Project 1

1................

AIM

Our aim is to design a battery pack for a car of 150kw with a voltage of 120v

using the specification provided in a question that nominal-voltage is given to be 3.6v

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To design the battery pack we need cells that are connected in series and parallel to meet the requirements.

 calculation---:

Let us consider the cells with

Nominal voltage = 3.6v

Capacity = 3500mAh = 3.5Ah

convert the battery capacity 150Kw to Ah

by the help of the power formula  which is  ............>P = VI

here the voltage given is 120v

150*1000 = 120*I

I = 150000/120......---------------->1250Ah

 a)Series:

Number of cells in series = required voltage / Nominal voltage of the cell

Number of cells in series = 120/3.6 = 33.33

 now we will round off to lower value and higher value  so that 33 and34 these are going to be the two no on which we will carry on our calculation

two cases we will take 

case1                                                                                   case2                                                    

(no of cells in series will be 33)                                             ( no of cells in series will be 34)

>nominal-vol * 33                                                                 >nominal vol*34

   3.6*33 = 118.8v                                                                       3.6*34 = 122.4v                                 

>max vol *33                                                                       >max vol*34

4.2*33 = 138.6v                                                                      4.2*34 = 142.8v

>min vol*33                                                                         > min vol*34

2.7*33 = 89.1v                                                                         2.7*34= 91.8V

it is better to have more voltage so we will choose the higher value for the no of cells

 here the no of cells in a series is 34

the output voltage is about 122v

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Parallel:

Number of cells in parallel = current capacity/cell nominal capacity

The number of cells in parallel = 1,250 / 3 .5 = 357.14

round off to lower value and higher value so that 357and358 these are going to be the two no on which we will carry on our calculation

two cases we will take 

case1                                                                                   case2                                                    

(no of cells in parallel will be 357)                                             ( no of cells in parallel will be 358)

>battery capacity* 357                                                          >battery capacity*358

    3.5*357  = 1249 Ah                                                                         3.5*357=1253Ah

So, there are 34 cells in series and 358 cells in parallel

ie, the battery pack configuration is 34S 358P.

 BMS topology :

As there are about 34 cells in series in the battery pack, we have to use Master-Slave topology as the BMS topology in which Master/slave is a model of communication for hardware devices where one device has unidirectional control over one or more devices. This is often used in the electronic hardware space where one device acts as the controller, whereas the other devices are the ones being controlled.

The total battery pack is made of sub-battery packs so controlling and manufacturing will be easy.

as we have 34 no of cells in series  so we would be requiring two slaves each slave having 18 cells