Your tablet or mobile phone is really loading as it should? The source, the cable or even the device may be the problem. You can discover the defect using a USB current and voltage meter like this one below, that's pretty cheap and useful.
The gadget is simple: has a USB input and an output, you put between the source (or PC USB) and the cell phone or tablet. So he can measure the load voltage and current during charging.
See only the equipment already plugged into the PC's USB measuring voltage, that was in 5.2 V. It also has a timer that measures how much of current passed and for how long, measurement known as ampere hour (or Milli ampere hour) estimating the carrying capacity of a battery.
See the device in detail: in the upper left the voltage Tester V 5.20 bookmarking, on the lower left the current meter, on the top right and bottom timer the mAh.
Just plug my phone and the USB voltage low to 4.98 V. The charging current is 0.42 to. Low for a cell phone, will load slowly.
If I plug my phone into a source of good quality (a 40W blitzwolf) the chain on to the 1.1, and the battery will charge faster. See my source keeps 5.15 V even with load.
And if you plug in a low-quality cable? Even at the source, This thin cable that I have low charge current to 0.1 and almost does not load anything. EWw!
I liked the tester, can I put in the car and check any charger, fonts, USB outputs and cables that I want. For only 5 U.S. dollars, worth it. I leave below link to the product: