Car key has red light lit

Hello all

My car key (for a 02 reg Megane) has on a couple of occasions recently had the red light on it lit up - both times when I've first picked up the keys to go out in the morning. The light seems to go out when I use the key to remotely unlock the car - then stays out.

Is this a warning ? Is there a battery in the key - I've wondered if it's a low battery indication ?

Any advice would be appreciated

Thanks

Adrian Featherstone