Nexus 7 - USB 3 ?

50Twuncle

My (2013) Nexus 7 takes a long time to charge fully
I have read that the chargiing time can be reduced considerably by using a USB 3 cable
Is this true
And if so - is this just when charging from a USB 3 port on my PC or from the mains adapter as well ?

cajef

How long do you call a long time?

Mine takes about two hours from 15% charge to full using the mains adapter.

System

USB 2 or 3 makes no difference. No changes were made to the power connections between USB 2 & 3. Apart from which the USB connection on a Nexus is USB2 only so doesn't utilise the extra lines that USB3 has.

ciderboy2009

Are you trying to charge using a usb port or the charger?
The charger provided has the data lines disconnected which indicates to the Nexus that it can use high speed charging (ie: pulling a greater current than the 500ma allowed from a usb port).
If you want to charge quickly from an alternative charger then you may need a cable with these lines disconnected (I've got one to allow fast charging whilst in the car).

50Twuncle

ciderboy2009 wrote: »

Are you trying to charge using a usb port or the charger?
The charger provided has the data lines disconnected which indicates to the Nexus that it can use high speed charging (ie: pulling a greater current than the 500ma allowed from a usb port).
If you want to charge quickly from an alternative charger then you may need a cable with these lines disconnected (I've got one to allow fast charging whilst in the car).

I have tried both - both take about 6 hours from 1/4 charge !!
What about wireless charging - have any of you tried that ?

S0litaire

what charger are you using?

It should only take 6 hours if it's using a adapter with a rating of 0.8amps or less (my kindle charger is .5 or .8 and it takes an age to charge my nexus 4 or 7 using it

The Official ASUS charger for the latest Nexus7 should read : 5.2v = 1.35a

The old Nexus7 model had a slightly more powerful adapter, Think it was 5.2v = 2a

If your are charging from a USB socket on your PC then it will only get 500ma (which is why it's taking so long to charge)

USB3 in a PC can supply more power to devices. But I'm not sure if they would transfer the extra power over a standard USB2 cable (the port might look the same but it has an extra row of contacts only a USB3 cable can use.)

If you can, try a double USB Y-cable. it can plug into 2 usb sockets and give 1a of power to your phone, that should cut down charging time on a PC.

cajef

S0litaire wrote: »

The old Nexus7 model had a slightly more powerful adapter, Think it was 5.2v = 2a.

Correct, it is actually 5.0v = 2a, I should have stated in my post that mine is the earlier model.:o

50Twuncle

Surely - a device only draws what current it requires dependant on it's resistivity ?
ie) I = V/R
So - if the voltage is constant (and obviously the resistance of the device is fixed) - how can the device draw more current ?
Standard USB voltage is 5v (+/- 0.25v).


You can't force more current down a line - the current is the result of a PD between two points

bod1467

I think it's more a case that the current is limited by the source ... it has a maximum capacity. If the device needs less than the maximum then it'll only draw less - if it can take more than the capacity then the charging source will limit the current draw, irrespective of whether the device wants more.

S0litaire

But the phone battery charging circuits are designed to pull as much amps as possible while charging.

so if the USB socket provides 500mA the phone will pull 500mA
if you plug it into a 2000mA charger it will pull 2A.

Note Li-Ion batteries can get VERY warm when charging at higher amperage and it can, over time, damage the battery if you use a larger ampage than it was designed for.