Don't forget to check the inline maxi-fuse between the battery and the alternator. It is back against the firewall. On the V6 you need to pull the coil pack for access.
A fully changed batter (with surface charge removed) should read close to 12.5 volts with the engine off. With the engine running you should see something over 14 volts, ideally with a fully chaged battery and the engine reved up to about 2000 rpm with no electrical accessories on you should see 14.2 volts.
You may have a defective new alternator.
