if the laptop runs longer (with the psu disconnected) on the old battery when charged, than on the new battery when charged, it suggests the new battery is duff.
Contact the supplier to arrange its return.
A new battery sometimes need quite a while to fully charge first time.
A replacement battery should supply the same volts and same (or preferably higher) wattage than the one it is replacing.
Please advise back on progress.
Good Luck - Keep us posted.