Power Management in Devices – JSS2 Computer Hardware & GSM Repair Lesson Note (Third Term)

Power management is the smart use of a device’s settings and habits so that its battery lasts as long as possible before the next charge.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define a battery and power management.
2. Name the three main things that drain a phone battery.
3. Apply simple settings to save battery power.
4. State habits that keep a battery healthy for years.
5. Explain what Power Saving Mode does and describe the Sleep, Hibernate and Shut down options on a laptop.

What is power management?

Power management means controlling how much energy a device uses from its battery.

• Battery: a part that stores electrical energy and supplies it to a phone, tablet or laptop.
• Charger: a device that sends electricity into the battery to refill it.
• Battery percentage: a number on the screen that shows how much charge is left.
• Race idea: sprinting makes a runner tire quickly, while steady jogging goes further. A device that uses less power lasts longer in the same way.

What are the main battery killers?

Three things use up the most power on a phone: the screen, wireless signals and background apps.

• The screen: usually the biggest user of power. The brighter it is, the more energy it uses.
• Radios (wireless signals): Wi-Fi, Bluetooth and GPS (Maps) keep searching for signals, which uses energy.
• Background apps: apps such as Facebook, WhatsApp and games keep working quietly, checking for messages or updates.

How can you save battery power?

You can save battery by changing a few simple settings and habits.

1. Dim the lights: turn down the brightness. Auto-Brightness adjusts the light to suit the room.
2. Use a short screen timeout: set the screen to switch off after a short idle time, for example 30 seconds.
3. Use Airplane Mode in weak network areas: in a place with poor signal, the phone works harder to find a connection and uses more power. Airplane Mode stops this search.
4. Close unused apps: a game opened hours ago may still be using power. Use the Recent Apps button to swipe away finished apps.
5. Turn off Wi-Fi and Bluetooth: switch them off when you are not using them.

How do you keep a battery healthy for years?

Battery health is how well a battery still holds charge after months of use, and good habits slow its wear.

• Avoid extreme heat: heat is one of the biggest enemies of batteries. Never leave a phone on a hot car dashboard or under a pillow while charging.
• Do not always charge to 100%: many modern batteries last longer when kept between about 20% and 80%. Charging to 100% every time can wear them out faster.
• Use original chargers: cheap fake chargers can send too much or too little electricity, which damages the inside of the battery.

What is Power Saving Mode?

Power Saving Mode, also called Low Power Mode or Battery Saver, is a built-in setting that reduces power use to make the battery last longer.

• Android: usually called Power Saving Mode or Battery Saver.
• iOS (iPhone): called Low Power Mode.
• Windows: called Battery Saver on laptops.

What happens when Power Saving Mode is on?

• The screen becomes slightly dimmer.
• The phone checks for emails and updates less often.
• The CPU (the “brain” of the device) slows down a little to save energy.
• Vibrations for notifications are turned off.

What are the power options on a laptop?

A laptop has three main ways to stop using full power when you finish working: Sleep, Hibernate and Shut down.

• Sleep: the laptop uses very little power and keeps your open work in memory, so it wakes quickly.
• Hibernate: the laptop saves your open work to the hard disk and switches off, so it uses almost no power.
• Shut down: the laptop closes all programs and switches off completely.

What is the power saver’s guide?

The table below shows each feature and the action that saves power.

Teacher’s note

• Practical: show students how to find the Battery Percentage and the Battery Usage graph in the settings of a smartphone.
• Purpose: this lets them see which app uses the most power on their own device.

Evaluation

1. Why does a phone use more battery in a place with a very weak network signal?
2. Mention two things that happen to a phone in Low Power Mode.
3. True or False: it is good for your battery to keep your phone under your pillow while charging at night. Explain your answer.
4. If your phone is at 5% and you need it for an emergency call, what are the first three things you should turn off?
5. State one difference between Sleep and Hibernate on a laptop.

Assignment

Write a short list of five rules for a younger student on how to make a phone battery last longer in one day and stay healthy for years. Give a reason for each rule.