I am with Spanner Juggler on this.
In order to prevent the battery going completely flat, I invested in a CTek 0.8 charger last Autumn in case we had a stiff Winter (30 quid approx. from Halfords )
However, I understand you cannot use this version if the battery is dead/almost dead - it needs a higher spec.
I have mains in the garage, so putting the charger on overnight after more than a few days without use, and it is fully charged by the next morning.
Happiness is a fully charged battery!
