How to Repair Cellphone Charging Problems: Not Charging, No Response, or Charger Not Supported
Cellphones can experience several types of charging issues. The most common ones are:
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Not Charging
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No Charging Response
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Charger Not Supported
Understanding the causes behind these issues is key to effectively repairing mobile phones.
1. Not Charging
When you plug in a charger, and the phone shows “Not Charging”, it usually means the required current or voltage is insufficient to charge the battery.
Common cause:
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Faulty BSI line (Battery Size Indicator) – this line informs the charging control circuit about the battery’s specifications and status.
How it works:
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The battery has a BSI output terminal connected to its negative terminal via a resistor.
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If this resistor is damaged or the BSI line is broken, the phone may not recognize the battery correctly, leading to a “Not Charging” message.
Troubleshooting:
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Inspect the BSI line for continuity.
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Check the resistor values and replace if damaged.
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Ensure there is no corrosion on the battery connectors.
2. No Charging Response
If you plug in a charger and the phone shows no response (nothing happens), it could indicate a problem in the protection circuit.
Common cause:
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Faulty protection circuit – this prevents voltage from reaching the charging circuit if a fault is detected.
Troubleshooting steps:
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Check the fuse for continuity.
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Inspect inductors/coils in the charging path.
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Test diodes and capacitors for open or short circuits.
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Ensure voltage is reaching the charging IC or control circuit.
A malfunctioning protection circuit will stop the phone from charging entirely.
3. Charger Not Supported
Sometimes a phone displays “Charger Not Supported”, which prevents charging.
Common cause:
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Faulty BTEMP thermistor – the Battery Temperature sensor monitors the battery during charging. If it reports abnormal temperature values, the phone will block charging as a safety measure.
Troubleshooting steps:
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Check the BTEMP thermistor for proper resistance at room temperature.
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Replace the thermistor if it is damaged or out of specification.
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Inspect surrounding circuitry for shorts or damage.
Summary
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Not Charging: Usually caused by a faulty BSI line.
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No Charging Response: Often due to a faulty protection circuit (fuse, coil, diode, IC).
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Charger Not Supported: Usually caused by a defective BTEMP thermistor.
Not Charging: Usually caused by a faulty BSI line.
No Charging Response: Often due to a faulty protection circuit (fuse, coil, diode, IC).
Charger Not Supported: Usually caused by a defective BTEMP thermistor.
Understanding these circuits and their roles allows you to diagnose and repair charging problems efficiently. Once familiar with these concepts, you can start practicing on real mobile phones to troubleshoot specific charging issues.
[Charger/USB Port] │ ▼ [Fuse] ──> [Coil/Inductor] ──> [Diode/Rectifier] │ ▼ [Charging Control IC / PMIC] │ ┌──────┴────────┐ ▼ ▼ [BSI Line] [BTEMP Thermistor] (Battery (Battery Temperature Size Info) Sensor) │ ▼ [Battery] Explanation of the Diagram Components: Charger/USB Port – Entry point for external voltage/current. Fuse – Protects the circuit from overcurrent; if blown, no charging occurs. Coil/Inductor – Filters current and helps with voltage stabilization. Diode/Rectifier – Ensures current flows in the correct direction to the battery. Charging Control IC / PMIC (Power Management IC) – The brain of the charging circuit; manages voltage, current, and protects against faults. BSI Line (Battery Size Indicator) – Sends battery information to the charging IC to regulate charging correctly. BTEMP Thermistor – Monitors battery temperature; prevents charging if the battery is too hot or too cold. Battery – Receives regulated voltage and current from the charging IC to charge safely.
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