The battery guy came and replaced my battery today.

After fitting the new one he ran a voltage check when I started the car.

He said helthy charge is 14.5v

When I fired it up it was reading 15.3v. He said that would fry the new battery, then after 5 minutes it suddenly fell to 13.5 volts and remained there.

Is this a normal part of the computer controlled alternator behaviour to supply higher votage for 5 minutes during warm up?

 

Everything you just described is perfectly normal..!

 

mojorising, yes, the computer plays a lot of games with the alternator on start up. What you are describing is just fine. It gives the battery a little boost right after start up to try and replace anything that was lost during the starting of the car. Smile and be happy.

 

I'd smile and be happy if I just had a "battery guy" come to me when I needed a battery replaced. Nice!