All micro usb cables are not created equal?
September 29, 2011 11:05 AM   Subscribe

Why does the motorola branded micro usb cable that came with my droid phone both charge *AND* transfer data, but generic micro usb cables will only charge the phone?

Recently got a Motorola Droid phone. It included a motorola-branded micro usb cable. I can use it to charge the phone and also transfer data back and forth between the phone and a computer.

I just bought some cheap, non-branded micro usb cables to sprinkle around home and work so I'd always be able to charge the phone. However, I've noticed that the non-branded micro usb cables will NOT transfer data, only charge.

Both cables appear to have the same number of metal contacts on each end.

So what gives, why does the motorola cable allow data transfer and the generics do not?
posted by de void to Computers & Internet (11 answers total) 2 users marked this as a favorite
None of my generic ones have this problem.
posted by Big_B at 11:13 AM on September 29, 2011

I never had this problem with my Droid Eris. I used a generic USB cable I pulled out of a drawer to both charge the phone and transfer data. The cable that came with the phone I stuck in my backpack so I'd have it when I traveled, I never used it otherwise.

I know that on the Eris, there was a setting for charging the phone versus using it as a disk. Maybe that setting is causing you issues, but it seems weird that it works with the official cable and not a generic one.
posted by ralan at 11:20 AM on September 29, 2011

Response by poster: I didn't specify my Droid model - it's a Droid Bionic. I assure you generic micro-usb cables will not transfer data on mine.
posted by de void at 11:21 AM on September 29, 2011

Best answer: You wrote "some cheap, non-branded micro usb cables" maybe they are too cheap?
Try another make, as all cables are not equal?
posted by lungtaworld at 11:25 AM on September 29, 2011

I've asked my sister, who is not only a Droid Bionic owner, but also the supervisor of the mobile phone department at the local branch of a large American big box electronic retailer. She is going to see if she can find the answer, and let me know later. It may be later tonight or early tomorrow before I have her reply, though.
posted by ralan at 11:36 AM on September 29, 2011

Response by poster: Whoops, looking like my assurances aren't worth anything.

I went around and collected all 4 of the generic USB cables, tested them one by one and found one that *DOES* transfer data. So it looks like I have 2 out of 3 of defective cables and also a cable from a "wall wart" usb charger that only does power BY DESIGN.
posted by de void at 11:42 AM on September 29, 2011

I have a generic usb cord that has two heads - one for data transfer and one for charging (common connection to the computer, different connections to the phone). I think that yes, sometimes people just want to charge their phones. I know I only bought mine (also from wall wart) because it was the only kind in stock, not because I wanted to transfer data.
posted by hydrobatidae at 12:09 PM on September 29, 2011

There is a resistor network that signals to your Droid to charge at full current. Normal USB cables will only charge at a low rate or sometimes not at all. The resistor network is different for Apple devices.

I have a blog post detailing how to modify Apple-style chargers for Droids that goes over some of this.
posted by fake at 12:10 PM on September 29, 2011

I've only noticed that (some) generic cables have trouble maintaining contact connection, but it's good to know about the transfer/charge difference.
posted by rhizome at 12:44 PM on September 29, 2011

Yea, it's a USB quality thing. Interesting datapoint:
Samsung android devices are capable of charging at 750mAh instead of just 500, however without modification basically only Samsung cables work this way...the phone sees it as "AC charge" versus just "charge."

The trick is that in the android based chargers, pins 2 and 3 are shorted, and the phone can see this as it checks (I'm supposing) continuity and automatically switches over to 750mAh mode, assuming the adapter can push that much.

Even "quick" chargers that say they can push up to 900mAh or 1A will only push 500mAh because it's all the phone will allow---unless pins 2 and 3 are shorted. (You can also cheat and do it in the cable or at the plug, but doing it in the charger is a much safer option.

Sorry for the derail.
posted by TomMelee at 1:12 PM on September 29, 2011

Just heard back from my sister, and she says that some of the cheaper USB cables they sell are "charge only". So that may be part of the issue.
posted by ralan at 5:15 AM on September 30, 2011

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