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.

ANS:

AIM: To develop  mechanical design of a battery pack based on the 18kWh energy capacity.

The below image is of Nanophosphate High Power Li-ion cell ANR26650M1-B

A123's 26650 cells are capable of delivering very high power due to its use of patented Nanophosphate  battery technology. Based on lithium iron phosphate chemistry (LiFePO4), the cells are inherently safe over a wide range of temperatures and conditions. Whether the application requires outstanding cycle life or stable float reliability, the A123's 26650 cells are suitable for a wide variety of power, pulse, or stand-by applications.

                               

Nanophosphate battery technology offers stable chemistry, faster charging, consistent output, excellent cycle life and superior cost performance. It provides the foundation for safe systems while meeting the most demanding customer requirements. Multiple layers 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 chemistries.

 

Lithium Ion Cell Benefits:

• Safety: Excellent abuse tolerance and environmentally friendly
• Life: Excellent calendar life, 10X cycle life vs. conventional lithium ion
• Power: Over 2,600 W/kg and 5,800 W/L

 

Cylindrical Cell Primary Applications:

• Commercial truck and bus hybrid electric vehicles (HEVs)
• Grid stabilization energy storage systems
• Stationary battery backup systems
• Portable high power devices

 

COMMERCIAL SLTIONS:-

Government Solutions:

• Directed energy 
• Soldier power
• Military power grids
• Military vehicles

 

Advanced lead acid replacement batteries for:

• Medical devices
• Industrial robotics and material handling equipment
• IT backup
• Datacenter UPS
• Autonomously guided vehicle (AGV's)
• Telecom backup

 

Transportaion Solutions:

• Passenger vehicles
• Commercial vehicles
• Off-highway vehicles

 

Grid Solutions:

• Transmission and Distribution 
• Renewables integration
• Reserve capacity
• Frequency regulation

 

ANR26650M1-B Cylindrical Cell Specifications:

Cell Dimensions (mm)	Ø26 x 65
Cell Capacity (nominal/minimum, Ah)	2.5/2.4
Cell Weight (g)	76
Voltage (nominal, V)	3.3
HPPC 10 Sec Discharge Pulse Power 50% SOC	200 W
Internal Impedance (1kHz AC typical, mΩ)	6
Recommended Fast Charge Method to 80% SOC	4C to 3.6V CC, 12 min
Recommended Standard Charge Method	1C to 3.6V CCCV, 45 min
Maximum Pulse Discharge (10 seconds, A)	120 A
Maximum Continuous Discharge (A)	70
Cycle Life at 10C Discharge, 100% DOD	>1,000 cycles
Storage Temperature	-40°C to 60°C
Operating Temperature	-30°C to 55°C

 

 

                           Constant Power Discharge Characteristics at 23°C             2.5C Constant Current Discharge at Various Temperatures

                          

 

                                                Cycle Life Performance, 100% DOD, Various Temperatures and Discharge Rates

                            

 

 

About CELL:

The LithiumWerks formerly known as A123 System.The ANR26650M1-B is one of the pioneering 26650 cylindrical cells, now with greater energy & power density and lower impedance. This versatile L-ion cell is suitable for a wide variety of system designs and applications . 

 

About MODULE:

A BMS(battery management system) is any electronic system that handles or manages a rechargeable battery (cell or pack). The BMS manages the battery such as by protecting battery from operating it outside safe operating area, calculating secondary data, monitoring its state, controlling its environment, reporting that data.

 

About BATTERY PACK:

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

 

 

MECHANICAL DESIGN OF BATERY PACK:

One of the most important part or a cmponent of a battery electric vehicle is the high voltage battery.  The battery parameters have a significant effect/influence on other vehicle components and attributes, like:

• maximum regeneration brake torque
• maximum traction motor torque
• vehicle total weight
• vehicle price
• vehicle range

Pretty much all major aspects of a battery operated vehicle (EV) depend on the high voltage battery parameters.

For our E-vehicle battery design, we start with the 4 core input parameters:

• chemistry
• vehicle range
• voltage
• average energy consumption of the vehicle on a driving cycle

A battery is made up of one or more electrochemical cells (battery cells) which converts electrical energy into chemical energy (during charging) and chemical energy into electrical energy (during discharging). The chemical reactions during discharging-charging operation and the type of elements contained within a battery define the chemistry of a battery.

A battery cell made up of five major components: electrodes –  cathode and anode, terminals, separators, electrolyte & a case or enclosure.Different types of cells used for automotive applications: 

 

Individual cells  are grouped together into a single electrical and mechanical unit called a battery module. Later these modules are electrically connected to form a battery pack. 

There are several types of batteries (chemistry) used in electric and hybrid vehicle propulsion systems but we'll just focus on Li-ion cells. The main reason of using Lithium-ion batteries is that thay have higher specific power [W/kg] and higher specific energy [Wh/kg] compared with other types. It can be seen from the Ragone plot that Li-ion batteries have batter performance parameters.

