Battery change 156 1.6 T.Spark
The battery in my 51 plate 156 is flat. I jump started it and drove for 40 minutes, then parked up. About half an hour later, the battery had insufficient power to turn the engine over, though all of the dashboard lights, etc were bright and clear. On trying to start the engine, these lights went out and returned once I let go of the key.
The alternator warning light is not illuminating when the engine's running, so I assume the battery is not taking a charge.
Are there any tricks or special procedures I need to be aware of before I swap it out for a new one?
Just as an aside, the engine management light came on earlier this week and stayed on for a few days but went out. A diagnostic check showed "knock sensor". This may have been contaminated/condensated fuel as I have been running it close to empty on a few occasions.