Is your iPad not charging as well or as fast as it used to? If you have an iPhone and an iPad it is possible that you have somehow gotten the chargers MIXED UP and you are using the 5W charger to recharge your iPad.
The older iPad charger is 10W and and the standard iPhone charger is 5W (the iPad 4 has a 12w charger). Look closely at the print on the bottom of the plug that came with your Apple device and check to make sure you are using the correct one.
The 10W charger (old iPad charger) or 12W charger (new iPad charger) can charge both your iPhone and the iPad. The 5W iPhone charger will charge the iPad but at about 50% slower. So check again if you may have possibly got these 2 chargers mixed up.
The iPad Mini comes with the 5w charger and takes around 3.5 hours to charge from completely dead to 100%. When you use the higher wattage charger it charges faster. Use the 12w iPad 4 charger and you can charge the iPad Mini from 0-100% in about 2.5 hours. That is 25% quicker. If you use a higher wattage charger it may make your battery life shrink in the long run but it shouldn’t hurt to use a 10w or the 12w charger occasionally on your iPad Mini.