Bought a different charger now my tablet is taking to long to charge

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http://forums.androidcentral.com – I bought myself a Samsung Galaxy tab 2 10.1 but it didn't come with a charger. I have been charging it with the charger from my tab 2 7.0, but now that I sold it I bought a different charger for my 10.1 and now its taking long to charge is it because its not Samsung or because the volts don't configure the capacity of my table?... I don't know what to do and the place were I bought the charger wont give me the money back... only an exchange.. (HowTos)