Phone Not Charging? Causes and How a Technician Finds the Fault

A phone that will not charge usually has one of four causes: the cable or charger, the charging port, the battery, or, less often, the charging circuit on the motherboard. Check them in that order. Each check takes less time than the one after it.

Safe checks to do first

• Try a different cable and a different charger, and a different socket.

• Look into the charging port with a light. Pocket lint packs into the port and stops the plug from seating.

• If there is lint, switch the phone off and clean the port gently with a wooden or plastic pick. Never use a metal pin: it can short or bend the contacts.

• Restart the phone, and check that the charging cable is fully inserted.

• Check the battery: has it become very short-lived, or is the phone old?

The common causes and what each one looks like

A faulty cable or charger

Charging starts and stops when the cable moves, or the phone charges very slowly. Cables wear out where they bend, and low-quality chargers often deliver less power than they claim. Swapping in a cable and charger you trust settles this in a minute.

A dirty or damaged charging port

The plug feels loose, charges only at an angle, or does not click in as it used to. If cleaning does not help, the port itself is worn or bent and needs replacing.

A worn-out battery

The phone charges but loses charge fast, shuts down at a high percentage, or does not start at all. Batteries age with use, and a replacement battery restores normal behaviour.

A swollen battery

If the back cover lifts or the screen pushes up, the battery is swelling. Stop charging the phone, do not press on or puncture the battery, and have it replaced by a technician.

The charging flex or sub-board

On many phones the charging port sits on a small flex cable or sub-board. If that part is damaged or has been exposed to liquid, the phone may charge intermittently or not at all, and replacing the flex or sub-board repairs it.

The charging circuit on the motherboard

The cable, charger, port and battery are all good, and the phone still will not charge. The fault is on the board: the power or charging IC, the USB circuit or a failed component around them. This is a board-level repair, done with a multimeter, a soldering iron and a hot-air station.

How a technician tests the charging path

1. Test with a known-good cable and charger.

2. Inspect the port and the charging flex for damage, lint, corrosion and liquid marks.

3. Measure the battery voltage, and the voltage arriving at the charging connector.

4. Look for a short circuit on the charging line.

5. If the port and flex are good, trace the charging circuit on the board and test the components around the charging and power ICs.

Where technicians learn this

Charging faults are among the most common phone repairs. In IMT Computers' Mobile Phone Technician course, week 6 covers the phone power and charging system, from battery power flow and the charging circuit to no-charging and slow-charging diagnosis and charging port replacement. Soldering and board-level repair follow in week 8. For the bigger picture, read how to become a phone repair technician in Nigeria.

Frequently Asked Questions

Why does my phone charge very slowly?

Common causes are a worn cable, a low-power charger, a dirty port and an ageing battery. Try a different cable and charger first, then clean the port.

Is it safe to clean the charging port?

Yes, if you switch the phone off and use a wooden or plastic pick, gently. Do not use metal, and do not use liquids.

Can a water-damaged phone be repaired?

Often, if the board is cleaned and the corroded parts are replaced, but the sooner a technician opens it the better. Switch the phone off, do not charge it, and take it to a technician.

Want to learn to repair phones? See the Mobile Phone Technician course or compare all four repair courses on Laptop & Phone Repair Training.