Here is a finished 12V 200ampere pack. You can see, it consists of 4 pieces 3.2V 200ampere battery cell, BMS LCD screen and case. 

First, Connect four battery cells in series, and 4 in series can make the voltage reach 12V. 

These cells are brand new and A grade and can cycle up to 5000 times.

Second, fixed the BMS and connect the BMS and battery. 

The full name of BMS is battery management system. It is a device that cooperates with monitoring battery status. The main purpose is to intelligently manage and maintain each battery cell to prevent overcharge and overdischarge of the battery, thereby prolonging the service life of the battery. 

After that, it needs to be tested for voltage capacity by grading system.

After passing the test, put it in the box, this box is made of ABS and PC materials, the box made of these two materials is not only waterproof but also flame retardant.

Finally, connect the LCD screen and close the cover. The battery pack completes a simple 12V 200ampere battery pack assembly.

If you need different voltage and capacity or BMS with bluetooth, it is acceptable to customize according to your needs.