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Comment on Apple’s Vision Pro battery pack is hiding the final boss of Lightning cables

abhibeckert@lemmy.world ⁨7⁩ ⁨months⁩ ago

I think it’s reasonable.

First of all they didn’t want to put a battery on the headset. Fair enough, even without a battery it’s heavier than most headsets.

That decision means the cable doesn’t just need to provide average power consumption, it also needs to be able to handle peak power consumption. Chances are it’s somewhere inc the vicinity of a Mac Mini - which has a 185 Watt power supply.

USB can provide up to 240 Watts, however it needs relatively high voltage to do that over thin cables permitted in the USB specification. 48 Volts for 240 Watt power delivery and 20 Volts for 100 Watts.

Vision Pro is only 13 Volts - which means that cable almost certainly has much thicker internal power cables than most USB cables. If you tried to power a Vision Pro over a standards compliant thin USB cable it would likely be a fire risk.

Apple could have made it work with a USB cable but they would have had to use 48 Volts, and that likely would’ve meant transforming the 48V power supply down to 13 Volts which is needed by the headset… and voltage changes are not free. You lose power, which means less battery life from the same size battery. Again - battery life is an area where Vision Pro isn’t really good enough already. They didn’t need to do anything that makes it worse.

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apemint@lemmy.world ⁨7⁩ ⁨months⁩ ago
There’s nothing reasonable about these assumptions.

There’s no way the VisionPro gets even close to 100W. Why? Because heat dissipation. The vast majority of power drawn by semiconductors is dissipated as heat and, in a device that’s strapped to someone’s face, there’s simply no way to dissipate hundreds of watts.

Also, knowing the battery pack size and battery life, it’s easy to guesstimate the power consumption.

“The Apple Vision Pro provides approximately 2 hours of battery life. Based on its size, the internal battery capacity is estimated to be within 20,000mAh (74Wh), resulting in an overall power consumption of around 30W.”

Even if we assume the double of that 30W, it’s well within USB-C standards.

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- player2@lemmy.dbzer0.com ⁨7⁩ ⁨months⁩ ago
  Very good explanation. If usb-c is good enough for a MacBook, it’s definitely good enough for a small headset - no excuses!
  
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XeroxCool@lemmy.world ⁨7⁩ ⁨months⁩ ago
I think you’re confusing volts and amps. Higher amperage wire has thicker copper conductors. Higher voltage wire has better insulation and some standards about how far connections have to sit. Raising voltage increases the chance of sparks, but amperage is what runs into heat problems with modern insulation. Wattage (power) is simply Volts x Amps. To get higher wattage, you can increase volts or amps (or both of course), depending on what materials and devices you have available. The whole point of going to higher voltages in usb is to carry more power without making the cables thicker and without overheating thin wires.

Most circuit boards are 5v. I’m sure Apple already has a converter on board. Also, the DC conversion problem is outdated - both on difficulty and inefficiency. Solid state devices are able to switch power on and off at a frequency to make an onboard converter coil work with the same efficiency as AC. The little extra heat lost from the switchers is made up for by not wasting time/energy on phase cycling. Check out “buck buck” converters.

Volts, amps, and watts are all different units and do not interchange. They are related, but serve different functions.

Fun fact: powerlines all use much higher voltages on the transmission wires than what you have in your house. The lower amperage (but same wattage) uses less material for wiring and loses less energy as heat along the way. North American houses have 120v, the transformers on the nearest telephone poles drop it from 440v, and the overhead lines are 440,000v with various possibilities in between substations

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CucumberFetish@lemm.ee ⁨7⁩ ⁨months⁩ ago
That’s… not how it works.

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BeatTakeshi@lemmy.world ⁨7⁩ ⁨months⁩ ago
Congratulations

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- abhibeckert@lemmy.world ⁨7⁩ ⁨months⁩ ago
  For what?
  
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  - CucumberFetish@lemm.ee ⁨7⁩ ⁨months⁩ ago
    On buying their bs
    
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    bruhduh@lemmy.world ⁨7⁩ ⁨months⁩ ago
    tenor-202100372
    
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HelloHotel@lemm.ee ⁨7⁩ ⁨months⁩ ago
That makes sense.

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iarigby@lemmy.world ⁨7⁩ ⁨months⁩ ago
Thank you for the explanation

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