Design of battery pack
AIM: To calculate the capacity of the battery pack required and the number of series-parallel connections.
Requirements: Vehicle gross weight is 300 kg, the motor ratings are 1200Wh, 65V. The range is 225km and the maximum speed is 60kmph.
Given Data
- Vehicle Weight=300kg
- Motor Rating=1200wh.65V
- Range=225Km
- Max Speed=50 kmph
Things need to design battery pack
- Voltage and Ampere hour capacity
Given, operating voltage = 65 V
For Ah,
Given, Wh requirement = 1200 Wh
1200 = 65*I => I = 18.46 Ah
Current Loss has a range of 1-10%
Considering a 10% loss, then required Ah will be 18.46*1.1=20.306 Ah
Power requirement for this Ah is
Power= 65*20.306 = 1320 W
Travel Factor= Total Range/ Total Speed
Travel Factor= Total Range/ Total Speed
Travel Factor = 225/60= 3.75
Power requried = Power*Travel Factor
power requried=1320*3.75=4950 W = 4.95 kw => Capacity required = 4.95 kwh
Battery pack efficiency is 85-95%, considering 85% efficiency
Required Battery Pack Capacity= 4.95/0.85 = 5.82 kwh
Calculating Battery pack efficiency based on motor efficieny
Total Battery Pack capacity = 5.82/0.85 = 6.847 kwh
Power requried = Power*Travel Factor
power requried=1320*3.75=4950 W = 4.95 kw => Capacity required = 4.95 kwh
Battery pack efficiency is 85-95%, considering 85% efficiency
Required Battery Pack Capacity= 4.95/0.85 = 5.82 kwh
Calculating Battery pack efficiency based on motor efficieny
Total Battery Pack capacity = 5.82/0.85 = 6.847 kwh
Required voltage is 65V.
So, required Ah capacity is 6.847*1000/65 = 105.3384 Ah
Consider the cell whose specifications are shown below
Given, nominal voltage of cell =3.6 V
Required voltage = 65 V
No.of cells in series = 65/3.6 = 18.055 = 19 cells
Voltage of pack = 19*3.6 = 68.4 V
Required Ah capacity = 105.3384 Ah
Cell capacity = 3.35 Ah
No.of cells in parallel = 105.3384/3.35 = 31.4443 = 32 cells
Ah capacity of pack=32*3.35= 107.2 Ah
Power delivered by battery pack = 68.4*107.2 = 7.332 kwh
Therefore, required battery configuration is 19S32P, 68.4V, 107.2 Ah