The battery is used in applications where energy is required to be stored for future purposes. Portable, emergency, and low-power devices generally use batteries. A portable device, such as a mobile laptop, has a battery to use anywhere you want. An emergency device like an inverter, torch, etc., is used when there is no electricity. Low power devices like watches, oximeter, etc., can run for a long time after replacing the battery. The mains supply is not suitable for all situations.

The requirement of a battery depends upon various conditions like how much power is needed or what device portability is. But what about the wall watch? Why is this not connected to a socket?

The wall watch consumes very little power. A 1.2v battery can make it run almost for two years, but this is not the main reason. The watch should be powered up every instant to get the correct time; this can be done by battery. A single hindrance in power will cause a delay in time. That’s why it is designed to work with less power thereby allowing the watch to run for a longer period and making the battery an efficient way to supply power constantly.

Let’s take another example. Generally, a vehicle works on petrol. In a self-start vehicle, the initial ignition of the engine is done by an ignition coil and a motor. The motor is used to reach specific rpm of the engine, and the ignition coil is used as a source of ignition. This vehicle ignition coil draws about four Amps. This current can vary among different manufacturers, and there is lots of space in the vehicle. That’s why to fill the higher current requirement lead-acid battery is perfect for it.