In November I bought a new Micra off the showroom floor and was told they needed to replace the battery as the car wouldn't start. They also claimed the other Micra on the lot suffered from the same issue. I noticed that the hatch light didn't always shut off when closing it which was difficult to see in the day as it's slightly obstructed. I suggested to them that this was what was causing their batteries to drain down and to adjusted the hatch to allow a tighter fit. They took it in the bay and adjusted the hatch latch which then solved the problem. So, just an FYI in case anyone is suffering from a battery losing power, this is something to look for. Cheers!