5 ms·

It does matter that you're putting more current over the cable than it's designed for. Overloading conductors can be a melty, flamey time.

by lowboy 10y ago

seanmcdirmid 10y ago
I think it just charges slower, it doesn't magically pump 87 watts over the cable, just 60.
- prodmerc 10y ago
  Only if it detects it uses a 60W cable. Which I really doubt. You can pump 100 watts through a 60W rated cable - it will probably work because the rule is "users are dumbasses, rate it for 60 on paper and 120 in reality". Or it could heat up, maybe to the point of damage.
  - liuhenry 10y ago
    It's a whole 60W A/C adapter package, not just the cable. The adapter isn't pumping out more wattage than it's rated for.
    - lowboy 10y ago
      It doesn't look like it. All of the pictures show just a cable, and the description has > In the box: BreakSafe USB-C cable with quick disconnect magnetic connector
    - seanmcdirmid 10y ago
      Yes, just because you charge up a computer with a 60W A/C adapter but it can take 87W, doesn't mean the A/C adapter is all of a sudden putting out 87W. The cable itself doesn't create more or less flow.
  - jsjohnst 10y ago
    You guys really should spend a few moments doing a quick google search before responding. USB doesn't just magically deliver power, its negotiated between the device and the power source. In the case of USB-C, the cable is involved in the negotiation. See slides 7&9 here specifically: http://www.usb.org/developers/powerdelivery/PD_1.0_Introduction.pdf http://www.usb.org/developers/powerdelivery/PD_1.0_Introduct... More details here: http://www.usb.org/developers/powerdelivery/ http://www.usb.org/developers/powerdelivery/
    - voltagex_ 10y ago
      Until that negotiation doesn't quite work right. https://plus.google.com/+BensonLeung/posts/TkAnhK84TT7 https://plus.google.com/+BensonLeung/posts/TkAnhK84TT7
- pantalaimon 10y ago
  How do you know? There is nothing in the cable that would prevent the current from flowing.
  - deleted 10y ago
    [deleted]
- yuubi 10y ago
  The default condition of cables is that they can conduct much more current than is safe, and it takes extra effort to limit this. (Yes, there's a limit to what you can put through a wire, but it's enough to melt the metal, and you wasn't too avoid softening the plastic around it.) If you put twice the rated current through a cable, the conductors will handle it just fine. However, the resistance of the wires will dissipate 4× the power the insulation is designed for (twice the current times twice the voltage drop), and the inside of the isolation will get somewhat warmer. How much of a problem this is in real life depends on the ambient temperature, the thermal conductivity of the insulation, jacket, and wire, the temp the plastics can withstand, etc. The safe thing is to use wire from a vendor that rates it honestly to conservatively, and start within the ratings.
- DSteinmann 10y ago
  > I think it just charges slower, it doesn't magically pump 87 watts over the cable, just 60. Please do not post such dangerous unsubstantiated comments which illustrate your lack of understanding of basic electronics principles. Recommending a cable rated for 60W for an 87W scenario puts peoples lives at risk. Nothing "magical" about that either. You are unconsciously incompetent. Take a USB cable and touch both ends to the terminals on your car battery if you want a dramatic learning experience. Wear gloves, long sleeves, and eye protection.
  - emp_zealoth 10y ago
    It should still have 87W through, might heat up a tiny bit more, but I really, REALLY doubt that a power cord rated for 60W would be unable to handle 87W too, the safety margin would be way too low. Also, your dramatic learning experience is dumb, shorting a car battery will do probably do a few hundred amperes, two orders of magnitute more than in any laptop charger ever...
- justaaron 10y ago
  i live offgrid and observe my 13" MBP with an 85w power supply actually pulling around 10-19 watts during typical usage...(my inverter has an output readout) FWIW... doubtless heavy gaming would be different... compiling gets it up to the upper 30s...
jakobegger 10y ago
USB cables use resistors to indicate how much current they are rated for, so the charger would limit the current to avoid melting your cable. (That's why out-of-spec cables are dangerous)

