My 1999 Audi A4 has been parked for 3 months, and the battery is completely dead. I would like to be able to charge it up, so what is the best way to do it? I have a trickle charger.

The battery is in the car and remains connected.

Some questions:

Is the 1999 Audi A4 positively or negatively grounded? (ie, should I connect the negative terminal of the charger to the negative battery post, and the positive terminal of the charger to the engine body, or the other way around?)

I can't see whether the fluids are low and if I should add distilled water to the battery, nor figure out how to open up the battery. The manual states that the battery case is opaque, but my case is black, so I suspect it has been replaced. The number on the battery is 000 915 105 AF.

What else do I need to know?

Thank you!

 

An update, since there have been zero replies.

Somewhere in the Audi manual that came with the car, it said to attach the charger cables directly to both battery posts, instead of one cable grounded to the body. So I went ahead and trickle charged the battery at 2A for 2 days. Perhaps not surprisingly, the car still wouldn't start, so this morning I disconnected the battery from the car and will start charging at 10A. Hopefully I won't have to pull the battery out as it's such in an inconvenient location at the back of the engine with all sorts of plastic and stuff in the way and it looks damn heavy.

I still couldn't figure out how to open the battery cells up so I couldn't add any distilled water, so I'm thinking it might be a maintenance free battery? The battery number is 000 915 105 AF.