Mac charges slower when I use the power adapter extension cable

[collin_]

I've been using my power adapter extension cable for 7 or 8 years. It still looks brand new because I wash it with warm, soapy water whenever it starts looking dirty (being careful not to get water in the part that connects to the power bricks).

I sometimes charge my 16 inch MacBook Pro with the proper 96 watt brick, and sometimes with an Apple 30 watt brick (long story). When the 30 watt brick is plugged directly into the wall, it charges the Mac roughly 10%/hr under very light workloads. When it's plugged into the extension cable, it's much slower than this. When the 96 watt brick is plugged directly into the wall, the Mac's battery level is always increasing. When it's plugged into the extension cable, the Mac's charging sometimes pauses, and the battery percentage sometimes drains briefly.

Has anybody else experienced something like this? I don't see how this extension cable would "wear out," but that is what seems to have happened. Should I just buy a new one?

 

[Erehy Dobon]

Everything wears out.

There's no way to know for sure what happened but cables (and wires in general) do wear out. All metal changes over time and use.

All electrical conductors -- whether they be in your wall, your car or in consumer electronics -- lose some performance in time as heat alters the molecules. Heck, even your electric utility company replaces wires. My guess is that when a 20-year-old nuclear submarine goes into drydock for a complete overhaul the wiring is replaced.

Most likely the wiring is becoming loose where it is attached to either side of the cable (wall plug or charger plug) due to heat-related expansion and contraction of the wires. That also results in a higher risk of a short which could lead to a fire.

That's something to think about when you buy real estate: how old is the wiring? Fifty year old copper wires in my home's walls: the insulation is brittle as is some of the wire itself.

Note that the extension cable is not waterproof. If you introduced any liquid at the wire joints there's a strong possibility of moisture-related corrosion. That would exacerbate wiring connections at the plugs.

One can visibly see oxidation in old copper speaker wires with clear plastic insulation.

I suggest you purchase a new power extension cable both for performance and safety reasons.

 

[collin_]

Everything wears out.

There's no way to know for sure what happened but cables (and wires in general) do wear out. All metal changes over time and use.

All electrical conductors -- whether they be in your wall, your car or in consumer electronics -- lose some performance in time as heat alters the molecules. Heck, even your electric utility company replaces wires. My guess is that when a 20-year-old nuclear submarine goes into drydock for a complete overhaul the wiring is replaced.

Most likely the wiring is becoming loose where it is attached to either side of the cable (wall plug or charger plug) due to heat-related expansion and contraction of the wires. That also results in a higher risk of a short which could lead to a fire.

That's something to think about when you buy real estate: how old is the wiring? Fifty year old copper wires in my home's walls: the insulation is brittle as is some of the wire itself.

Note that the extension cable is not waterproof. If you introduced any liquid at the wire joints there's a strong possibility of moisture-related corrosion. That would exacerbate wiring connections at the plugs.

One can visibly see oxidation in old copper speaker wires with clear plastic insulation.

I suggest you purchase a new power extension cable both for performance and safety reasons.

Thank you for the info! I went ahead and ordered a new one directly from Apple.