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.

Here we have to prepare detail of battery pack of having 18 kwh capacity

Here ANR26650M1-B cell is given which is rechargeable cell

So 1^st we download the data sheet of ANR26650M1-B cell

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.

Battery pack:

A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density.

From above datasheet we understand cell specification which is are as follow

ANR26650M1-B Specifications

Nominal Ratings

• Voltage: 3.3 Volts
• Capacity: 2.5 Ah
• Energy: 8.25 Wh
• Specific Power: 2600 W/kg
• Impedance (1KHz AC Typical) 6 mº
• Cycle Life at 1C/1C, 100% DOD: > 4000 cycles
• Cell Type: 26650 Lithium Ion Power Cylindrical Cell

Discharging

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

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 0°C): 0°C to 55°C

Mechanical

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

For design the battery here we have to find mechanical and electrical parameter of cell with the help of above given parameter

Solution:-

Required battery pack capacity=18kwh

here the mentioned cell data

Nominal voltage 3.3V

capacity is 2.5Ah

We assume its 120 V battery pack

So we have to find capacity of battery pack

Capacity in Ah= power/ volt

capacity in Ah=(18*1000)/120

capacity in Ah=150 Ah

Now calculating series and parallel combination of battery pack arrangement

So for series combination = Total voltage / Nominal voltage

For series combination =120/3.3

= 36.36 similar to 37

So for series combination 37 cell required

Now calculate cell required for parallel combination

Parallel combination = total capacity / nominal capacity

Parallel combination =150/2.5

To get the required 150 Ah we need 60 parallel cell series

So calculating total no. of cell required in battery pack

Total no. of cell in pack = No. of cell in series * No. of cell in parallel

Total no. of cell in pack =37*60

Total no. of cell in pack =2220 Nos

For battery pack we have to find area and volume of pack

calculating mass of the battery pack

mass of the battery pack =total no. of cell * each cell mass

=2220*0.076

=168.72 kg

calculating Volume of pack

Volume of pack=total no. of cell * each cell volume

= 2220* 3.14*0.013^2*0.065

= 0.0765742 m^3

calculating Cell peak current

Cell peak current = max. pulse charge current * single cell capacity

=20*2.5

=50 A

calculating Battery pack peak current

Battery pack peak current = total no. of cell in series * each cell peak current

= 37*50

=1850 A

calculating Cell continuous current

Cell continuous current = max. continuous charge current * single cell capacity

= 10*2.5

25 A

calculating Battery pack continuous current

Battery pack continuous current = total no. of cell in parallel * each cell continuous current

= 25*60

= 1500 A

let assume the vehicle range is 140 km

Average energy of vehicle = 18000/140 km= 128.57 take 129 wh/km

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