How is a flat battery caused ?

There are many reasons why a battery can go flat.

A flat battery is often the result of numerous short trips during which the battery is unable to be fully recharged. However, during these journeys, energy consumers such as headlights, rear window defrosting, and the multimedia system are used.
Even when the vehicle is parked, it will draw current from “silent” consumers, such as the on-board computer, alarm system, and other electronic components. If the vehicle is stationary for an extended period, the battery may no longer be able to supply enough power to start the engine.
If the vehicle is parked outdoors, temperature changes and weather conditions can also accelerate this process.

We recommend the vehicle is run for around 20 minutes a week to recharge the battery.
Please note: this also applies to electric vehicles, which have their own 12V battery in addition to their high-voltage battery.