My missus car battery keeps going flat - it isn't the alternator as this is showing 14v when the engine is running across the terminals. Anyway long story short I have bought a battery off the internet and was going to fit it at the weekend. I have tried googling but to no avail - if I just disconnect the old battery, put the new one in place and hook it up will it mess with the alarm and immobiliser? It is an 04 plated ford so not some super duper new car. Not a Focus either! I know the radio presets will be lost and I have the radio code so that isn't problem.

Any help will be appreciated.