Record the specs for 3 batteries: chemistry, voltage, and capacity (if capacity is in amp hours, can you get to watt hours?).

Energy(wh)  =  voltage * current * time

1.) iPhone XS Battery :

• Chemistry: lithium ion
• Voltage: 3.8v
• Capacity: 2.658 Ah
• Watt hours: 3.8v * 2.658Ah = 10.1004 Wh

2.) Headphones Battery:

• Chemistry: Li-Polymer
• Voltage: 3.7v
• Capacity: 180mAh
• Watt hours: 3.7 * 0.18A = 0.666 Wh

3.) FitBit Battery:

• Chemistry: Lithium Coin
• Voltage: 3v
• Capacity: 163mAh
• Watt hours: 3 * 0.163A = 0.489 Wh