Phone charging cables and time to charge!

I have a 3.1 amp USB charging socket built into a couple of twin 13A sockets, I also have some 4.2 amp but only 2.1 amp per pair.

Hanging out of the socket was a standard 5 pin micro USB lead, plugged in wife's phone and a while latter it was still only 33% and she commented that the night before it had charged faster from the satellite box then it was now doing from a 3.1 amp outlet.

I realised the night before she had unplugged my hard drive which has a wider plug with extra connections so I swapped leads and then the phone went to 70% in less than an hour. Why was the wider cable so much faster?

USB devices charge by default at a slow rate which will take forever.
Devices have various methods of determining if the charger can supply higher current and will then charge at a more sensible rate.
Different manufacturers have their own ways of doing this, and unless the charger and device are designed to operate together, it's anyone's guess as to whether it will charge quickly or not.

The rating printed on chargers is mostly irrelevant.

Poor quality leads can also have a significant effect.

Have lots of built in chargers in my home , they vary in performance , some only support one device at a time and trying to use both ports can result in little or no charge.

Two Samsung leads for the Samsung devices seem to have cured the problems. I think real problem is Smart phones use so much power, my simple mobile phone lasts 4 or 5 days and charges in 4 or 5 hours, it's the tablets and phones my wife has which cause the problem, I got fed up with every socket having a charger plugged in, so I got USB sockets now it seems the reason for so much being on charge was due to cheap leads, everything was taking so long they were left plugged in 24/7.

Most cheap leads are made from copper coated ali, and won't transfer much of a charge. I give my daughter poundland leads because she leaves her iphone plugged in all the time (and brekas them quickly), but I only use the supplied or kosher leads with my phone, as they'll give a full charge in about an hour.