What are you using it to charge? The included adapter and cable or your computer? Are you trying to use it while it's charging?
I have to charge my tablet from a 2AMP wall power plug and a good cable. If I use my pc, USB on a PC only puts out 500millamps, and my tablet seems to consume about 600milliamps just sitting there on, so it won't even charge as fast as the power is being used unless I power it fully off then charge from my PC.