We need a special Samsung USB cable to charge at 2amps?

[extraclass]

I have a side job driving cars for automobile dealers and some trips are long. I have had to use my S-4 for navigation and this really drains a battery! I thought I had the correct charger in my go bag but I have had a few surprises. Some of the new cars do not have a lighter socket but most have usb ports. My Samsung cable would not charge my phone using the USB charger socket! So I have done some testing!
The Samsung charger will not work with all USB cables and the Samsung cable will not work with all USB chargers. I purchased one of those USB testers on Ebay that tells you the voltage and current and it made my experiments easier. I have not found a combination that will actually charge at more that 1000 Ma. Usually my S-4 and Tab 3 charge at around 700 to 800 Ma. If the lightening bolt is seen in the battery icon it is charging at a faster charge rate. If plugged into a USB port on my computer my S-4 charges with about 150 Ma and the lightning bolt is not visible.
Apple and Samsung use a scheme to tell the phone or tablet that the charger is capable of high speed charging. The two schemes are different in older chargers and Apple chargers may not charge your phone at a fast rate! The little cheap 2.1 Amp rated lighter chargers work fine if used with the right cable. Experiment before you hit the road for a long day.