USB Charging Guide

usbchargers 1 USB Charging Guide

USB has been the standard for charging pretty much any small electronic gadget for years now but there is still some confusion about both what USB charging means in regards to compatibility and how you can charge USB equipment without a computer. Read on for a breakdown on USB charging.

The concept of USB charging

Many people ask for advice when it comes to USB charging becuase they’re unsure if a certain charger etc will work with their device. The answer can be both yes and no. We’ll come back to the “no” part later, but first off there are a few basic concepts that are important to understand about USB.

USB is basically the computer equivalent of an AC outlet, but standardized worldwide not just for certain countries. The standard USB power rating will be 5V 500mA which means that a device connected will receive 5V and be able to draw a maximum of 500mA (milliampere). To do a crude metaphor, think of the voltage as the type of power and the mA as the amount.

What this means is that you will never fry your device using a working USB port as USB is 5V and USB powered devices draw 5V. What you may run into is a lack of mA. External 2.5″ hard drives for instance tend to use 6-700mA which most computers will be able to provide, but not all. Also, some USB ports found on DVD players, car stereos etc are only 100-200mA. If your USB device requires more than what the USB port can provide mA wise, it won’t work but nothing bad will happen. It might also be that it will charge, but do so at a slower rate. At the same time, if the USB port provides more than what the device needs, it will work fine and nothing bad will happen.

The exception to this might be if someone has made chargers than use USB connectors but other voltages. I haven’t seen any such chargers, but considering how companies like HTC abuse the miniUSB port on their devices for things it’s not made for I wouldn’t be surprised. If you’re in doubt you can simply check the charger to see if it says 5V, but this is absolutely an exception (and theoretical one at that) not the rule.

The bottom line is that no working USB will damage your device. The worst thing that can happen is that it won’t charge it due to not providing enough mA or for another reason I’ll come back to, but that’s it.

Blocked USB charging

The “no” answer to the question above comes with something some manufacturers including Apple, Creative, Sony and others have started doing with their players: blocking USB charging. Basically this is a method of ensuring that you can only charge the device using a computer or a company charger. A USB cable has 4 pins, two for power and two for data. When connected to a computer, all 4 are in use. When connected to a standalone charger, only the power pins are in use. What some companies do is disable charging if there is no data activity so that you have to use a computer. If they provide their own official chargers that don’t use a computer, they often put in some small hardware trigger like having the two data pins connected inside the player which the player then recognizes and knows it’s an official charger.

This is a very bad thing to do for any manufacturer and just shows how greedy some of them has gotten. It totally defeats the purpose of having USB when you still need expensive official chargers to charge the device without a computer, but unfortunately a lot of companies do this. If you find yourself with a player that won’t charge off something like a USB AC charger that is able to provide enough mA, this is probably the reason, so be sure to check forums before buying a device if you want to use standard USb chargers.

Charging accessories

As you might have gathered from the above explanations there are ways of charging USB devices without using a computer. The cheapest, most common method is to use a USB AC adapter which is basically a plug you plug into the wall socket with a USB port on it to plug your device into. As long as you have a player that doesn’t block this, it’s by far the cheapest way of getting power to your device. You can find these at your local electronics store, but I tend to order them from DealExtreme since they have Soshine chargers there which are both cheap and very good quality. They have both a US version, European version and a UK version and I can personally attest to these working well.

usbchargers 1 USB Charging Guide

Another common USB charging accessory is the car equivalent of the USB AC charger. Just plug it into a car cigarette socket and it gives you a USB port to charge from. Again I got mine from DealExtreme, but while it’s not as common as the USB AC type of chargers you should be able to find one pretty easily more or less anywhere that sells electronics.

usbchargers 2 USB Charging Guide

Lastly you have various battery packs that provide USB power. Basically these are packs that either have a rechargable battery, AA/AAA batteries or even solar panels that spit out USB power for your device. You can get these in any shape or form, from cheap emergency chargers to more expensive ones and not to mentioned heavy duty ones. Grahm reviewed the second one of these just last week. I’d highly recommend a durable, high quality recharger one and not one that run off AA/AAA batteries as the rechargeable ones are generally more reliable. Especially packs that use 4 batteries can be a bit shaky since the cheap ones don’t always have power regulators. This means that it feeds the 4×1,5V = 6V directly into the USB connector without downscaling to 5V. This doesn’t matter for most equipment out there, but there have been reports of such packs frying devices.