It does matter that you're putting more current over the cable than it's designed for. Overloading conductors can be a melty, flamey time.

by lowboy 10y ago

It does matter that you're putting more current over the cable than it's designed for. Overloading conductors can be a melty, flamey time.

seanmcdirmid 10y ago

I think it just charges slower, it doesn't magically pump 87 watts over the cable, just 60.

prodmerc 10y ago
Only if it detects it uses a 60W cable. Which I really doubt. You can pump 100 watts through a 60W rated cable - it will probably work because the rule is "users are dumbasses, rate it for 60 on paper and 120 in reality". Or it could heat up, maybe to the point of damage.
- liuhenry 10y ago
  It's a whole 60W A/C adapter package, not just the cable. The adapter isn't pumping out more wattage than it's rated for.
  - lowboy 10y ago
    It doesn't look like it. All of the pictures show just a cable, and the description has > In the box: BreakSafe USB-C cable with quick disconnect magnetic connector
  - seanmcdirmid 10y ago
    Yes, just because you charge up a computer with a 60W A/C adapter but it can take 87W, doesn't mean the A/C adapter is all of a sudden putting out 87W. The cable itself doesn't create more or less flow.
- jsjohnst 10y ago
  You guys really should spend a few moments doing a quick google search before responding. USB doesn't just magically deliver power, its negotiated between the device and the power source. In the case of USB-C, the cable is involved in the negotiation. See slides 7&9 here specifically: http://www.usb.org/developers/powerdelivery/PD_1.0_Introduction.pdf http://www.usb.org/developers/powerdelivery/PD_1.0_Introduct... More details here: http://www.usb.org/developers/powerdelivery/ http://www.usb.org/developers/powerdelivery/
  - voltagex_ 10y ago
    Until that negotiation doesn't quite work right. https://plus.google.com/+BensonLeung/posts/TkAnhK84TT7 https://plus.google.com/+BensonLeung/posts/TkAnhK84TT7
pantalaimon 10y ago
How do you know? There is nothing in the cable that would prevent the current from flowing.
- deleted 10y ago
  [deleted]
yuubi 10y ago
The default condition of cables is that they can conduct much more current than is safe, and it takes extra effort to limit this. (Yes, there's a limit to what you can put through a wire, but it's enough to melt the metal, and you wasn't too avoid softening the plastic around it.) If you put twice the rated current through a cable, the conductors will handle it just fine. However, the resistance of the wires will dissipate 4× the power the insulation is designed for (twice the current times twice the voltage drop), and the inside of the isolation will get somewhat warmer. How much of a problem this is in real life depends on the ambient temperature, the thermal conductivity of the insulation, jacket, and wire, the temp the plastics can withstand, etc. The safe thing is to use wire from a vendor that rates it honestly to conservatively, and start within the ratings.
DSteinmann 10y ago
> I think it just charges slower, it doesn't magically pump 87 watts over the cable, just 60. Please do not post such dangerous unsubstantiated comments which illustrate your lack of understanding of basic electronics principles. Recommending a cable rated for 60W for an 87W scenario puts peoples lives at risk. Nothing "magical" about that either. You are unconsciously incompetent. Take a USB cable and touch both ends to the terminals on your car battery if you want a dramatic learning experience. Wear gloves, long sleeves, and eye protection.
- emp_zealoth 10y ago
  It should still have 87W through, might heat up a tiny bit more, but I really, REALLY doubt that a power cord rated for 60W would be unable to handle 87W too, the safety margin would be way too low. Also, your dramatic learning experience is dumb, shorting a car battery will do probably do a few hundred amperes, two orders of magnitute more than in any laptop charger ever...
justaaron 10y ago
i live offgrid and observe my 13" MBP with an 85w power supply actually pulling around 10-19 watts during typical usage...(my inverter has an output readout) FWIW... doubtless heavy gaming would be different... compiling gets it up to the upper 30s...

jakobegger 10y ago

USB cables use resistors to indicate how much current they are rated for, so the charger would limit the current to avoid melting your cable. (That's why out-of-spec cables are dangerous)