Aspire cf maxx battery not charging like normal

I have had this cf maxx and mega tank which until last night would charge in 2-3 hours now it's been on charge for over 6 hours an still it's not charging as it should what could be the problem.

Only got it on 30/4/15. Should not be failing now. It's only Just over 4 months old.

Any help on what to do would be good.
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