Bottom line

The bottom line is that USB charging is perhaps the most universal method of charging something ever as it can be done from any USB socket regardless of country or other “normal” limitations. With the exceptions of greedy companies blocking USB charging, you can be sure that any USB chargers you buy will work with your gear. I highly recommend getting some of the types of chargers mentioned here as they are cheap and very useful the day you find yourself without power and a computer.


Ahmad on August 11, 2009 5:12 PM

What kind of guide is this? I learned nothing from it. I was expecting a guide on which devices use the “blocked” charging method.Like when I wanted to charge an iPhone 3G and had to use resistors to connect the data wires together.

Andre on August 11, 2009 6:02 PM

‘some small hardware trigger like having the two data pins connected inside’I believe having the data pins connected to each other is in the latest USB specification for charging. I had to interconnect the D+ and D- pins inside my USB AC charger to get it working with my Zune. Perfectly according specs but frustrating enough.Check the wiki under power:

Laerte on August 11, 2009 7:49 PM

I think its mA, not mAh.

Butch Meatstick on August 11, 2009 8:32 PM

You mispelled USB in the first sentence ;)

tstep182 on August 11, 2009 10:51 PM

Good article-thanks!

darkham on August 11, 2009 10:52 PM

for the sansa fuze?

Andreas Ødegård on August 12, 2009 12:20 AM

@Butch fixed :) @Ahmad: This is a feature article, which is timeless. Beside the hours upon hours which would be needed to find what players have blocked charging (since its not part of the official specs) the list would be obsolete and serve no purpose after a new device has been launched. We have a giant forum where poeple can get up to date information about the current devices on the market, this is just to have a timeless basis to work off of.

gebal on August 12, 2009 7:34 AM

Might it be worth pointing out that the xbox 360 is a practical USB charger?Most people dont seem to turn it off at the wall and a fair few have the console in their room, so as long as the brick has that orange light on you have a great charger there.I personally use this, and I’m aware of both ipod and alternate brand users who also charge via their 360.

aXit on August 12, 2009 7:47 AM

Amperes (amps) are are the unit of measurement for current, which is how many electrons are passing through a point per second. You’re definitely meant to be using mA in the above article, not mAh. Milliamp hours are really only used in battery capacity ratings, nothing to do with a port that can supply power.

ITrush on August 12, 2009 9:10 AM

Yes, almost all gadgets coming out already comes with USB charging and it’s really important to have atleast other accessories for extra options.

Andreas Ødegård on August 12, 2009 9:25 AM

@aXit: Thanks for that clarification, changed it to the correct term :)

Dromedary on August 12, 2009 7:01 PM

I also agree with Andre at 6:02 PM. This is the new standard.” A simple circuit in the charged device detects whether the upstream port is a charger that the new standards specify. If the upstream port is a wall charger, D+ and D– should short together, and the shorted node should float.”Also if connected to a computer the device needs to negotiate the current level or default to the measly 100mA.

Chris on August 12, 2009 11:43 PM

Still need to correct.”The standard USB power rating will be 5V 500mA which means that a device connected will receive 5V and be able to draw a maximum of 500mA (milliamp hours).”I assume you changed mAh to mA in the sentence above, but neglected to change the description to milliamps vs. milliamp hours (which refers to battery capacity).

Andreas Ødegård on August 13, 2009 12:16 AM

@Dromedary, Andre:I didn’t know there was such a standard, but that doesn’t really mean much. First off, companies sell the devices saying that you have to use the official charger to charge etc. Secondly, adding new specifications to an old standard breaks compatibility with so many devices (chargers) that it’s something they frankly should not do – they should have waited until USB 3 and done it then. A standard is great but doesnt mean much if no-one follows it, mp3 player and charger manufacturer alike. Half the players out there still charge fine from having the old method of doings things, and I’m not aware of anythign bad happening from it. I’d also dare say 98% of all charging equipment out there does not have the two pins connected as the standard suggests, leaving you with the end result that it’s more or less proprietary.@Chris yeah I didn’t see that, I just did a ctrl+f for “mah” and changed the ones that came up :s

Mike on August 13, 2009 12:37 AM

This is a great primer for those new to USB power, etc. Thanks for providing it!

Karan on August 13, 2009 7:35 AM

Nice guide. I always thought I would fry my clip by connecting it to my wd hd media player. Thanks.

