Flashing battery light

This afternoon I had to have my hazard lights on for about 20 mins. I was parked with the engine switched off and after about 15 minutes I noticed the battery light flashing in between the hazards flashing. I've never noticed this before, the car started ok soon afterwards, drove ok/smoothly. Anyone got any ideas please. It's a 2011 207 1.6HDi

 

Even with the key in, Peugeots still like to go into 'eco mode' after about 20 mins- turning off supply to radio etc to conserve battery. The battery symbol flashes to show its in the eco mode (I guess in case the main screen is turned off). Once you restart the car, the eco mode is reset. The eco mode doesn't effect your hazard lights so its just co-incidental that they blink at the same rate. Even with a new battery it will do the eco mode function- its not necessarily any indicator of battery health.