The truth is, this problem affects every smartphone after some time regardless of the brand, and usually for the same reasons. In this article, we'll show you why your smartphone charges slowly, and what you can do about it.
Suspect number one - your cable:
The first offender in any case of slow charging should always be your USB cable. Just take a look at it: guilty as hell. Considering the awful treatment my USB cables undergo, it's no wonder that it is usually why my phone won't charge faster. USB cables get bent, twisted, coiled, run over with chair wheels and generally abused: all of these are not very good for maintaining a solid connection and flow-through of power.
Be sure to check the ends too: they can very easily get full of fluff. Cables aren't immune to physical wear and tear and the USB connector itself also gets worn and can feel loose when you plug in your phone. If the cable that came packaged with your device isn't reliable anymore or you've simply lost it, beware of buying the cheapest charging options online. Higher quality cables have copper wire some cheapest use aluminum and other substitutes that don't hold up as well and thicker rubber enamel around the wire, making it more resistant to damage.
The power source:
The next obvious question is where are you getting your power from? If you have a USB cable plugged into your laptop then your phone is going to charge insanely slowly and you'll deserve it. Likewise with Qi wireless charging, which we know from the newest flagships from Samsung, LG, and Google for example. While Qi is a brilliant technology, that brilliance comes at the cost of speed. Your best bet is to have your phone plugged directly into mains power at the wall socket. However, even this can be problematic, especially if you're in an old building where the wiring might be a little sketchy.
The charger/power adapter may not be right
To complete the trifecta, if it's not your power source or your cable, chances are that it's the actual adapter you're using that is causing your battery to charge slowly. There's a reason every manufacturer provides a specific USB adapter for each phone they ship.
Switching adapters between phones can mix-match voltage, wattage, amperage and so on. This is why it's best to stick with the adapter that came with your phone or at the very least take a look at the fine print and replace it with another adapter of the same type.
Your phone itself:
Sorry, but it's true. If you're sitting there wondering why your Galaxy S5 takes so long to charge it's probably because the old-timer is getting worn out after many years of use. Newer processors not only support fast charging, but newer phones even come with turbo charging chargers. Many newer cell phones can get you four hours' worth of usage after just ten minutes plugged in.
Other phones that support fast charging will have a lightning bolt icon on the charger itself, possibly along with turbo charging output figures. Your phone can also become a pocket lint cave too, so check your port and make sure the little flap in the port isn't bent while you're looking in there.