 

 

EV DESIGN : (Battery Calculation)

Assumptions:

Battery energy = 18 kwh

Voltage (to run the vehicle) = 400V (between 400V to 800V)

 

Therefore,

(i) Energy/capacity = 18 kWh 

(ii) Number of cells (N) = energy/(capacity*nominal voltage)

                                N = 18000/(2.5*3.3)

                                N`~~` 2182 cells

 

To get 18kWh capacity or energy we need a minimum of 2182 cells. Now based on that, we need to decide pack configuration – parallel and series.

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

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

And we have assumed 400 Volts are needed to run the vehicle.

 

The cell nominal voltage(from daasheet) of a single cell is 3.3V

Number of cells to be connected in series to produce required 400 V (Ns) = pack voltage / nominal voltage of one cell

Ns = 400/3.3

Ns = 121.21`~~`122

 

These 122 cells will be connected in series which will provide 400 voltule capacity will be 2.5 Ah.

Now we need to calculate number of cells which need to be connected in a parallel configuration

Np(cell in parallel) = total cell/No. of series cells(Ns)

Np = 2182/122

Np = 17.8`~~`18

 

Hence we need 18 cells to be connected fo each parallel row, though it is exceeding required capacity, that is negligible or we consider as tolerance.

Therefore the Cell architecture = 122 Series & 18 Parallel = 122S18P

 

(iii) Battery capacity:

We know that the parallel configured cell multiplies the individual cell capacity so,

Capacity = individual cell capacity*parallel cell row

Capacity = 2.5*18 

Capacity = 45 Ah

 

(iv) Current supplied by the battery

As per our calculation, the batery pack capacity is 45Ah which means the pack is going to suply 45 A current for 1 hr if 1C rate is demanded. And according to load demand the battery will supply the power.

 

(v) Range:

Let’s assume that the powertrain energy consumption is 100 Wh/km at 70% powertrain efficiency

Range = Capacity/energy consumed per km

Range = 18000/100

Range = 180 km

So, with the current parameters (calculated/assumed) our vehicle will be able to cover around 180 km distance.

 

(vi) Internal Resistance of Battery:

The entire resistance experienced by a current as if it is flowing through a battery from negative terminal to positive terminal is known as battery internal resistance.

 

(vii) Battery Dimensions:

ANR26650 cell has 65mm height & 26mm diameter. So, by considering these measurements we have to decide battery size of battery casing.

Length of casing (L) = No. of series cells*(cell diameter (26) + margin at both side of cell (4)) + clearance at end side (diameter of edged cell + margin)

L = (122*30) + 2*(26+4)

L = 3660 + 60

Length = 3720 mm

 

Breadth of casing (B) = No. of parallel cells*(cell diameter (26) + margin at both side of cell (4)) + clearance at end side (diameter of edged cell + margin)

B = (18*30) + 2*(26+4)

B = 540 + 60

Breadth = 600 mm

 

Height of casing (H) = (Height of cell + margin for wiring, metal strips & cell holders)

H = 65+35 

Height = 100 mm

 

(viii) Weight of battery pack

Cell weight(datasheet) = 76g

Total No. of cells = 2182

Battery pack weight (W) = (number of cells*cell weight) + weight of accessories

W = (2182*76) + 4.5

W= 165.8 + 4.5

Weight = 170.3 kg

 

Cylindrical battery pack assembly equipment:

Product Name	Description
512 Channel Battery Tester	5V 2A/3A/5A/6A 512 Channel Battery Testser optional
Automatic Cylindrical Battery PVC Heat Shrink Wrapping Machine	Film speed:50~70PCS/MIN Film precision:±0.1MM
Battery Sorting Machine	(5/6/9/11/13/22 Channel Battery Sorter optional) Data record funtion is selectable
Battery Labling Insulation Paper Sticking/Pasting Machine	Sticker Matrials:Barley paper or PVC Barley paper Maxium 350mm;Scroll Internal Diameter 72-75MM
Manual Spot Welding Machine	Pneumatic AC Spot Welding Machine (Single Welding Point or Doubel Welding Point)
Automatic Spot Welding Machine	Double Sides Spot Welding Machine
Manual Spot Welding Machine	DC Output Spot Welding Machine
Manual Spot Welding Machine	AC Pedal Manual Spot Welding Machine
Manual Spot Welding Machine	AC Pulse Pneumatic Spot Welding Machine
Manual Spot Welding Machine	5000A/8000A Pneumatic Inverter DC Spot Welding Machine
1-24 series or 1-32 series BMS Tester	Over-discharge Protection Current:0-120A Overcharge Protection Current:0-50A Overcharge/Overdischarge Voltage:0.5-5V
Aging Machine	30 V 10A Charging 20 A Discharging Aging Machine
Aging Machine	100 V 10A Charging 20 A Discharging Aging Machine
Aging Machine	70 V 5A Charging 10 A Discharging Aging Machine
Battery Comprehensive Tester	100V 120A 18650 Battery Pack Comprehensive Tester

 

 

Detailed Image of Battery Pack Construction:

 

 

 

CONCLUSION:

Lithium Ion polymer & Lithium Ion batteries provides great power source for some of the applications but during charging & discharging operation, they need preventive protections to overcome any hazardous condition.