[BrendanP]

Can anyone tell me what the recommended output voltage should be and does it have to be measured at a specific RPM? The cars I'm interested in are a 2011 1.6 CRDi without stop/start, and a 2015 CRDi with stop/start and AGM battery. Does the output voltage vary according to the type of battery?

[Lorian]

Since 2009 they've been using smart alternators on UK cars to the voltage varies based on a number of factors (Battery state, temp headlights, rpm over-run etc)

[sundiz]

AGM voltage is little big higher when compared to normal lead acid battery. But generally speaking the charging voltage should be over 12V when at idle. With revs the voltage should be around 14V. Shut down all the electrics you can from the car. Lights, radio etc. before measurement.

I have one smartcharger which uses 14.4V for normal battery and 14.7V for AGM.