# USB applicance charging speed **URL:** \ **Category:** Factual Questions\ **Created:** [May 1, 2010, 10:12pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985 "2010-05-01T22:12:01Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Draconis](https://avatars.discourse-cdn.com/v4/letter/d/c68b51/32.png) [@Draconis](https://boards.straightdope.com/u/Draconis)\ **Post date:** [May 1, 2010, 10:12pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/1 "2010-05-01T22:12:01Z")
I have a Nokia mobile phone (model not printed anywhere but bog standard phone) with an 830mAH 3.7V battery. It has a mini-usb connector which is used either for charging directly from the mains outlet or connecting via USB to a PC. When connected to a PC, it is trickle charged and takes perhaps 40 hours to fully charge. Can anybody explain to me why this is the case? I’m not sure about the capacity of my iPOD battery, but that fully charges via USB connection in a few hours. What am I missing? What’s the difference? Thanks all ---
**Author:** ![Draconis](https://avatars.discourse-cdn.com/v4/letter/d/c68b51/32.png) [@Draconis](https://boards.straightdope.com/u/Draconis)\ **Post date:** [May 1, 2010, 10:22pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/2 "2010-05-01T22:22:56Z")
Could a mod change “applicance” to “appliance”? Thanks 🙂 ---
**Author:** ![IAmNotSpartacus](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)\ **Post date:** [May 1, 2010, 10:28pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/3 "2010-05-01T22:28:15Z")
Most likely you’re using a USB port only supplying 100 milliamps of current at 5 volts. And running the phone at the same time. ---
**Author:** ![Draconis](https://avatars.discourse-cdn.com/v4/letter/d/c68b51/32.png) [@Draconis](https://boards.straightdope.com/u/Draconis)\ **Post date:** [May 1, 2010, 10:49pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/4 "2010-05-01T22:49:42Z")
> [@IAmNotSpartacus](#): > > Most likely you’re using a USB port only supplying 100 milliamps of current at 5 volts. And running the phone at the same time. So why does an ipod touch charge so quickly in comparison? Does it really require so much less power than a phone? ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [May 1, 2010, 10:54pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/5 "2010-05-01T22:54:48Z")
> [@Draconis](#): > > So why does an ipod touch charge so quickly in comparison? Does it really require so much less power than a phone? Your phone is transmitting and receiving data over long distances. Your iPod is not. In fact, your iPod uses almost no battery at all unless you’re playing it. The answer is yes. An iPod uses much less battery than a phone. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [May 1, 2010, 11:31pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/6 "2010-05-01T23:31:04Z")
Sounds like your phone isn’t asking for more power from the USB port: > **[USB in a NutShell - Chapter 2 - Hardware](https://www.beyondlogic.org/usbnutshell/usb2.shtml)** > > Details the hardware components of USB. This includes the connectors, Electrical, Speed Identification, Power, Suspend and Data Signalling Rates. > [@](#): > > A USB device specifies its power consumption expressed in 2mA units in the configuration descriptor which we will examine in detail later. A device cannot increase its power consumption, greater than what it specifies during enumeration, even if it looses external power. There are three classes of USB functions, … > > High power bus powered functions will draw all its power from the bus and cannot draw more than one unit load until it has been configured, after which it can then drain 5 unit loads (500mA Max) provided it asked for this in its descriptor. High power bus functions must be able to be detected and enumerated at a minimum 4.40V. When operating at a full unit load, a minimum VBUS of 4.75 V is specified with a maximum of 5.25V. Once again, these measurements are taken at the upstream plug. ---
**Author:** ![Draconis](https://avatars.discourse-cdn.com/v4/letter/d/c68b51/32.png) [@Draconis](https://boards.straightdope.com/u/Draconis)\ **Post date:** [May 1, 2010, 11:58pm UTC](https://boards.straightdope.com/t/usb-applicance-charging-speed/537985/7 "2010-05-01T23:58:20Z")
Actually, if I use my ipod while charging it it still charges fine. It has a wireless connection which I doubt uses a lot less than the mobile GSM connection. Seems like **Squink** hit the nail on the head and it’s due to bad design of the phone. Thanks a lot!