Charging mobile phones is mystery

[Sheep221]

I thought when I got my xperia mini last summer that charging time is quite long and slow with stock charger, so I bought additional 3 chargers and effect is weird.

Listing:
1. SE stock - 850mA label/500 reality - 2.5 hours charge time
2. SE retail - 550mA label/650 reality - 1,2 hours charge time
3. HTC retail - 1A label/400 reality - 3 hours
4. Samsung retail - 700mA label/250 reality - 5hours

Either in good or bad way I'm quite confused about the big difference between real and labeled output current. I would expect 1A adapters to provide no less than 900mA and so on.
I want to know if someone has this similar experience, or can recommend something that charges fast(with fixed cable preffered).
Charging current measured with battery monitor widget so some small inaccuracy is there.

 

[Bateluer]

How are you determining actual mAh vs rated?

 

[Sheep221]

As I said I measured it via battery monitor application running on the phone. When the app is running it displays the drawn current.

 

[wirednuts]

i dont know, i would suspect moreso that some adapters are fast charging and reaching their capacity. other chargers have the capacity but the phone isnt going into fast charge mode.

 

[magomago]

So since USB is an differential signal, to enable fast charging with most smart phnes, the charger's Vsig+ and Vsig- need to be shorted.

If they aren't, it assumes its a standard USB interface and limits draw to USB spec. If they are shorted, it assumes you aren't connected to a true USB protocol, and that they can go ahead and exceed USB interface specs.


If you search Amazon you'll find this to be a balls huge issue for many chargers: many advertised "high speed" chargers actually are actually limited on this point. To get the 1-2A current draws, people will literally crack them open, and short the pins; or they will crack open the cable and short the data lines.

edit:

this assumes the rest of the HW is bottle necked by this point.

 

[Sheep221]

Well I can try to open the chargers but not sure if it will be ok as the cover and plug seem to be melted together.

Another question is, are the chargers with fixed cables also having the signal conductors? Not sure if yes or not.

 

[boomhower]

Try an Apple iPad charger, 2A.

 

[Yuriman]

You can change the charging current via software if you have your phone rooted. By default on my Galaxy S2, "AC charge current" is 650ma, "misc charge current" is 450ma, and "USB charge current" is 450ma. I don't recommend increasing the USB charge rate because USB ports typically only put out 500ma and you could potentially cause problems / do damage.