Batteries

This Repository will explain my 3rd task in Electronics and Electrical power department at SMART METHODS summer training.

Task Requirements:

• Battery types and selecting the best one for suppling the robot, considering the longest working time and costs criteria.
• Calculate the capacity needed for our application (How many mAh needed).
• Design battery charging circuit.

Detailed Steps:

1. Battery types:

   • Lead Acid Battery:

     

   Specification	Calculation
   Volt , Capacity	12v , 7Ah
   power hour	12v*7Ah = 84 Wh
   price (SAR)	98 SAR
   power hour/price	60Wh/50SAR = 0.85 Wh/SAR
   Size	large
   weight	High weight

   • Lithium-ion Battery:

   

   Specification	Calculation
   Volt , Capacity	3.7v , 2400mAh
   power hour	3.7v*2400mAh = 8.88 Wh
   price (SAR)	10 SAR
   power hour/price	8.88Wh/10SAR = 0.88 Wh/SAR
   Size	small
   weight	light weight

   • Lithium-polymer Battery:

   

   Specification	Calculation
   Volt , Capacity	3.7v , 2000mAh
   power hour	3.7v*2000mAh = 7.4 Wh
   price (SAR)	35 SAR
   power hour/price	8.8Wh/10SAR = 0.21 Wh/SAR
   Size	small
   weight	light weight

• Based on the above details and battery specification, the best battery to choose is the Lithium-ion battery because its provide more power and long time compare it with its price.

2. Now, lets select how many Lithium-ion batteries we need for our application which mean what is the capacity (mAh) needed for the battery:

• Assume the motors is 12v, 6 watt DC motor, fistly finding the current in Amp that consumed by the motor to run:

  I=Power/Volt= 6/12= 0.5A (Theoritical).

• Secondlly,finding the power hour

  To run 6 watt in 1 hour, 6watt*1hour= 6 Wh, and for saftey reasons multiply by 1.2 as a safety factor. So, Wh=7.2Wh.

• Finally, to get the capacity of the battery convert Wh to Ah

  P=IV > 7.2Wh=Ah12v > Ah=0.6Ah. So, to run a 6watt-12Volt motor for 1 hour a 600 mAh lithium ion battery is needed.

• If we used L298D driver for the DC motors, from the datasheet the max current can driver provide for one motor is 2A (4A for 2 motors). So, battery capacity will depend on the runing time and if we want to run the motors for 1 hour, the battery capacity needed is > 4A*1h=4Ah and since the driver can work from 2-35v we will provide the driver with 12v as a power supply. =============================================================================

3. To get 12 Volt connect 4 lithium ion battery in series

   • 12V, 2400mAh Lithium ion Battery

   

4. Now, lets design the battery charging circuit:

5. Task is Done 😍