CMT CMT Battery & Power Management 2 — Questions and Answers
Question 1: What is the recommended storage charge level for a Li-Ion battery if a device will not be used for an extended period?
- 100% (fully charged)
- 0% (fully discharged)
- Approximately 40–60% (Correct answer)
- Exactly 75%
Correct answer: Approximately 40–60%
Storing a Li-Ion battery at approximately 40–60% charge minimizes stress on the cells and slows capacity degradation during long-term storage.
Question 2: Which USB Power Delivery (USB-PD) feature allows a device to act as both a charger and a chargeable device?
- Dual-Role Power (DRP) (Correct answer)
- Battery Charge Specification 1.2
- Voltage Regulator Mode
- Passive Power Switching
Correct answer: Dual-Role Power (DRP)
Dual-Role Power (DRP) in USB Power Delivery allows a port to dynamically switch between acting as a power source and a power sink depending on what is connected.
Question 3: What unit is used to measure the rate of charge or discharge of a battery relative to its capacity?
- Watt-hour (Wh)
- C-rate (Correct answer)
- Ampere (A)
- Coulomb (C)
Correct answer: C-rate
The C-rate expresses charging or discharging current relative to battery capacity; a 1C rate means the battery charges or discharges completely in one hour.
Question 4: What does the Battery Management System (BMS) in a smartphone primarily control?
- CPU power states and thermal throttling only
- Screen brightness based on ambient light
- Charging voltage, current, temperature, and cell balancing to protect battery health (Correct answer)
- Wireless radio power output levels
Correct answer: Charging voltage, current, temperature, and cell balancing to protect battery health
The BMS monitors and controls charging parameters, temperature, state of charge, and cell balancing to protect the battery from damage and extend its lifespan.
Question 5: Wireless charging in smartphones most commonly uses which technology standard?
- Bluetooth Low Energy (BLE) power transfer
- Qi (pronounced 'chee') inductive charging (Correct answer)
- Near Field Communication (NFC) charging
- Radio Frequency Identification (RFID) power harvesting
Correct answer: Qi (pronounced 'chee') inductive charging
Qi is the most widely adopted wireless charging standard for smartphones, using inductive coils to transfer energy between a charging pad and the device.
Question 6: Which setting on a smartphone most significantly reduces battery drain during periods of inactivity?
- Disabling auto-rotate
- Enabling Airplane Mode when not in use (Correct answer)
- Turning off autocorrect
- Disabling screenshot shortcuts
Correct answer: Enabling Airplane Mode when not in use
Airplane Mode disables all radios (cellular, Wi-Fi, Bluetooth, GPS), which are among the largest power consumers, dramatically reducing battery drain.
Question 7: What is 'trickle charging' in the context of mobile battery management?
- Charging at maximum current until 100% is reached
- A slow, low-current charge applied to maintain a fully charged battery or recover a deeply discharged cell (Correct answer)
- A fast-charge protocol that alternates between high and low current
- Charging multiple devices simultaneously at reduced speed
Correct answer: A slow, low-current charge applied to maintain a fully charged battery or recover a deeply discharged cell
Trickle charging delivers a small, continuous current to maintain full charge without overcharging, and can safely recover batteries that have been deeply discharged.
CMT CMT Battery & Power Management 2
What is the recommended storage charge level for a Li-Ion battery if a device will not be used for an extended period?