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.

AIM:

To Prepare a detailed battery pack drawing along with its enclosure with ANR26650M1-B by a capacity of 18 kWh.

ANR26650M1-B is a Nano phosphate high power lithium-ion cell which is made by lithium iron phosphate (LiFePo4). This is more power and have high energy than other cells and lower impedance it has high efficiency with more safety precautions also having long life. It has wide range of SOC with less losses which leads to less discharge for long range with lighter weight. These cells have low-capacity loss and impedance growth over time as well as high usable energy over wide state of charge range.

It is widely used in all areas which have necessity of high power and energy as, transmission and distribution, grids, power plants, EV and HEV vehicles, military machines and vehicles. And it uses also in system back-ups, industrial robotics, medical devices etc.

The view of the ANR26650M1-B is as shown below, by the A123 systems manufacturer.

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.

If we observe the characteristics of the ANR26650M1-B by different conditions like constant power discharge characteristics, constant current discharge at various temperatures, and some other as shown below,

If we observe here that by changing the power that is by increasing the power at constant temperature it decreases the voltage respectively.

If we observe here by changing the temperature from 45 degrees to – 15 degrees it reduce respectively as shown above.

In this as we can see that by changing the charging and discharging cases as shown its performance characteristics changed her (+) represents charging and (-) represents discharging. By changing the temperatures its performance change.

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

Solution:-

Fig. Battery Pack and its parts.

Building steps of the battery pack:

Parts of the battery

The main parts of the battery system are, cells, modules, BMS, wires, strips, case, separators, insulators, sensors etc.\

The complete manufacturing processes of the battery pack look like as shown.

These are the equipment’s that is used to complete the total battery pack through the machines.

The machines that we used for the battery packing are,

• Auto sticker machine, auto sorting machine, spot welding machine, shrinking machine, code printing machine, and aging machine.
• Auto sticker machine is used to stickering the names that is labelling to the cells based on the given values its condition and some other parameters basses.
• The sorting machine can execute the sorting test based on the voltage and internal resistance tests before assembly. the battery sorter machine has 8 channels for OK battery cells and 1 for NG battery cells, which greatly promote the sorting efficiency and ensure the normalization of cells sorting.
• To build the battery pack the cell parameters its working and mechanical design are very important. The battery calculations are used to build the pack with specific idea based on our requirement. By this we can find the exact size, its location, necessary of the cooling system etc can be find.

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

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

Fig. Cells in series arrangment

Now calculate cell required for parallel combination:

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

Parallel combination = total capacity / nominal capacity

Parallel combination =150/2.5

Fig. Cells in Parallel Arrangment

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

The total cell model is having the pack of 37S60P configuration

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

calculatingVolume 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

Battery module:

The total battery power = (60*3.3 V) * (37*2.5 Ah)

= 18315 Wh

= 18.315 kWh

To build such a large grid, we need to slip the battery packs into the battery module, which reduce the complexity of monitoring and optimising battery management and minimizing battery damage.

For that we use the modules which take care of cells protection, monitoring, connections of set of the cells.

In this we are dividing the set of cells from battery pack 37S60P into 5S4P.

So, the no of cells in each module are = 5*4

=20

Total no of cells = 2220 cells

Therefore, no of modules = 2220 / 20

= 111 modules.

let assume the vehicle range is 140 km

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

So, the energy consumption for 1 km is 129 Wh. So, the total range of the battery for 18kWh is 180 Km.

There fore the no of kilometres that a vehicle run with full charge of 18kWh is 140Km.

Battery enclosure pack size:

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

Length of casing (L) = number of cells at series*(cell diameter (26) + margin at both side of the cell which to free up space called holders and gaps for the sheet protectors etc (4) + clearance at side (diameter of edged cell + margin) (All should be in value with mm)

L = 37*30+80

L = 1190 mm.

Breadth of casing (B) = number of cells at parallel*(cell diameter (26) + margin at both side of the cell (4) + clearance at side (diameter of edged cell + margin) for protection

B = 60*30 + 80

B = 1880 mm

There fore the total area of the battery is =Length of casing X Breadth of casing

=1190 mm X 1880 mm

=1.19 m X 1.18 m

= 1.40 m^2.

The Battery Management System (BMS) is connected to the cells modules and battery which is used to identify the critical situations like the voltage, temperature, battery capacity values at the running of the battery time. It is mainly used for the monitoring purpose and balancing of the cells in the battery pack. By this we can operate with out and damages which leads to explode at critical situations.

shrinking machine is used to shrink the battery pack with certain heated temperature in the form of air in the closed loop. The code printing and the aging machine are used to print he code value of the battery cell like ANR26650M1-B and life time of the battery be calculated respectively.

The testers are used to confirm the cell total parameters like voltage, capacity, temperature, pressure, BMS, chemicals etc.