Europe backs call for universal smartphone charger

kwikbreaks

The only innovative thing I can see about the Apple lightning lead is the abysmal durability. I think they must be following the lead of the printer manufacturers who make all their profit on ink - Apple seem to have applied that principal to power leads. My granddaughter has gone through an alarming number in the few months she's had an iPod touch.

It seems she's not alone...

http://www.patentlyapple.com/patently-apple/2013/11/class-action-lawsuit-filed-against-apple-for-faulty-lighting-connector.html

securityguy

S0litaire wrote: »

All I know is when I plug my nexus4 phone into my nexus7 tablet charger, the phone heats up and it messes with the charge left readings.

Then something's faulty.

It's perfectly safe to plug, say, an iPhone (charges off a standard 500mA-capacity 5V USB charger, hence 2.5W) into one of those funky iPad chargers (5V, 2A-capacity, hence 10W).

The problem arises when you have a charger which has a high power capability and poor regulation, which instead of providing 5V into whatever load it's shown instead raises the voltage when the load is small.

Suppose a device presents a resistance of 10 ohms. You put a well-regulated 5V supply across it. 0.5 amps flow (V=IR), whether the supply has an ultimate capacity of 0.5 amps, 5 amps or 50 amps (I've charged batteries, old NiCads which will stand abuse, off big lab power supplies capable of insane currents). 2.5 watts of power (P=IV) are transferred.

Suppose a device presents a resistance of 1 ohm. You put the same well-regulated supply across it. Either 5 amps flow (again, V=IR) or fewer amps flow, because the power supply isn't capable of delivering the current (or, more usually, power). Either 25W of power are transferred (again, P=IV) or less, if the power supply isn't up to it.

The problem comes when the regulation is a bit rubbish. You take a big power supply intended for delivering a 5V@5A into a 1 ohm load, and when shown a 10 ohm load, instead of the rails being 5V apart, the regulation fails and they are 10V apart. This isn't uncommon: if you've got a high-impedence multimeter, measure the voltage across a USB charger. 1 amp flows (V=IR) and 10W are transferred (P=IV). Either the 10V blows up the device, or the additional 7.5W is dealt with by a voltage regulator and it gets very hot.

There is no problem in using large power supplies to charge small devices if the power supply is properly regulated (which is why the Apple chargers are quite expensive, as they do have decent regulation). The is some problem in using a large power supply with poor regulation if there's a regulator on the device, because it'll get hot. There's a major problem in using a large power supply with poor regulation to drive something that doesn't regulate its input, because it'll probably blow it up.

kwikbreaks

S0litaire wrote: »

think they are trying to standardise the power used

They can't do that sensibly. The total capacity of a tablet battery is a whole lot more than a phone battery so if you limited all chargers to USB level then tablets would take an age to charge up. I just use the same high power tablet charger for my tablet, phone, and Kindle. I've not noticed any excessive heating of either devices or charger. As per the above post if you do then it sounds like something is wrong.

securityguy

kwikbreaks wrote: »

They can't do that sensibly. The total capacity of a tablet battery is a whole lot more than a phone battery so if you limited all chargers to USB level then tablets would take an age to charge up. .

The ship's sailed with trying to standardise on existing USB 2.0 connectors, because there's plenty of reason for designers to move towards USB 3.0. Apple's Lightning is two lane, fast and can provide lots of power; USB3 has the same advantages. Mobile phone manufacturers aren't going to accept being limited to USB2 speed, because synch speed is something that people actually care about and as more and more laptops have USB3, manufacturers which support it on their mobile devices will get quite an advantage.

kwikbreaks

USB3 is only 900ma and that's too low for tablets too. I think the charger I'm using is 2.5A. The driving factor with phones and tablets seems to be the size of the connector. Unfortunately small connectors + sausage fingers = broken leads. I've never had issues with any of the USB based leads but imo both style Apple power leads I've had any experience with have been pretty shoddy - they stand up to sensible handling but not teenagers in a hurry.

I still think wireless could be the way forward if they can get the costs down and the charge rates high.

securityguy

kwikbreaks wrote: »

USB3 is only 900ma
.

USB Power Delivery is in the process of being standardised, and goes up to 100W.

http://www.usb.org/developers/powerdelivery/

kwikbreaks

That's a new one on me. Certainly my USB3 ports are limited to 900ma. Interesting that the standard is being changed but of course that won't help existing hardware. Be interesting to see what happens to existing USB3 leads if they tried to pass 20A too

securityguy

kwikbreaks wrote: »

That's a new one on me. Certainly my USB3 ports are limited to 900ma.

Apple have some non-standard stuff to deliver 1100mA out of USB2 or USB3 for various purposes (see here).

Be interesting to see what happens to existing USB3 leads if they tried to pass 20A

Luckily, they won't have to. If you want 100W, you have to take it at 12V or 20V, so it's only going to need to pass 8A at most. And you have to use a new detectable cable if you want to pass more than 5V or more than 1.5A anyway. So the glow-in-the-dark sight of a flimsy USB cable melting will have to remain an idle fantasy.

brightonman123

more anxed about rubbish battery life!

Mr_Toad

sillygoose wrote: »

Needs to go one step further for micro USB, put the flamin sockets the same way up on all devices!!!!

I have many devices and the socket varies across them, some the wider side faces front, others faces back. My eyesight without reading glasses isn't too good to see the shape of the socket so I often try it the wrong way before correcting. Unnecessary wear and tear on the plugs and sockets.

How is this going to help.

If you can't see which way up the socket is without your glasses how will you see which way up the cable is without them?

You'll be no better off. :rotfl: