Project 1

Let us concider the cells with

Nominal voltage = 3.6v

Capacity = 3000mAh = 3Ah

First convert the battery capacity 150Kw to Ah

Amper hour = Watt hour / Voltage

Amper hour = 150*1000 / 120 = 1,250 Ah

Series:

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

Number of cells in series = 120/3.6 = 33.33

We have to round off to lower value and higher value

Case-1) Number of cells in series = 33

Case-2) Number of cells in series = 34

Number of cells in series	total voltage	Requred voltage
Case - 1	33	33*3.6 = 118.8	120
Case - 2	34	34*3.6 = 122.4	120

The condition to choose the number of cells are

Nomial voltage of battery should not excide the Load volatge

Max Volatge of battery should be less than the Load Max Volatge

Min Volatge of battery should be greater than the Load min Voltage

We have to round off to lower value so that it will not excide the required value

There fore Number of cells in series = 33

Output total volatge will be 118.8V

The output voltage can be adjusted to 120v by a Buckboost converter to meet the requirment of 120v

Parallel:

Number of cells in parallel = required capacity / cell capacity

Number of cells in parallel = 1,250 / 3 = 416.6

We have to round off to lower value and higher value

Case-1) Round off to lower value = Number of cells in series = 416

Case-2) Round off to higher value Number of cells in series = 417

The output capacity = cell capacity * number of cells in parallel

	Number of cells in Parallel	total Capacity(Ah)	Requred voltage
Case - 1	416	416*3 = 1,248	1250
Case - 2	417	417*3 = 1,251	1250

We can round off to higher value = 417

The output capacity = each cell capacity * number of cells in parallel = 417*3 = 1,251Ah

The number of cells in Parallel = 417

The Output Capacity will be 1,251Ah

The Current can be limitted to requied value bu using current limitters.

Now the battery pack is made of 33S417P pack so that it can meet the required output of 120v,1250Ah or 120V 5Kw

As the number of cells in series and parallel are very high which makes manufacturing difficult. So, we need to divide it into sub battery packs and remake the connections to get the requried output

As the BMS Supports the max 18 cells in series so we need to divide the 33 sereis cells to 18 cells series sub battery pack which leads to 2 seres sub connections one with 18 and another with 15

To make it compact parallel connectons we need to make 52 cells in parallel for each sub pack which leads to 8 parallel connections

Total result in 2 sub battery packs in sereis one with 18 cells in series and another with 15 cells in series and 8 sub battery pack in parallel each with 52 cells in parallel and any one with 53 to meet the requirment 33S417P.

One sub battery pack configuration is 18S52P and another sub battery pack configuration is 15S52P which results in 33S52P pack with 8 copies. these 8 33S52P are connected in parallel (One of the pack with 33S53P) to make 33S417P.

It consisting of input sensors of volatge,current and temperature. The voltage sensor analog signal is converted to digital signal by AFE, the current sennsor analog signal is converted to digital signal by the MCU or we can connect the ADC converter between the Current sensor and MCU, the temperature sensor analog signal is converted to digital signal by the MCU or we can connect the ADC converter between the Temperature sensor and MCU. The Realy module control the Realy which make or brack the circuit by the command given be the MCU. The CAN and RS485 are Communication protocalls to the Outside world.

The Blocks inside the red line are the BMS blocks. It isdesigned with the three 18 cell Slave controller which is AFE, it converts the anolog signal from voltage sensor in the battery to Digital signal. The 3 Slaves are connectes in seres as shown, the salve-1 will collect the data feom module-1 and send to slave-2, slave -2 will collect the data from module-2 , now the salve -2 consisting the data of slave-1 and 2 and it sends the both the data to slave-3, the save-3 will collect the data from module-3, now the slave-3 consisting the data of slave-1,2 and 3, like continues for all 16 slaves and at last all the data is send to Master controller which is MCU. It control the battery pack according to the protocals which is given to MCU.

Note that all the slave have a capacity of 18 cell series connection even though half of the sub battery packs have only 15 series cell besuse if we want to upgrade the capacity we can do by increasing Ah of battery pack i.e., by incresing the number of series cells. It makes easy to upgrade the battery pack but in a limitted way.

We can also use the combination of 8 Master and slave BMS i.e., 2 slaves 18S52Pa and 15S52P and a master controller of 8 numbers. For all master control will have one single controller or all the 8 master controllers can directly connected to the MCU. But its costly and complicated process.