Charging battery in car?

[Roberto]

The Legnum has been sadly sat on the drive for far to long now.

Currently she is ticking away on the drive way after being jumped by the Astra.
The battery was as dead as a Dodo.

Charging voltage is at 13.8v and the AirCon is being ran on and off.

But anyone any idea how long it could take to bring the battery back to life?
It is a fairly new battery ( about 2 years )

[Kryton]

Might be worth digging out your paperwork if only a couple of years old as the last 2 batteries I bought came with 5 year guarantees.

[Roberto]

After a little bit of reving, a whole lot of idleing with and without air con.

Decided after 3 hours to see how she was, battery charging voltage had dropped to 13.6.

And has stayed there since, so one recovered battery for the sake of a bit of petrol.