After fitting a Varta G14 to my vehicle 3 days ago, the battery will not charge at more than 12.2V regardless of light or heavy electrical load. A multi-stage charger only gets the battery to 12.5V after a little while which then quickly drops to 12.2V so it looks as though the battery has failed rather than not suitable for these vehicles. The IIDtool function to indicate that a new battery has been fitted was done today, in fact twice, with no improvement.

Any comments?

Edit - false alarm. Wriggling the battery monitor connector caused proper charging at 14.6V for a run-down AGM. Having reconnected the charger for a longer period and seeing the voltage now rising, it was appropriate to check the monitor connection.

Where is the battery monitor connector? Is it the small snap on to the battery negative pole?

Click image to enlarge

Yes.