Discovery 4 16v at idle

Hi all,

I have a 2010 discovery 4 3ltr
So I have had to replace my old alternator and fitted a new alternator last night, I have checked the battery at idle and it is sitting at 16.2v across the battery.

Is a new alternator likely to be bad and need replacing of is there something else going on here I should be checking for?

I have checked the battery when the car is off and it is sitting at 13.6v

Any help would be great!

What make was the new alternator? I think Denso are the one to get.
Is the battery shagged? ie cooked by the old alternator.

Plus 1 and also wonder if the BMS module was reset when the new battery was fitted using diagnostics and if the replacement battery was a lead acid or agm

Funny enough heard more and more about different makes of alternators being fitted and causing all sorts of issues when denso alternators haven’t been fitted