charging a Nokia phone (C2-01) from USB. Need enough power.

[this piece is a  place marker for people searching on "how to" charge from USB.
 Short answer: Plug in any modern phone and it's supposed to "Just Work".]

A couple of weeks ago I bought an unlocked Nokia C2-01 from local retailer Dick Smith's.

I wanted bluetooth, 3G capability and got a direct micro-USB (DC-6) connector too.
I bought a bluetooth "handsfree" for my car as well. It came with a cigarette-lighter charger with a USB socket and a USB mini (not micro) cable.

I remembered that all mobiles sold in the European Union were mandated to use a USB charger [MoU in 2009, mandate later] and thought I'd be able to use the car-charger for everything: phone, camera, ...

The supplied 240V external phone charger worked well for the C2-01.
But I couldn't get it to charge from the in-car USB charger.

Turns out the handset charger could only supply 400ma, not the 500ma of the USB standard. Bought another in-car USB charger from Dick Smith's: works fine with both.

What had confused me was the phone wouldn't charge when I tested it with my (old) powered USB hub. Is it old and tired or was the phone already fully charged?? Need to properly test that.

I hadn't tried it with my Mac Mini, jumping to the unwarranted conclusion "this phone doesn't do USB charging". When tested, worked OK directly with the Mac...

There's one little wrinkle.
Devices like the iPad that charge from USB take more than 500ma (700ma?) - which Mac's supply, but are more than the standard. [Why some USB adaptors for portable HDD's have two USB-A connectors.]

I know a higher current has been specified for USB - but can't remember the variant. Is it just the new "USB 3" or current "USB 2" as well?