Lesson 16 40 mins

BATTERIES (5 mins) 

Introduce what a battery is.

Batteries are devices that provide electricity by means of electrochemical cells inside them. Batteries are today utilized in every field, ranging from military to civil, industrial to agricultural, cars to drones. 

TYPES OF BATTERIES (10 mins) 

Explain different types of batteries with their applications..

Batteries are of different types, made with different variety of materials. Some of these batteries are not rechargeable, such as alkaline batteries and some are rechargeable such as Li-ion, Ni-Cd, LiPo, Ni-MH, lead acid. 

Wet cell batteries: 

A wet cell battery generates power from an electrode and a liquid electrolyte solution. Eg. Lead Acid batteries, Ni-Cd batteries, etc. 

Dry cell batteries: 

A dry cell uses a paste electrolyte, with only enough moisture to allow current to flow. Eg. AA, AAA, Li-ion, LiPo, etc. 

Examples: 

Lithium ion Batteries: A lithium-ion battery is a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging. 

Lead acid Batteries: Lead acid batteries are used in automobiles, AA and AAA batteries are used in common appliances. 

For our purpose of providing current for a drone, LiPo batteries are a perfect fit.

WHICH BATTERY SHOULD BE USED ON DRONES? (5 mins) 

Converge the types of batteries and their applications to the battery requirements of a drone. Based on the required qualities, LiPo batteries are the best suited for drones.

The battery used in a drone is a Lithium Polymer or LiPo battery. This battery has various advantages over other traditional batteries. The most important reasons for using LiPo batteries in drones are that they are energy dense and light in weight. The weight of a battery is essentially due to the chemicals inside it which provides electric current. If you compare various types of batteries of equal weight, LiPo batteries provide a very high energy i.e. very high current. Hence, LiPo batteries have an ability to provide more current at very light weight, i.e. they are energy dense. This helps your drone to get high energy without much increase in overall weight. 

PARAMETERS OF LIPO BATTERIES (10 mins) 

Few basic parameters associated with batteries, and their values/range for LiPo batteries.

➔ High Energy Density 

LiPo batteries have a very high energy density i.e. they can carry the maximum amount of energy per unit of weight of the battery. This keeps the battery light and with sufficient energy to power an entire drone + its own weight. 

➔ C-Rating 

Another important factor in a LiPo battery is the C Rating of the battery. C-Rating of a battery refers to the maximum safe discharge current that a battery can provide (without exploding). C-Rating is calculated as: (Max safe current in mA) / (mAh capacity of the battery). Drone motors, especially multi-rotors, generally require a very high current to lift it up. To ensure this, the batteries require to be of a high C-Rating. Many drones use C-Rating between 15C to 25C. 

➔ Voltage 

The operational voltage of a single cell of a LiPo battery is 3.7V. We can get to different values of operational voltages by adding these cells in series and parallel combinations.