USB chargers.

[G-CPTN]

Over the last year or so I have acquired various devices that come with a USB charger.

Not all have the same final termination, but most have a separate cable that plugs into a UK three-pin plug (that is, presumably, a transformer of sorts).

Is it safe to swap cables from 'transformer' to transformer (ie does a full-size USB socket have identical characteristics)?

What about using USB sockets in cars (and, now, buses)?

[TGR]

Output varies, but it's based on the charger, not the cord. Phones usually 1 amp, Tablets 2 amps. I use them interchangeably on Apple devices with zero issues. 2 amp charge will provide a fast charge on the phone. Hope it helps.

[henry_crun]

The device that looks like a UK 13A plug with a usb socket has an output of nominally 5V dc (usually 5.2V) with a capability of providing various amounts of oomph, 500mA, 1A, 2A. If you choose a 2A version it will do for all applications.

For comparison a standard computer usb socket can provide 500mA. Some equipment like hard drives or raspberries need 1A and have to be connected to two usb sockets in parallel. Er, not a happy arrangement.

Be sure to unplug the usb cable before turning the mains off. In some circumstances the unpowered charger can short the device battery. I had this happen to a Kindle and had some difficulty getting it going again. Shouldn't be possible but it did happen.

USB sockets in cars again should all be 5V. Some devices come with chargers that plug into the cigar lighter socket, again these should produce 5V dc. Be sure that your device is isolated from the rest of the car, and not plugged into anything else.

[G-CPTN]

Many thanks.

[Keef]

Recent mains ones are unlikely to be "transformers" - those have been pretty much universally replaced by switch-mode power supplies.

Some advantages - most SMPS don't care whether you plug them into 110 volts or 230; they are pretty efficient, and usually don't get as hot as a transformer when on heavy load. Disadvantages are that if they let go, they will probably take the device being charged with them (byebye iPad), and the cheaper ones cause interference on radio/television/WiFi.

[FullOppositeRudder]

..... the cheaper ones cause interference on radio/television/WiFi.We had an initially puzzling example of this recently with a dual USB output adapter cigarette lighter plug in automobile 1 (hers). The device was being used for the first time to power the sat-nav device. Our favorite FM radio station was 'weak' and overwhelmed most of the time by white noise. Eventually it dawned on me to remove the adapter. Result? noise gone, station returned to full quieting, and domestic peace returned.

I endorse everything else offered above about charger ratings etc. The usb concept is finding it's way into all kinds of applications - my micro model glider needs a USB outlet to charge its micro sized battery.

FOR

[Capn Bloggs]

For tablets (Android Micro-USB types that need ~2amps), I have found there are USB leads and USB leads. Even though the charger may be rated at 2amps, some leads won't give that to the tablet (it gives a message about low charging rate), whereas others will.

[Bushfiva]

Just to add to the confusion, sometimes the labelling itself is misleading: a couple of my chargers are marked 1.1A and 2A, but in fact they'll each supply 2.5A to a suitably dumb device. Internally, they're configured so that one port will present itself as a 1.1A charger, and the other will present itself as a 2.0A charger, to the appropriate Apple device.


Finally, I have USB cables that are internally set to do the same thing with any charger.


It took a cheap USB current monitor to work out what the heck was going on in my growing collection of chargers.

[TWT]

And some el cheapo mains operated USB chargers can kill you.

A woman picked up her phone to make a call while it was plugged into the charger and was electrocuted.The charger was an unapproved, illegal import that she got cheap.

[henry_crun]

Yes, most 'wall wart' chargers with smps are to some extent live. Best to avoid use in kitchen or bathroom where you may inadvertently complete a circuit from charger to earthed metalwork.

When you run a finger along a wart-powered dab radio antenna you can usually feel the tingle of a safe very low current mains shock.

[Keef]

Chargers and cables both can make a difference.

I had to make up a "special" lead for my iPad so that it would charge properly after the Apple charger disappeared and I tried to use a different 2 amp one. The iPad needs specific voltages on the inner pins - easily fixed once you know. The genuine Apple charger does it inside the charger; a fudged lead will achieve the same.

"Wall warts" that cause interference are likely to have other problems. I bin them and make a note not to use that brand again. 12 volt input ones that make a noise get taken into my radio shack and fixed.