Many customers come in saying, “I’m using a 25W or 45W fast charger, but my phone charges like an old one.”
The truth is: charging speed is a combination of the charger, the cable, the charging port,
the battery health, and even how hot the phone is while charging.

Because we repair phones all day, we can measure real charging power and see what is limiting it.
Quite often, fixing one small issue makes charging two or three times faster again.

The Situation You Already Know Too Well

• You plug in the phone before going out, but after 30 minutes the battery has barely moved.
• You paid extra for a “fast charger” and “PD cable” but notice no real difference.
• Sometimes it shows “fast charging”, sometimes just “charging”, with no clear reason.

This is very common. In most cases, something in the charging chain is limiting the speed,
and your phone is simply protecting itself or doing the best it can with poor power delivery.

Real Cases From Our Repair Benches

• iPhone 12 – Customer used an official fast charger, but power draw was stuck at around 8–10W.
  We found dust and compacted lint inside the Lightning port. After careful cleaning, the phone went back to normal fast charging.
• Galaxy S21 – The “45W” charger they bought online was actually a basic 15W unit with no proper fast-charge protocol.
  With a proper PD/PPS charger and cable, the phone started charging much faster.
• iPhone XR with old battery – Battery health was in the 70% range.
  iOS was limiting charging speed to reduce heat and protect the worn battery.
  After battery replacement, the phone could take higher power safely again.

These are just a few examples. The pattern is the same: the user invests in a fast charger,
but a hidden weak point stops the phone from using its full charging speed.

The Main Reasons Fast Chargers Still Charge Slowly

1. Charger and Phone Use Different Fast-Charging Protocols

Fast charging is not only about watts printed on the box. The charger and phone must “talk” using the same protocol:
for example USB Power Delivery (PD), PPS, or Quick Charge.

• Recent iPhones mainly use USB PD.
• Many Samsung models can use PD and PPS.
• Some cheaper chargers only do basic 5V/2A or an older Quick Charge standard.

If the protocol does not match, the phone falls back to basic slow charging, even if the charger claims “65W” or more.

2. Weak or Damaged Cable

Cables matter. Inside the cable, the copper wires need to be thick enough for high current.
Very cheap or old cables have high resistance and heat up instead of delivering power.

• A 100W charger with a poor cable might only deliver 10–15W effectively.
• Bent or crushed cable ends are especially suspicious.
• Some USB-C cables support fast data but only low charging current.

3. Dirty, Loose or Corroded Charging Port

Pocket lint, dust, small metal particles, or moisture damage can interfere with the connection inside the port.
Even if the cable “clicks in”, some pins may have poor contact.

We see many phones where a careful professional clean of the port immediately restores normal fast charging.
In more serious cases (corrosion, liquid damage), the port or board may need repair or replacement.

4. Battery Health Is Too Low

When the battery is worn out, the phone’s software often limits charging speed to reduce heat and risk.
This is common in devices with battery health below around 80%.

Replacing the battery can restore both battery life and safe high-speed charging,
especially on older iPhones and Android devices used for several years.

5. Overheating and Thermal Protection

Phones slow down charging when they get too hot. This can happen when:

• Charging in direct sunlight or a hot car.
• Using a thick or insulated case while charging.
• Gaming or watching videos during charging.
• Using wireless charging pads that already generate extra heat.

When the phone is hot, the system lowers the charging power or even pauses it
until the temperature returns to a safe range.

6. Background Apps Eating Your Power

Sometimes the phone is actually charging at a decent rate, but heavy background activity hides it.
System updates, cloud backups, app downloads, location tracking, or social apps syncing in the background
all draw power while the phone is trying to charge.

The result: the battery percentage barely moves, even though the charger is working hard.

Simple Checks You Can Try at Home First

1. Test with a known-good original charger and cable
   If possible, borrow an official charger/cable set that matches your phone brand and test the speed.
2. Inspect and gently clean the port
   Use only a dry, non-metal tool (for example a wooden toothpick) very gently, or leave it to a technician.
   Do not spray liquid into the port.
3. Take off the thick case and keep the phone cool
   Charge in a cool room, away from sunlight, and avoid heavy use while charging.
4. Check battery health (if your phone shows it)
   On iPhone, go to Settings → Battery → Battery Health & Charging.
   If the maximum capacity is low, a replacement battery may be the real solution.
5. Close heavy apps and pause large downloads
   Update and backup when you have time, not when you urgently need a fast top-up.

If charging is still slow after these steps, there is a good chance that the port, cable lines,
battery, or main board need proper diagnosis.

When to Visit a Repair Shop

Bring your device to us if:

• Charging speed suddenly dropped after a fall or liquid spill.
• The port feels loose or the cable wiggles easily.
• You see corrosion or green/white marks near the port.
• The phone sometimes charges, sometimes does not, with the same charger.
• Battery health is low and the phone also drains very quickly.

We can measure the real charging current, inspect the port under a microscope,
and check the battery and main board for damage. In many cases, a port clean, port replacement,
or battery replacement solves the “slow charging” problem without needing a new phone.

EziRepair – Christchurch & Auckland

Christchurch: 03 343 1078
Auckland Westgate: 09 392 0039
Website: www.ezirepair.co.nz

More Helpful Guides for Your Phone

If you are also having connection or mobile signal issues, these articles may help:

• 
  Why Your Phone Shows “SOS Only” or “No Service” in New Zealand
  
• 
  How to Check If Your SIM and Phone Still Work After the NZ 3G Shutdown
  
• 
  Why New Zealand Is Shutting Down 3G (and What It Means for Your Phone)