Project 4

For a vehicle of gross weight 300 kg, the motor ratings are 1200Wh, 65V. The range is 225km and the maximum speed is 60kmph. Calculate the capacity of the battery pack required and the number of series-parallel connections. Give a stepwise discussion on how a battery pack is built.
Note: Choose any relevant lithium ion datasheet.

Solution:

here, we know that

vehicle of gross weight = 300kg;

motor ratings = 1200Wh,65V; i = ?;

Range = 225km maximum speed = 60Kmph;

here, first step we shoud calculate the motor current based on the given ratings;

we know that

Power = V*i

1200 = 65*i

i = 1200/65 = 18.46 amperes;

here, we assure current loss in between 1-10%;

Losses in motor current = 18.46

(i) = 18.46*1.25 = 23.07 amp

here we have to calculate the power required based on the given speed which is at 60Kmph

WKT

Power = V*i = 65*23.07 = 1499.55w

after we have to calculate the Travel Factor also

the formula for Travel Factor is

= Total Range/Total Speed

= 225/60 = 3.75

so we have to calculate the power required based on the Travel Factor then,

the Formula is power = Power*Travel Factor = 1499.55*3.75 = 5623.31 = 5.3Kw

After that we have to calculate the Battery Pack

let us consider the Battery pack efficiency = 90-95%

so we required battery pack capacity is = power required/efficiency = 5.3/0.90 = 5.88 Kw

then we have to calculate the Battery Pack efficiency i.e based on the efficiency is

Total Battery pack capacity is = 5.88/0.90 = 6.53 Kwh

after calculating the Battery pack capacity we need to calculate the how much need to find connections of series and parallel

so series connection

motor voltage = 65V

cell voltage = 3.75v

then, no of series cells = motor voltage/cell voltage = 65/3.75 = 17

17 cells in series

parallel connection

Motor Current is 23.07A

cell current is 2.6A

no of parallel cells = Motor current/cell current = 23.07/2.6 = 8

8 cells in parallel

stepwise discussion on how a battery pack is built.

A)These packs are usually constructed by standing two cells side-by-side, and welding a nickel strip across the terminals, as in the ladder pack. The cells are then bent end to end by bending the nickel connecting strip in a "U" shape. Allow a thickness increase of ½ to 1 mm per junction for this.

Case 1: Ladder, linear, F type, or radial

Case 2: Multi-row cells

Case 3: Face centered "cubic"

Case 4: FCC with alternating long and short rows

Case 5: Fixed channel width optimization

The distance P between the cells of Diameter D in a channel with height T is P = sqrt (2TD-T^2)

Case 6: Packing cells in a tube, 3 cells.

Case 7: Packing cells in a tube, 4 cells.

For a four cell pack in a circular tube

Case 8: Packing cells in a tube, up to 91 cells

Cylindrical batteries in a tube of diameter "D"	Approximate diameter of the circumscribing circle	Scheme
2 Cells	2D	Side by side
3 Cells	2.16D	Triangle
4 Cells	2.414 D	Square
5 Cells	2.70	Pentagon
5 Cells	3D	Square with one inside
6 Cells	3D	Hexagon
7 Cells	3D	Hexagon with one inside
8 Cells	3.305D	Heptagon with one inside
9 Cells	3.62D	Octagon with one inside
10 Cells	4.4D	Pentagon with 5 more cells symmetrically arranged around he outside
10 Cells	3.92D	Nonagon with one inside
11 Cells	4D	Nonagon with two inside
12 Cells	4D	Nonagon with three inside
13 Cells	4.24D	Decagon with three inside
14 Cells	4.4D	Decagon with four inside
15 Cells	4.55D	Undecagon with four inside
16 Cells	4.9D	Dodecagon with four inside
19 Cells	5D	Hexagonal close packed
37 Cells	7D	Hexagonal close packed
61 cells	9D	Hexagonal close packed
91 Cells	11D	Hexagonal close packed

Case 9: Linear, or L-type, or Axial

This is a stack of cells end to end.

Most battery packs are spot welded together using nickel strip for contacts. Soldering directly to the cells is dangerous for the cells.