Are USB chargers... universal?

I have a cell phone that charges off USB and an mp3 player that also does. The phone came with a charger, the player not. Presumably because I’ll be spending so much time with it connected to the computer trying to get the software to work that charging will be well sorted. My question is, could I charge the player off the phone’s charger? Could I charge either of them from say the charger of another phone? Does the USB connection guarantee power requirements or could the phone manufacturer use the same physical connection but deliver its own power requirements?

For what it’s worth I’ve been doing this for a while without problem. Whether or not it’s a good idea is another question! YMMV - I’ll be interested to hear from someone whoknows

The Chinese government mandated that all mobile phones should use a standard USB charger with USB connector and voltage and any manufacturer who would use the standard USB connector for a different voltage would soon have a lot of problems from customers.

A wall to USB charger should always work but note the cable from USB to device will probably be different. (I believe the Chinese government wants to mandate mini-USB for the other end.)

Charging directly from a computer might have its problems with devices which require more current. A computer USB port will give 100 mA with no questions asked but it can negotiate up to 500 mA. If the device is recognised by the computer then it should supply the requested current up to 500 mA but if it is just a dead load the current will be limited to 100 mA.

Any wall or car adapter whould supply 500 MA without problem.

In summary, it is extremely improbable that any manufacturer would use a USB charger at a different voltage.

What sailor said. I would assume any USB charger to be capable of supplying at least 500mA at 5V. I would spend several seconds in mute shock and several minutes swearing should I find a USB adapter supplying anything other than 5V.

It’s of course technically possible, but unbelievably unbelievable that anyone should do such a thing.

Mototola Razrs while they havea mini-USB power jack will only work with USB (mini plug) power adapters that have a Motorola ID chip. Generic min-USB power adapters will not be accepted by the phone as chargers even if they fit the slot. If min-USB to USB cable is used off a notebook USB port you have to have a Motorola driver to charge the phone.

According to Dell guys I know, USB’s have an industry standard charge that they pull.

Well, not really. That is just an extreme simplification adequate as a customer service response. Thay can pull anywhere from zero to a max which depends on the type of device. That is from the computer USB port. A self-powered device can pull whatever it wants or needs.

I can charge my Razar off of any USB cord that I have laying around. I have used the cord to my camera to charge my phone at work. Since there are about 2.3 gajillion models of Razars, YMMV

Cord and charger are different things. What you are saying does not necessarily contradict astro although what he posts does seem odd.

And your display screen does not pop up with "unauthorized charger’?


I just tried my V3 with the charger that came with my USB player (Wall Outlet to Mini-USB) and it does indeed pop up “Unauthorized Charger”.

Now I’m wondering if I can use the wall charger for my Motorola W37g to charge my Sansa Clip mp3 player. There are times when I travel without my laptop but do have the mp3 player, and I really don’t want to have to buy a separate charger for it.

I am not sure if this is just a way to get you to buy their chargers or if there may be a legitimate reason but it definitely is a point against Motorola (which has lost market share steadily).

It seems that the phone only wants to be connected to an intelligent device and go through the whole handshake process.

As explained, when connecting to a computer USB port the device can only draw one unit and has to request and negotiate for more whereas a simple wall or car charger will supply as much as needed without further question.

It seems the V3 wants to be connected to something which pretends to be a computer? Definitely a point against it.

The V3 and V3m use the mini USB port for data transfer and and playing sound as well so this supposition is probably correct as it’s a multi function port.
Here’s a an article/post I wrote on hacking the V3M.

I dont understand. All the phones I have and know use the mini-USB port for data transfer as well as charging. If I connect my phone to the computer USB port then the phone and the computer detect each other and can transfer data (if I want). But if I plug the phone into any “USB” charger then it just charges but it does charge. It does not need to transfer data to charge. All the phones I know are like that.

interesting… guess what phone I have :frowning:
I had tried to charge it off a ‘generic’ charger, and while it lit up and seemed to acknowledge a power source, it didn’t actually charge; I tested it by disconnecting it and plugging into the computer right away and it started charging. I was confused. Now less so. Motorola. :mad:

The Chinese mandate is intriguing… I’ve long wondered why this hasn’t been the case, USB makes a lot of sense as a standard (until idiots like Motorola come along :mad:).

I also used to have a motarola razr, don’t remember the exact model but it would give the unauthorized charger message when I used it with a generic USB car charger. It would still charge with the unauthorized charger but IIRC it charged much slower than it should have.

Ok people, the AC adapter that you plug into the wall will (should!) have an output current listed on the adapter itself. I have a Motorola (L3?) phone and an HP PDA that both charge through USB mini jacks. The AC adapters, though, have different output currents, so I would NOT interchange those (even aside from the “unauthorized charger” issue). I charge both using the same cable to my computer because the device driver on the computer knows what the device needs and will provide it automatically.

This makes sense and can be explained knowing how the USB power works as explained above. As soon as a USB device is plugged into a computer it has one unit of current available but it needs to request and negotiate if it wants more. The phone does this with the computer but with a dumb charger it cannot negotiate anything so either (a) the phone just continues to charge at one unit or (b) the phone is intelligent enough to figure out that since there is no response on the data bus it can assume it is connected to a dumb charger which can supply more than one unit of current so it can start charging at five units or whatever it needs. Pretty much all modern USB chargers will be able to supply more than enough current for this application.

Nope, never seen it.