4A: Battery

Make sure that your CoDrone Mini is paired before starting the lesson! If you forgot how to do this, make sure to review how to pair to Blockly here.

A battery is a device that can hold energy and can deliver electrical power. Batteries come in all shapes and sizes and can output various amounts of power. For example, a battery for a small toy will be much smaller and less powerful than a battery for an electric car.

You are probably most familiar with a AA battery. You use these to power flashlights, toys, household appliances, and even some robots! When you need to power a drone, you need a lighter and more powerful battery to be able to fly into the air.

This is why most drones, including CoDrone Mini, have a lithium polymer battery. These batteries are specially designed to be lightweight and to deliver a lot of electrical energy quickly. These batteries are also inside of phones, tablets, and laptops. This makes the lithium polymer battery the best battery to power high-speed motors for flying!

CoDrone Mini has a function that can return an estimate of the percentage of charge that is remaining. The function will return a value from 0-100, 100 being fully charged and 0 meaning you should plug in your battery! Try printing the battery percentage using the print block connected to the get_battery_percentage() block, which is found in the sensor category.

You can also save the value of the battery percentage in a variable to use it later in your program. Create a variable called “battery” and assign it to the battery percentage. Then, print out the variable value.

Whenever you fly, energy from the battery gets used up to power the motors. To see how much the battery level drops during a takeoff, hover, and land, run the following experiment:

For example, your data might look like this:

84

55

48

51

The biggest drop in battery percentage is right after the takeoff. It drops from 84 to 55. This makes sense because you are accelerating against gravity to take off. The second greatest drop is right after hovering for 3 seconds. 

You will notice that after running this test the battery percentage will go back up to a number close to your starting percentage. The battery level goes up and down during the flight depending on how much energy is being used on that movement.

Practice: Take battery measurements before AND after different flight movements. Try changing the number of seconds you are flying or the power value. Which movements use up the most energy?

Most devices have an LED that will indicate the battery level of your device. For example, some computers may have a red or orange LED that turns on when you have low battery. In this activity, you will change CoDrone Mini’s LED according to the battery level. You will need variables, LED blocks, conditionals, and flight events!

Below is the pseudocode for this project:

• CDM LED initially set to white
• Check battery level and save it to a variable
• Wait 1 second
• If the battery level is greater than 75, turn LED green and takeoff, hover, and land
• Else if the battery level is greater than 50, turn LED yellow and takeoff, hover, and land
• Else if the battery level is greater than 25, turn LED red and takeoff, hover, and land
• Else, show the flashing red LED pattern and do nothing

If you need some help, check out the solution below!