3 ms·

They’re shit. The inrush current is so high it actually damages the plugs with arcing!

by cjsuk 9y ago

artursapek 9y ago
You must have bought yours on Amazon :)
- cjsuk 9y ago
  No from the Apple store. See my other post. This is poor design, regardless of where it came from. There should be a hefty NTC or inrush current limiter in the charger.
  - nixgeek 9y ago
    Have you looked at an 87W USB-C charger to see if this was addressed with the latest generation of laptops?
    - cjsuk 9y ago
      Not yet. I’m not due for a hardware refresh for about a year yet. I’ll probably head in the direction of Lenovo then.
abritinthebay 9y ago
You're describing the cheap Chinese made knock-offs. They look almost perfectly identical and generally you can only tell by opening them up. They're awful. There are a LOT of teardowns of those. It's scary.
- robin_reala 9y ago
  I bought a MacBook on eBay that came with a fake charger. Had to threaten to report them before they sent me a real one.
  - lostlogin 9y ago
    I hope you then reported them.
- cjsuk 9y ago
  No you are completely 100% wrong. This was one that came with a MacBook Pro from the Apple Store actually in the sealed box when I bought it. Don't assume I'm stupid. I'm actually a qualified electrical engineer and I know switching power supply topologies and design very well. Don't assume that because 90% of the charger is well designed, the rest of the 10% is. There is no or insufficient inrush protection in the charger. This results in a hefty current flowing the charge the primary DC cap in the switching power supply when you plug it into the wall (step response of a capacitor at DC is high instantaneous current if the source impedance is low such as rectified AC - derived from I=C(dV/dt), dv=350, dt -> 0, C~10mF, I->infinity in an idea model ignoring parasitics and series resistance of capacitor). This damages the pins and stresses the diodes terribly reducing the time to failure. Google inrush current protection. You do NOT get this on decent industrial switching power supplies that actually cost less. They either have NTCs or pre-charge. The Chinese ones are a whole different story. Some of those are absolutely abysmal and are in no way even comparable to the Apple ones. The Apple ones certainly don't rank that high really in the scale of things, regardless of all the love spread over the Internet. If you're comparing them to a lowest bidding turd from China, then of course they're going to look good. Here's a picture of the burn marks on the pins: https://i.imgur.com/aaHV1kX.jpg https://i.imgur.com/aaHV1kX.jpg I'm not going to even go into the three left IO boards I've replaced on MBP's where the magsafe connector has burned out.
  - abritinthebay 9y ago
    I stand corrected sir! It did sound a lot like you were describing the common issues with the knock offs though - however with the extra detail it really cleared it up, thanks for that.
  - ianhowson 9y ago
    > There is no or insufficient inrush protection in the charger There's at least a PFC chopper and fuse. I'd be surprised if there were no series inductors, though I can't spot them on http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr... It's a reasonably complex pre-rectification stage for a consumer device. It's certainly not AC->rectifier->DC cap. I can't explain the burn marks in the image -- stunning for a British plug. None of mine with Australian or European plugs show any significant burns. I see sparking when I plug it in, but that's standard for pretty much any SMPS.

They’re shit. The inrush current is so high it actually damages the plugs with arcing!

by cjsuk 9y ago

They’re shit. The inrush current is so high it actually damages the plugs with arcing!

artursapek 9y ago

You must have bought yours on Amazon :)

cjsuk 9y ago
No from the Apple store. See my other post. This is poor design, regardless of where it came from. There should be a hefty NTC or inrush current limiter in the charger.
- nixgeek 9y ago
  Have you looked at an 87W USB-C charger to see if this was addressed with the latest generation of laptops?
  - cjsuk 9y ago
    Not yet. I’m not due for a hardware refresh for about a year yet. I’ll probably head in the direction of Lenovo then.

abritinthebay 9y ago

You're describing the cheap Chinese made knock-offs. They look almost perfectly identical and generally you can only tell by opening them up. They're awful. There are a LOT of teardowns of those. It's scary.

robin_reala 9y ago
I bought a MacBook on eBay that came with a fake charger. Had to threaten to report them before they sent me a real one.
- lostlogin 9y ago
  I hope you then reported them.
cjsuk 9y ago
No you are completely 100% wrong. This was one that came with a MacBook Pro from the Apple Store actually in the sealed box when I bought it. Don't assume I'm stupid. I'm actually a qualified electrical engineer and I know switching power supply topologies and design very well. Don't assume that because 90% of the charger is well designed, the rest of the 10% is. There is no or insufficient inrush protection in the charger. This results in a hefty current flowing the charge the primary DC cap in the switching power supply when you plug it into the wall (step response of a capacitor at DC is high instantaneous current if the source impedance is low such as rectified AC - derived from I=C(dV/dt), dv=350, dt -> 0, C~10mF, I->infinity in an idea model ignoring parasitics and series resistance of capacitor). This damages the pins and stresses the diodes terribly reducing the time to failure. Google inrush current protection. You do NOT get this on decent industrial switching power supplies that actually cost less. They either have NTCs or pre-charge. The Chinese ones are a whole different story. Some of those are absolutely abysmal and are in no way even comparable to the Apple ones. The Apple ones certainly don't rank that high really in the scale of things, regardless of all the love spread over the Internet. If you're comparing them to a lowest bidding turd from China, then of course they're going to look good. Here's a picture of the burn marks on the pins: https://i.imgur.com/aaHV1kX.jpg https://i.imgur.com/aaHV1kX.jpg I'm not going to even go into the three left IO boards I've replaced on MBP's where the magsafe connector has burned out.
- abritinthebay 9y ago
  I stand corrected sir! It did sound a lot like you were describing the common issues with the knock offs though - however with the extra detail it really cleared it up, thanks for that.
- ianhowson 9y ago
  > There is no or insufficient inrush protection in the charger There's at least a PFC chopper and fuse. I'd be surprised if there were no series inductors, though I can't spot them on http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr... It's a reasonably complex pre-rectification stage for a consumer device. It's certainly not AC->rectifier->DC cap. I can't explain the burn marks in the image -- stunning for a British plug. None of mine with Australian or European plugs show any significant burns. I see sparking when I plug it in, but that's standard for pretty much any SMPS.