HowardHouse

My daughters Audi A1 has been sitting on the drive for 2 months whilst she has been away. The battery is flat, and despite trickle charging it for over 3 hours the message still comes up, "turn off ignition, Battery is discharging" and it will not start - not even a sign that the starter motor is turning.

Bob Petruska

First this is the Q5 forum.

What year A1?

How old is the battery?

It's also going to take a more than a trickle charger to charge up a completely dead battery in 3 hours. A good standard charger may take 10 -16 hours to fully charge a very dead battery. The battery may be so dead
that it never recovers.

Redd

If a car battery, especially a conventional battery, has actually gone totally dead, it may not be save-able ever again. With some batteries they can be brought back to life 4-6 times, yes. But if they go totally dead and SIT that way for any length of time? The sulphates which form become permanent, and you can't bring them back to life. So a lot depends on just how long it sat and what the previous history was.

Be careful. "New" chargers will sense a dead battery, below ~10.5 volts, and simply NOT TURN ON and not charge it. Older chargers will try to charge it--but if you try to charge a dead battery, you can make it explode, and acid in the eyes and all over the engine bay is not a good thing. A dumb charger that will charge it at a 2-6 amp range, for a total of some 50-75 amp hours, is a reasonably good way to see if it can be charged at all.