USB chargers.

The USB charger my wife uses says 12W 2.4A and 5.2V but I thought USB stood for Universal Serial Bus? so there will be a standard current 500 mA USB 1.0 and 2.0 and 900 mA for USB 3.0. So at 900 mA my sockets rated 2.1A for pair should be ample for any USB charging, it should not need 2.4A.

The Ipad which the charger was supplied with is reported on some web sites as needing 2.1A so likely OK,

The whole idea was to free up 13A sockets and if the Ipad does not comply with the USB standards then the whole idea is flawed. The question is USB really universal and can one safely plug stuff into USB charger outlets?

Charging is a different matter. Many devices will happily use in excess of 1A if told they can.

http://www.usb.org/developers/docs/usb20_docs/usb_20_031815.zip

As I understood it (could well be wrong) I thought you could use any USB charger with any compatible device, it's just that some chargers are worse (less powerful) than others so will take longer to charge. Rather than some chargers being avoided for fear of damaging the device.

Unfortunately this isn't always the case, I saw a programme on telly the other day regarding some USB chargers overcharging batteries in ecigs causing them to explode!

Spark123 said:

Unfortunately this isn't always the case, I saw a programme on telly the other day regarding some USB chargers overcharging batteries in ecigs causing them to explode!

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That would be the fault of the ecig..

Monkeh said:

Spark123 said:

some USB chargers overcharging batteries in ecigs causing them to explode!

Click to expand...

That would be the fault of the ecig..

Click to expand...

That would be true ONLY if the USB charger was supplied with the E-cigarette as the intended charger.

Charging a battery correctly and safely requires a source of power and a controller to regulate the current pushed into the battery. This control is necessary to control the rate at which chemical action takes place in the battery's cells. If the chemical action is too fast the battery will suffer and in some cases explode.

Sometimes the charger has the controller built inside which makes it suitable only for charging those batteries the manufacturers designed it for.

Sometimes the controller is built into the battery and in theory these batteries will tolerate a range voltages from power sources and still charge correctly

And sometimes the controller is a human who sets the current /voltage level according to the battery and when the battery starts gassing realises it is fully charged.

You cannot connect just any random power supply or battery charger to a battery and expect trouble free charging. The battery and the controller have to be compatible with each other.

bernardgreen said:

Monkeh said:

Spark123 said:

some USB chargers overcharging batteries in ecigs causing them to explode!

Click to expand...

That would be the fault of the ecig..

Click to expand...

That would be true ONLY if the USB charger was supplied with the E-cigarette as the intended charger.

Click to expand...

If the thing comes with a cable which lets you plug it into a USB port, it gets to deal with all the charging. The USB port, whether it's a host port or a charger, cannot act as a battery charger, it can only supply power.