The problem occurs in various guises. Either your phone won't charge AT ALL when it is plugged in, or it only charges very slowly (sometimes barely faster than it is discharging). It’s a very common complaint, and one I’ve suffered from with devices myself, so here are a few solutions.
DIY USB port fix
The quickest, easiest, and often most successful solution, is simply to do a little DIY repair on your actual hardware. The problem is quite often that the metallic surfaces inside the USB port and the microUSB charger are not making good contact, either through a manufacturing defect or because of the continual plugging and unplugging of the charging cable.
All you need to do is shut down your device, remove the battery if possible and use something small, like a toothpick, to 'lever up' the little tab inside the USB port on your smartphone or tablet. Do so very carefully and gently, then reinsert your battery and plug it in again. Nine times out of ten this is all that is required.
The flimsiest part of a charger is of course the cable, not the adapter that plugs into the wall socket. If your device is having charging issues and the previous solution didn’t work, you might have a faulty cable. Before you rush out to buy a replacement adapter, just grab a spare USB cable from another device and try it instead. Quite often the cable will fray inside because it is constantly being curled up, stood on etc.
If the cable doesn't seem to be the problem, check the wall plug adapter, that may be the issue instead. Also, ensure that the same charger/cable combination works on a different device as this will help you eliminate the possibility that it is your device, not the cable or charger. iPhone users have their work cut out for them with the incredibly flimsy Lightning Port charger.
Clean up your act
Sometimes the reason a device is not charging correctly is because there is something lodged in the port, or there is just a lot of debris blocking the connection. Pocket lint, dirt and other minute rubbish can get into all sorts of nooks and crannies on a smartphone, so take a look to make sure there isn't something lodged inside the microUSB port (or in the charging cable either).
Of course, also make sure to never charge your phone near water or in excessively hot or humid conditions. Also, do not overcharge your device, charging overnight when your battery only needs 2-3 hours is a bad idea that can lead to a battery exploding or damaging your phone. Your phone has a cut-off switch for your battery, but sometimes this doesn't work. I figure it's better to be safe than sorry. Or burnt to a crisp.
Replace the battery
If your device is old, and the battery is struggling to hold a charge, it may be nearing the end of its life span. A new battery should last around two years before it needs to be replaced, although this depends on the number of charge and discharge cycles. If it seems necessary to replace it sooner than that, check your warranty, you may be eligible for a free replacement.
If your device isn’t very old, you may just have a defective battery. Remove your handset’s battery cover and ensure the battery isn't bulging or otherwise deformed or leaking. If it is, remove it immediately and clean the area carefully to avoid corrosion. If your cover is non-removable, you can lay the phone on the table and try spinning it, if the battery is faulty it will spin (unless it has been specifically designed to be curved for a particular device/model).
If you decide the battery is damaged, replace it with a manufacturer original or a respected third-party unit. In our experience though, third-party batteries are often cheaper but more trouble than they are worth, and can even be damaging to your device, so use one at your own risk.
Up against the wall
Charging from a wall socket is always going to charge faster than via PC or laptop. Likewise, the current is different, with a wall socket putting out potentially double the power of a laptop or computer. Of course, if you're using a different charger cable and adapter than the one the phone came with, it might also be the case that your charger is not sufficiently powerful for your device. For example, if you're using a charger that came with a Bluetooth headset, it may simply not have the guts to be able to charge your phone. There might also be a problem with your wall socket, but that is much less likely.
Update or rollback
Software updates and new Android versions can play havoc with your battery life, especially when upgrading an old device to current software. Newer devices are often optimized to take advantage of the latest software, packing bigger batteries and pre-optimized hardware, whereas your two-year old device can struggle when it makes the jump from behind the pack.
If this happens to you, consider rolling the device back to an earlier Android version, though be warned that this carries its own security risks. (The latest software versions are always recommended to keep your device protected, and while the risk of keeping your smartphone on an older version is often negligible, it’s worth noting all the same.)
Similarly, sometimes device battery life can be significantly improved thanks to an update, as seen with the Moto 360 smartwatch, so if you're way behind on your Android software version, head to the "about device" page in your settings and check for an update.
Switch it off
Using battery intensive apps/features while you are charging your device will affect how fast it gains battery life. If you are charging while Skyping somebody at full screen brightness, the device will naturally take longer to charge than if it is locked with Wi-Fi and 4G turned off. Better yet, switch the device onto airplane mode, or off completely, when you are charging if you want to see the fastest energy injection. Think of it as giving your device a power nap. Or a red bull. In the dark.
Calibrate your battery
Sometimes what your device “thinks” your battery life is, versus what it is in reality, can differ. The effect of this is that your phone may function differently based on the estimated battery life, like turning off before it is actually out of juice or taking an hour to chew through the last 2%.
We’ve already written an extensive guide on how to calibrate your smartphone battery on an Android device, so I won’t retype it all here, but this is a useful option to try before completely ditching your defunct power pack.
Try these steps on how to fix a phone that won't charge first before replacing the battery.
If all else fails, just double check that you actually have the power point switched on. That is the first thing they will ask you if you call your manufacturer for help, which might need to be your next step if none of these solutions have worked for you.
Have you suffered from a smartphone that won't charge properly? Let us know if you've found a fix that we haven't got.