If it is the original battery it might need replacing Andrew, but don`t spend money if you don`t have to, so take it out-weather permitting- for 45 mins each day and watch it swap energy with the Hybrid Battery on the screen
If the weather does not permit, then start it up and sit in the drivers seat for 30/45 mins daily and watch the interchange of energy.You can read the paper,or magazier or the Handbook to pass the time. Do not put the radio/cd on. The engine should switch itself on and off whilst you are sitting there solving all of the problems of our World. Please report back in due course.