Rechargeble battery?

i bought a digital camera two days ago
the salesman told me to recharge the battery for 16 hrs
which i did but one battery did not get charged i got it replaced
the new set of batteries charged once but after using for few shots on battery became almost dead ( i checked using a multimeter)
wht shd i do ??

I would take it back to the salesman and ask for a replacement.