A Galaxy S20 that will not charge may have a dirty port, a worn cable, a weak charger or a battery that has reached the end of its life, and at six years old the last of these is a real possibility. Start with the port. The USB-C port collects pocket lint, and a plug that does not seat fully will not charge. With the phone off, use a wooden toothpick to lift the lint gently, never a metal pin. Try a different cable and a different adapter, and plug the adapter into a wall outlet and not a computer port.
The checks in more detail
Look for the charging icon and the lightning bolt on the screen; if the phone says it is charging slowly, the cable or adapter is weak, since the S20 can fast charge at 25 watts with a suitable adapter. Check for moisture. The S20 can detect water in the port and refuse to charge, showing a message; dry the port by leaving the phone unplugged, face down, in open air for several hours, and do not use rice or a hair dryer.
If wireless charging works but wired does not, the port is the suspect. Restart the phone, and try charging while it is switched off. A phone that has been fully discharged may need to charge for ten or twenty minutes before the screen responds, so leave it connected. If the phone charges but the percentage stays low or falls quickly, the battery is probably worn. In Samsung Members, Phone diagnostics, Battery status, you can test it.
A battery replacement is usually cheaper than a new phone, and Samsung or a repairer can do it. Heat matters as well: the phone slows or stops charging when warm, so take it out of a case and out of the sun. Update the software. If the phone swells, the back lifts or the screen bulges, stop using it and take it to a repair shop, because a swollen battery is a risk. When every cable, charger and a clean port fail, a port or board repair is needed.
Differential
Likely causes of “Samsung Galaxy S20 family will not charge or charges slowly”, and how to tell them apart
- 1
Lint in the port
What separates it The plug does not seat
How to confirm Clean the port gently with a wooden toothpick
- 2
A worn cable or weak adapter
What separates it Slow or no charging
How to confirm Try another cable and a wall adapter
- 3
Moisture in the port
What separates it A water warning appears
How to confirm Dry the phone and wait
- 4
A worn battery
What separates it The percentage falls quickly
How to confirm Test in Samsung Members and replace the battery
- 5
A damaged port or board
What separates it Nothing helps
How to confirm Repair
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether wireless charging works
- The cable and adapter
- Any water message
- The battery status in diagnostics
Try in this order
0 of 6 completedClean the port
ReversiblePhone off.
Try another cable and adapter
ReversibleIn a wall outlet.
Check for a water message
ReversibleAnd dry the port.
Try wireless charging
ReversibleTo test the port.
Test the battery
ReversibleIn Samsung Members.
Repair
ReversibleIf nothing helps.
Model-specific
What is true of this model and not of its siblings
- Six years old
- The battery may be worn.
- Port
- Lint is the commonest cause.
Stop boundary
When this stops being a self-service repair
- !If the case or screen bulges, stop using the phone
- !If nothing works, take it to a repairer
- !Back up if the phone starts
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why will my S20 not charge?+
Lint, a cable or a worn battery.
Can it detect water?+
Yes, and it may refuse to charge.
How fast does it charge?+
Up to 25 watts with a suitable adapter.