Project 1 Mechanical design of battery pack

Cell: ANR26650M1-B specifications

1. Volume of each cell, V_c [m³]

Vc =π⋅(Dc)24⋅LcVc =π⋅(Dc)24⋅Lc

L_c - battery cell length [m]

D_c - battery cell diameter [m]

V_c = (π * 0.0262 /4)* 0.065 = 0.034510 m³

2. Battery cell energy, E_bc [Wh]

Ec=Cc⋅UcEc=Cc⋅Uc

C_c - battery cell capacity [Ah]

U_c - battery cell voltage [v]

E_c = 2.5*3.3 = 8.25 Wh

3. Battery cell energy density

Volumetric energy density, u_V [Wh/m³]

u_V = 8.25/0.034510 = 108.55 Wh/m³

4. Gravimetric energy density, u_G [Wh/kg]

u_G = 8.25/0.076 = 239.06 Wh/kg

With the above cell parameters and the core requirements for the battery (nominal voltage, average energy consumption and vehicle range), we calculate the main parameters of the high voltage battery.

Assumptions:

Battery energy = 18 kwh

Voltage (to run the vehicle) = 300V

(i) Energy = 18 kWh

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

N = 18000 / (3.3*2.5)

N = 2182

We need a minimum of 2182 cells to get 18 kWh energy, now based on that, we need to decide configuration – series and parallel.

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

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

And we assumed 300 Volts are need to run the vehicle.

The nominal voltage of one cell is 3.3 V

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

Ns = 300 / 3.3

Ns = 90.90 = 91

91 cells are connected in series will generate 300 voltage and the capacity of the whole module will be 2.5 Ah

Now we need to find the number of cells which will be connected in a parallel configuration

total Ah rating of a battery pack = 18000/300=60 Ah

Np (cell in parallel) =60/2.5

Np = 24

Hence we take 24 cells for each parallel row, although it is exceeding the required capacity, that is negligible.

Cell architecture = 91 Series and 24 Parallel = 91S24P

(iii) Battery capacity:

We know parallel configured cell multiplies individual cell capacity so,

Capacity = parallel cell row*individual cell capacity

Capacity = 24 * 2.5

Capacity = 60 Ah

(iv) Current supplied by the battery

We have already calculated battery capacity which is 60 Ah means it is going to supply 60 A current per hour. which can be considered as C-rate.

(v) Range:

Let’s powertrain energy consumption = 100 Wh/km at 70% powertrain efficiency

Range = Capacity / energy consumed per kilometre

Range = 18000 / 100

Range = 180 km

So,our vehicle will be able to cover around 180 km with current parameters.

(vi) Internal Resistance of Battery:

The entire resistance encountered by a current as if it flows through a battery from the negative terminal to the positive terminal is known as internal resistance of battery.

(vii) Battery Dimensions:

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

Length of casing (L) = number of cells at series*(cell diameter (26) + margin at both side of cell (4)) + clearance at side (diameter of edged cell + margin)

`= 91*30 + 60`

`L= 2790 mm`

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

`B= 24*30 + 60`

`B =780m`

Height of casing (H) = 65+35 (Height of cell + margin for wiring ,Cell holders and metal strips)

H = 100 mm

(viii) Weight of battery pack

Cell weight = 76g

Number of the cells = 2182

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

W = 76*2184 + 4.5 = 165.9 + 4.5 = 170.4 kg

Cylindrical battery pack assembly equipment:

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

Detailed images:

Conclusion:

Lithium Ion and Lithium Ion Polymer batteries are a great power source for some applications but they require preventive protection during discharging and charging.