R8 flat battery

[hosedoctor]

Sorry if this been posted before guys,went to start the other halfs R8 today and the battery is dead! First question,is this a common thing after sitting for a while? And secondly what's the best battery charger/ maintanence? Thanks

[hosedoctor]

4-6 weeks? I had a maintenance charger plugged into the cigarette lighter but not sure what's happened?

[hosedoctor]

Ahh that would make sense,the car is a 2015. Thanks for the help.