be careful with usb cables - some are charge only, others are charge & data. my charge only cable can charge to full in about an hour. the charge & data cables are a lot slower at charging (4/5 hours full charge)
It doesn't work like that.
The maximum you can draw from a High-speed data port is 900mA, given the PC recognises the device. The typical maximum for a charge-only port is 1.8A. However that assumes
your charger and cable are both configured to present the correct D+ and D- voltages to the device you want to charge, for maximum charging current - and these specific voltages are different for different devices and manufacturers.
A charge-only cable may short or isolate the D+ and D- lines - that might be great for some devices that expect that, but for others that expect arbitrary voltages (e.g. iPhone with 2.8V/2.0V on the D+/D lines), you'll actually charge at a pretty damn low rate.
Summary: different devices respond differently to different chargers and cables.