion, the high voltage battery must supply the energy for the vehicle’s auxiliary devices E_aux [Wh/km], like: 12 V electrical system, heating, cooling, etc. Also, we have to consider the efficiency of the powertrain η_p [-] during the conversion from electrical energy to mechanical energy.

For the auxiliary devices energy consumption we are going to use data from [3], which contains the typical power requirements of some common vehicle electrical components (auxiliary loads). The prolonged electrical loads (headlights, multimedia, etc.) and intermittent loads (heater, brake lights, wipers, etc.) use on average 430 W of electrical power. The duration of the WLTC cycle is 1800 s (0.5 h), which gives an energy of 215 Wh for the auxiliary loads. If we divide it to the length of the WLTC driving cycle (23.266 km), we get an average energy consumption for the auxiliary loads E_aux of 9.241 Wh/km.

Even if Wh/km is not really energy but factorised energy, since it’s dived per unit of distance (km), for simplicity, we are going to refer to it as average energy.

An example EV battery system with individual cells in series.

Battery pack architectures

All high voltage battery packs are made up from battery cells arranged in strings and modules. A battery cell can be regarded as the smallest division of the voltage.

Individual battery cells may be grouped in parallel and / or series as modules. Further, battery modules can be connected in parallel and / or series to create a battery pack. Depending on the battery parameters, there may be several levels of modularity.

The total battery pack voltage is determined by the number of cells in series. For example, the total (string) voltage of 6 cells connected in series will be the sum of their individual voltage.

In order to increase the current capability the battery capacity, more strings have to be connected in parallel. For example, 3 strings connected in parallel will triple the capacity and current capability of the battery pack.

The high voltage battery pack of Mitsubishi i-MiEV consists of 22 modules made up from 88 cells connected in series. Each module contains 4 prismatic cells. The voltage of each cell is 3.7 V and the total voltage of the battery pack 330 V.

Another example is the high voltage battery pack of Tesla Model S, which has:

• 74 cells in a parallel group
• 6 groups in series for a module
• 16 modules in series
• 7104 cells in total

Design of cell holder (Bottom and Top)

The main function of a battery holder is to keep cells fixed in place safely and securely also it is used to keep cells in a proper arrangement so that there will be a decrease in mechanical vibration, and have a better thermal runway in between the cell gaps. Most of the cell holder is made up of polypropylene or nylon bodies rated for 80–100 °C.

Design of pack cover

Basically, Pack cover is made up of Aluminium and the reason behind is to keep battery pack for lightweight. The casing/cover thickness is 0.5 mm and the design is as shown below:

A bottom cover is shown to cover below the bottom battery holder.

Design of Lower floor case for battery pack

Basically, the lower case is a part which is fitted in an electric vehicle for the assembly of the battery pack. A lower case is also made up of aluminum and it has top cover and bottom cover to battery pack from dust and environmental pollution.

The design of the lower case is shown

Positive and Negative Clip

A positive and negative clip is used to connect the battery end cap i.e (+) and (-). Design is shown below:

To make the battery pack, you have to connect the many cells together by means of Nickel strips or thick wire. Generally, Nickel strips are widely used for this. In general two types of nickel, strips are available in the market: nickel-plated steel strips and pure nickel strips. I will suggest buying a pure nickel. It is a little bit costlier than nickel-plated steel, but it has much lower resistance. Low resistance means, less heat generation during the charging and discharging, which leads to longer useful battery life.

Nickel strips come with different dimensions and lengths.

BATTERY HOLDER ,SPACER For CELL CYLINDRICAL LI-ION

Nickel Strips

Nickel strip is generally used in battery building. Its due to its efficiency of usage in spot welding and soldering as well its high corrosion resistance over time. It has good properties and excellent resistance to many corrosive environments. The pure nickel will never get rust after it applied to battery packs. It won’t 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 suitable for most battery projects.

100% pure nickel strip. verify all of our strips to assure that you are getting the 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 benefits are nearly limitless!

battery enclosure

Design Benefits
• Up to 50 percent lighter than an equivalent steel design
• Best-in-class mass energy density at more than 160
watt-hours per kilogram, an extremely efficient design
for OEMs and Tier 1 battery pack manufacturers.
• Accommodates all battery cell types and is designed
particularly for battery electric vehicles with larger
power packs such as pick-up trucks, sport utility
vehicles and crossovers.
• Most cost-effective aluminum solution for mass
production electric vehicles when compared to
aluminum extrusion and casting-intense designs.
• Low price premium on $/kg saved compared
to equivalent steel designs at substantially
lower weight.

Result

Hence, hence detailed battery pack of ANR26650M1-B cell have been prepared.