Can I charge other devices with the iPad power adapter?
August 5, 2010 2:51 PM Subscribe
Can I plug any old USB cable into the 10W USB Power Adapter that came with my iPad and use it to charge other devices? Or will I fry something in the process?
I use that adapter to charge my iPhone and iPad and have not fried anything. And my Kindke too.
posted by dfriedman at 3:21 PM on August 5, 2010
posted by dfriedman at 3:21 PM on August 5, 2010
Best answer: If it's a standard USB connection, it should be fine. Lots of devices are charging of USB these days. The maximum wattage shouldn't be relevant. The only issue would be if the charger uses a different voltage which I think is really unlikely.
If you think about it in terms of plumbing, resistance is like the size of a nozzle, and voltage is like the pressure. The higher the pressure, the faster water comes out. Or you could increase the size of the nozzle (thereby lowering the resistance) and more water comes out.
The maximum wattage is kind of like the width of a pipe. If you have a 6 inch nozzle, but only a 1-inch pipe leading up to it, you're only going to get "1 inch" worth of flow at a given pressure.
Anyway I personally think it's really unlikely to fry anything.
posted by delmoi at 3:46 PM on August 5, 2010 [2 favorites]
If you think about it in terms of plumbing, resistance is like the size of a nozzle, and voltage is like the pressure. The higher the pressure, the faster water comes out. Or you could increase the size of the nozzle (thereby lowering the resistance) and more water comes out.
The maximum wattage is kind of like the width of a pipe. If you have a 6 inch nozzle, but only a 1-inch pipe leading up to it, you're only going to get "1 inch" worth of flow at a given pressure.
Anyway I personally think it's really unlikely to fry anything.
posted by delmoi at 3:46 PM on August 5, 2010 [2 favorites]
oddly enough, I was using that charger to charge my droid phone, and it seemed be charging slower than over regular USB on my pc or my nook charger. mine just might be broken or something though
posted by yeoz at 3:49 PM on August 5, 2010
posted by yeoz at 3:49 PM on August 5, 2010
yeoz, as it turns out, to draw maximum current, the droid expects the data lines (D- and D+) to be shorted together.
posted by fake at 4:02 PM on August 5, 2010 [1 favorite]
posted by fake at 4:02 PM on August 5, 2010 [1 favorite]
Best answer: The charger supplies 5 volts to the portable device, the same as a regular USB port, so it cannot harm the device. The only question is how much current the device is allowed to draw. In the original USB spec a device could only draw a maximum of 100 milliamps until the host talked to the device and gave permission to the device to draw up to 500 milliamps. The charger doesn't have USB intelligence so can't talk to the device and give it permission in the normal manner.
So they released a new battery charger spec for USB in 2007. Manufacturers have been slow to adopt the new spec so it will depend on your device. The new spec gives devices a way to determine the power capability of the charger without actually talking USB. The device receives 5 volts from the charger and drives 5 volts out the D+ data line. The device sinks current on the D- data line through a resistor. If a charger is connected, the charger shorts D+ and D-. This means that the device will see the same voltage on D+ and D-. This tells the device that a high power charger is attached and allows the device to draw more current to charge its battery -- up to 1500 mA. If a low power hub is attached, D+ and D- are not shorted and the device knows it can only draw 100 mA.
The answer is that you can safely plug any USB device into the charger. However, whether the device will draw 100 mA or 1500 mA depends on whether the device is new enough to support the USB battery charger spec. This means that the device has enough intelligence to test the D+ and D- voltage. Older devices do not have this ability. Some older USB devices won't charge the battery at all unless connected to a real PC hub.
posted by JackFlash at 5:01 PM on August 5, 2010 [5 favorites]
So they released a new battery charger spec for USB in 2007. Manufacturers have been slow to adopt the new spec so it will depend on your device. The new spec gives devices a way to determine the power capability of the charger without actually talking USB. The device receives 5 volts from the charger and drives 5 volts out the D+ data line. The device sinks current on the D- data line through a resistor. If a charger is connected, the charger shorts D+ and D-. This means that the device will see the same voltage on D+ and D-. This tells the device that a high power charger is attached and allows the device to draw more current to charge its battery -- up to 1500 mA. If a low power hub is attached, D+ and D- are not shorted and the device knows it can only draw 100 mA.
The answer is that you can safely plug any USB device into the charger. However, whether the device will draw 100 mA or 1500 mA depends on whether the device is new enough to support the USB battery charger spec. This means that the device has enough intelligence to test the D+ and D- voltage. Older devices do not have this ability. Some older USB devices won't charge the battery at all unless connected to a real PC hub.
posted by JackFlash at 5:01 PM on August 5, 2010 [5 favorites]
I use my iPOD charger to charge it, my Nokia N97 Mini, and my Kodak Zi8. I see no reason why this would fry anything.
posted by ethnomethodologist at 9:39 PM on August 5, 2010
posted by ethnomethodologist at 9:39 PM on August 5, 2010
if it corresponds to the USB power draw spec, it may signal for power at the level it was made for.
similar to fake's link, ">this should tell you about your apple 10w usb.
i would plug it in with no fear. too many amps is fine, too many volts fries devices.
posted by overbo at 10:00 PM on August 5, 2010
similar to fake's link, ">this should tell you about your apple 10w usb.
i would plug it in with no fear. too many amps is fine, too many volts fries devices.
posted by overbo at 10:00 PM on August 5, 2010
This thread is closed to new comments.
posted by turaho at 2:55 PM on August 5, 2010