Andreas Ødegård on August 14, 2009 8:11 AM

@Ivan I have that one (you can see it in the picture) and don’t recommend it. Beside being only 500ma vs 1000, the build quality is far from good like on the ones i linked to. Very flimsy

Tom on August 17, 2009 7:02 AM

like gebal said, xbox 360 works well if the power supply/brick has a orange light on. the wii is the same too if the wii has the amber “standby connected to wii24″ light on =]

MikeB on August 21, 2009 6:53 AM

In the UK, we can purchase different type of mains adaptors for charging via a USB cable.90% of chargers are Type 1, which means that only the 2 power pin connections are made.Look for Type 2/3 chargers, they have all 4 pin connections.

alfa on August 23, 2009 5:22 PM

dont buy any crative product,,!..i have bought creative vision m .they dont supply seperate cahrger,,they blocked the usb charging,,and more ..they dont provide a driver for w, vista..nice way to keep buyer a way!!

paul on August 24, 2009 1:18 AM

The real scam is the devices that use proprietary batteries in the first place. It is a never ending annoyance of mine. I absolutely LOVED my Sansa M260 because it was powered by a standard AAA cell. I used a nimh one which ran it for maybe 12 hours on a charge, and I had a few charged spares on hand so I could always pop in a fresh cell when necessary.Yes, I know that lithium batteries can give a thinner player. But unless the player is ultra tiny (eg. Sansa Clip, Ipod Shuffle) another mm or 2 doesn’t matter. I’d be very happy with an M260-like player with modern codecs and a MicroSDHC slot. Too bad no one makes it.A related topic: when you do your disassembly reports on lithium powered players, can you measure the device’s battery with a caliper and include the dimensions (height, width and thickness) in the report? That is useful in figuring out how to come up with replacement cells. A lot of these cells are replaceable with a carefully chosen cell phone battery that’s the right size, possibly with a little soldering to get the wires to the right place.

Moo on August 27, 2009 9:23 AM

May I correct you?if a device draws, for example, 500mA and the usb-port is some old one designed to provide only 100mA, it do can cause damage!not to the device thats supposed to be charged but to the device that is supposed to charge it.of course that will in most of the cases not happen, but if the supplying device is poorly crafted and thus does not contain some kind of over-current-protection, the device might just give what it has, even the 500mA at the cost of blowing up the internal power rectifier.

AndiX on September 12, 2009 3:56 PM

hi, what do you plug in FIRST?the USB-Charger to the walletor MP3-Player to USB-Charger?

gingtwat on September 16, 2009 8:33 AM

You probably should also mention that the mini-USB plug actually has 5 pins in it. This can be important as the extra pin (Pin 4) USB_ID is usually either connected to ground or left floating. Sometimes a pull up resistor needs to be added to from the USB_ID to Pin 1 (VDD) to select “Device Mode” rather than “Host Mode”. This resistor is in the device side plug as the USB_ID pin is not wired through to the PC side connector. The good news is that quite a few USB cables have this. So sometimes you can get round the not charging problem simply by trying out different leads and one may work rather than buying the manufacturers “special” cable. On some Creative players you can also solve this by pulling down both data lines (with 2x15k resistors) at the source to emulate what the host (PC) does when setting line speed. This is not so common.

Dan on September 30, 2009 10:34 PM

Overlooked is one extremely important thing: car chargers are dangerous to your equipment!!!The USB spec *is* 5V, but allows slew up to 5.25V. Car DC power is supposed to be 12V, but frequently run 14V. Cheap USB car chargers just convert the power on a ratio basis, not using the more expensive, but precise Zener diodes to set voltage levels. Because of this, they can run past the 5.25V USB spec and cook your battery. Buyer beware!

spooky on November 1, 2009 3:44 AM

What actually annoys me more than having to buy another charger because of “blocked” usb charging on a device is that I routinely travel with 7 music players and two smartphones all of which use usb for charging. If I could buy a couple of those plugs capable of plugging in 4 or more usb cables to an outlet I’d be carrying a little less stuff to keep track of and to find outlets for in my hotel room. Please don’t ask why I need all these devices for travel–trust me, I do. I also carry two Linux netbooks and a Macbook, all of which I DO need. You’re gonna need to trust me on that.

Lukas on November 7, 2009 9:07 AM

I would recommend this 2$ charger with EU plug at focalprice: seems to simulate a computer connection, my sansa clip goes in data transfer mode.

ömer on February 22, 2010 12:16 PM

This photo good but I don’t know which do …..

Antonio Flores on September 19, 2010 9:39 AM

The Universal USB Power Car Adapter you recommend delivers 1000 mA. Cant it fry the device?

Felix on February 9, 2011 12:00 PM

“If your USB device requires more than what the USB port can provide mA wise, it won’t work but nothing bad will happen.”

This is not strictly true. I once plugged a cheap hub into my PC. I don’t know how much current it tried to draw but it blew a track clean off the motherboard! Fortunately, the USB controller chip survived.

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