I've gotr a 52 plate (Jan 03) Focus 2.0 zetec. 130K miles so it's old an tired...

The battery has been fully discharged and recharged at least once (I did it by leaving the parking lights on overnight) but that was a few years ago now. It seems to be getting flaky of late and this afternoon it wouldn't start at all - all the needles flicker up and down and the dash lights flicker on and off.

I put the battery on a charger but it indicates it's now fully charged less than 30 minutes later which seems too quick if it was discharged fully.

As the car is old I guess it could be the battery is just getting old and needs replacing or the alternator might be on it's way out? Or could it be worse and something like a bad/shorted wire?

I know it's vague, any ideas though?

Thanks,