CMT CMT Battery & Power Management 3

Question 1

A customer's phone consistently shows 20% battery remaining but then suddenly shuts off. What is the most likely cause?

Accepted Answer

Battery capacity degradation causing inaccurate state-of-charge readings

Answer

Operating system crash due to software corruption

Answer

Faulty charging port preventing proper voltage sensing

Answer

Cellular radio interference with the battery management IC

Question 2

What is the typical lifespan of a Li-Ion smartphone battery measured in charge cycles before it degrades to approximately 80% of original capacity?

Accepted Answer

300–500 cycles

Answer

50–100 cycles

Answer

1,000–2,000 cycles

Answer

5,000+ cycles

Question 3

Which factor most accelerates Li-Ion battery degradation over time?

Accepted Answer

Consistently charging to 100% and discharging to 0% combined with high heat exposure

Answer

Frequently using the device while it charges

Answer

Using third-party USB cables with original chargers

Answer

Enabling dark mode on OLED displays

Question 4

What does 'Pass-Through Charging' mean in the context of power banks and mobile devices?

Accepted Answer

Simultaneously charging the power bank while it charges a connected device

Answer

Wirelessly charging a device through a protective case

Answer

Transferring charge from one device battery directly to another

Answer

A fast-charge mode that bypasses the battery and powers the device directly

Question 5

When replacing a soldered-in (non-removable) smartphone battery, what tool is most essential for safely separating the battery from the device chassis?

Accepted Answer

A heat gun or iOpener to soften adhesive securing the battery

Answer

A standard Phillips screwdriver

Answer

An electrostatic discharge (ESD) mat only

Answer

A digital multimeter

Question 6

Which charging behavior is recommended to maximize long-term Li-Ion battery health?

Accepted Answer

Keep battery between 20–80% charge and avoid prolonged exposure to high heat while charging

Answer

Charge only when battery reaches 0% and always charge to 100%

Answer

Charge in short bursts of 5–10 minutes multiple times per day

Answer

Always use the fastest available charger to minimize time at high charge states

Question 7

What is the purpose of the 'constant voltage' (CV) phase in a Li-Ion battery charging cycle?

Accepted Answer

To taper the current as the battery approaches full charge to prevent overcharging

Answer

To rapidly charge the battery from 0% to 50% as quickly as possible

Answer

To test cell integrity by applying a fixed voltage and measuring current draw

Answer

To balance individual cells in a multi-cell battery pack