Difference in charge time between charger and USB cable?

[TurboFool]

I'm aware that charging devices via the USB cable is generally painfully slow due to the voltage those cables are capable of.

That said, what's inherently different about the USB charger and does it, indeed, charge faster than plugging the device into the computer?

Right now I'm at work, and my lovely new 6800, only halfway through my work day, is at 20% battery life. Now to be fair it's brand new, so I've been tinkering with it nonstop, and that's likely to drain it faster than the way I'll be using it in, say, two months. Still, it badly needs a charge, and my AC adapter's at home because I charge it at night.

I've plugged it in into my computer via a USB cable we have at the office, and it's charging damn slowly (not helped by the fact that the phone keeps turning itself back on for no apparent reason and seemingly not turning itself back off despite the two minutes I have it set to when plugged into external power), as I know it does over USB to the computer.

So I'm trying to decide whether the USB cable to my computer is enough, or whether buying a second AC adapter is going to benefit me in any way (faster charging, or maybe preventing this thing from turning itself on all the time if that is, indeed, being caused by it being connected to the computer).

Also, if I do buy a second AC charger, any recommendations on the cheapest good quality one (I assume a generic one like those designed for the RAZR would work)?

Thanks!

[luv2chill]

The issue here isn't the voltage, which is the same for any miniUSB-plug charger. It's the current. Computer USB ports pass a max of 500mA over each port. If you have a look at the charger that came with your phone, it supplies 1000mA (or 1A), which in theory should mean that it will recharge your phone's battery twice as fast (all else being equal).

Sometimes 500mA isn't even enough to keep pace with the battery drain if you are actively using the device (esp the CDMA or Wi-Fi radios). If you have to charge via USB then you should keep the device's screen and all radios off to whatever degree you can.

I would suggest just picking up another 5V 1A miniUSB charger somewhere--you can get an OEM one if you want but you'll pay more. One hint is that the charger for the PPC6700 will work fine so you can find one of those easier/cheaper than if you bought one that is an "official" 6800 charger.

I don't recommend the Moto ones unless you've already bought one. I don't believe they can supply 1000mA (I think the highest I've seen was 800mA). That won't hurt your phone or anything, but it will charge your battery slower than the device was intended for.

[boe]

I notice a HUGE difference between the USB and the charger which wasn't the case with the 6700. I used to always use the USB cable to charge my 6700 because it would hold a charge. Typically took about 2 hours to charge via usb. I believe it takes about 9 hours to charge the 6800 via usb cable but just two to three via ac charger.

[Shaska]

Oh yeah, By far, the AC adapter will always charge faster then USB cables, Unless someone wants to take a USB cable from a "Seagate FreeAgent Go" Drive that has 2 Male usb plugs on one end for just that reason and try that... :P

[Pibe38]

Uhmm although I have not made any real tests, my USB cable seems to be charging much faster than what some users have reported here.

I haven't really compared it to my AC adapter, but I'm pretty sure the AC adapter will always be faster.