PSA: Thunderbolt 3 cables longer than 0.5m generally don't support USB 3.1 speeds



  • Reply 61 of 63
    Mike WuertheleMike Wuerthele Posts: 6,585administrator
    marcmandy said:
    This is a good article, but it still leaves me confused. I am looking to extend the charger for my new macbook pro without using the long, thick a/c extender for travel.

    I have the 6' usb-c to usb-c charging cable for the brick but found it too short in this particular instance where there was no desk in the room I was in. I was hoping to buy a 10' or 3 meter cable which would've done the trick but can't seem to find one that actually specifies 87w (or 100w). I gather from what I see above, there is no direct correlation between thunderbolt 3 - thunderbolt 3 and wattage either.

    I found one on Amazon (USB-C to USB-C Cable (10ft/3m) - uni USB-C Charge Cable [5A] for MacBook Pro 2018/2017, iPad Pro/MacBook Air 2018), but it has an 11% 1-star rating which seems kind of high. It's rated a 5 amp. Is that what I should be looking for?

    Maybe I'm asking for the impossible...

    Thank you for the article and any assistance you might be able to provide. 
    You're better off using the Apple extender for the power adapter. Long, high-wattage USB-C cables, meaning longer than 6.6 feet, are explicitly disallowed in the spec.
  • Reply 62 of 63
    Thank you very much!
  • Reply 63 of 63
    Thank you for the great summary.  I have a Thunderbolt 3 compatibility issue you did not seem to touch on.  Connecting a Western Digital G-DRIVE Thunderbolt 3 to a 2017 iMac.  Works great with the 1 meter cable provided by G-Tech.  I bought a 2 meter Belkin cable that advertised 40 Gbps (same one Apple sells)  The G-DRIVE never shows up with the  Belkin cable.  What's worse is that after using the Belkin cable, I can't go back to the G-Tech cable unless I power down for iMac & drive for hours. Seems like some sort of self-protection reset?  Per your recommendation, I have a Pluggable 2 meter cable on order.  Guess I should have settled for a cheap & cheerful USB-C drive & cable.

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