Project 1 Mechanical design of battery pack

Battery pack capacity : 18kWh

Cell : ANR26650M1-B

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

Aim : TO develop a mechanical desgin of battery pack based on the required energy capacity

Nanophosphate High Power Lithium Ion cell ANR26650M1-B :

A123's high-performance Nanophosphate lithium iron phosphate battery technology deleivers high power and energy density combined with excellen safety performance and extensive life cycling in alighter weight, more compact package. cells have low capacity and loss and impedance grwoth over time as well as high usable energy over a wide state of charge eallowing system to meet end of life power and energy requirements with minimal pack oversizing

Applications :

• Datacenter UPS
• Telecom backup
• IT backup
• Autonomously guided vehicle
• industrial robotics and material holding equipment
• Medical devices
• military vechicles
• soldier power
• directed energy

ANR26650M1-B Techincal data :

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 Lithium werks ANR26650M1-B is the next genration of A123 systems pioneering 26650 cylindrical cell,. Based on the Lithium iron phophate chemistry the cells are inherently safe over a wide range of temperatures and conditions FOr outstanding cycle life stable float reliability this cells are suitable for a wide variety of power pulse and stand by applications. Nanophosphate battery technology offers thermal stabel chemistry, fast charging, consistent output, low capacity loss over time

it provides extremly safe conditins for while meeting most demanding customers requirements. Multiple layers of protection are employed on chemistry, cell and system

level to achieve an energy storage solution with superior safety

Dimensions :

Construction of Battery pack :

TO construct a battery pack initially we have to estimate the voltage requirement of the overall load of vehicle.

we had assumed as 400V as mentioned above

then the battery modules should be created in sucha a way that the overall voltage is matched with the load requirement voltage. the modules can be created in series or parallel connections of individual cells. then every modules should be connected in series to consturct teh final battery pack

In series connection - Voltage added and current remains same

In parallel connection - Voltage remains same and current gets added

Here in our case sigle module to produce 400V for our load requirement so to obtain 400V output cells are connected in sereiswhere voltage become added and current remains same. To obtain 400V no of cells required is approximately (400/3.3 =122 cells).

Thus single module gives as 400V from 122 cells bit energy of one module is not enough to run the vehicle as motor power rating is higher. The energy generated from single module is (122*8.25Wh = 1006.5Wh)

So to construct a battery pacl with 18KWh with not exceeding 400V the modules are connected in parallel. In this parallel connections the currents are getting added and voltage remains same as 400V. as current increases the power of the battery pack increases to run the motor load of high power rating. THis can be calculated as (18KWh/1006.5Wh = 17.88), which gives as nearly 18 similar modules should be connected in parallel to acheive 18KWh battery pack

thus the batteyr model is said to e 122S18P configuratuon which gives 2196 cells. from this we have created overall capacity of battery pack as (2196*8.25Wh=18117Wh) which is slightly higher than 18Kwh

The overall capacity of battery pack is given as (2.5Ah*18 =45Ah).

Which means it is provided 45A of currrent continously for one hour to full discharge thus 18 modules should be arranged in a way as battery pack to fit in EV chasis

Enclousure construction :

To find the overall enclousure volume we have to find the volume of single module volume consists of 122cells in series connection and multiplied with 18 parallel connected module volume

SIngle module

Let as assume 122 cells(single module) are divided into 2 modules of 61+61 cells.

The length of the module=No.of cell in row*(Cell dia + Margin at both side of cells) + clearance at side(2(cell dia + margin)).

=61*(26+4) +60 =1890mm.

The bredth of the module=(cell dia +Margin of both side of cells + clearance)

=26+4+60 =90mm.

Height of the module=Height of cell + connectiing strip thickness,wires say 35mm

=65+35 =100 mm.

Thus the volume required for single module is 1.8*0.09*0.1 = 0.0162 m3.

thus the volume required for single module is 1.8*0.09*0.1 = 0.0162m3

Therefore the volume (total) required for battery pack of 122S18P configuration construction is 0.0162*36 = 0.583m3

THus from the above results it is assumed approximately 1m3 of volume should be used for EV battery pack with additional ventilation spaces for pack

We can assume that two modules are combined into one cabonet so 18 cabinets should be connected to form final battery pack

MAterials and processs in battery pack construction :

Battery pack constructions consists of three mahor levels of processings namely cell level module level, pack level constructions. The electrodes are combined with electroyte to various cell models as cylindrical, prismatic pouch type cells.

After case sealing cells are combined to form module level construction. FInally these modules are comined to form pack level constructions

Joining technologies of cells :

the interconnections between cells are practised by various welding techniques some of them are

• Ultrasonic metal welding
• resistance welding
• laser beam welding
• wire bonding
• Mechanical joining

Enclosures

Cells in series connection :

When you connect cells toghetherin sereis it doesnt cahnge the amps or the capacity it only raises the voltage of the pack. Hooking them up in seires means that you connect the postive end of one cel to the negative end of the other

cells in Parallel connections :

If you take several cells and connect their same type electrodes in parallel they all will act as though they are one large cell. alos when you first connect them to each other they must be at the same level of charge.

Cell houlders :

These houldeers are used for houlding the individal cells in a better posture without mis-assemble. the connections can be made accordingly to make series connections and parallel connections to form the required module dimensions.

Battery cabinet arrangements :

Each module are interconnected in series or parallel according to the requirement and packed as a single large cabinet pack as shown

Vent holes are present with enclousre for cooling or heating the battery pack temperature according to its environment conditions. Different cell types are used by different manufacturers of EV such as cylindricla, prismatic, pouch types.

the pack constructions are different for every manufactures.