Safe use of Coiled Cable
The hazard with coiled power cables is they can't dissipate heat as effectively because it's exposed to less air.

It's especially an issue for long cables since some layers of the spool are exposed to no air at all, instead being surrounded by more hot wire.

Fortunately 3 meters is not very long, and you will not need a very tight coil to take up that length. So I'd say a safe guess would be:


Coil it loosely, so there is only one layer of coiling.
Derate the the maximum current by 50%. This will be a 4x reduction in heat generated, since power is proportional to the square of current. So be sure the attached equipment will not draw more than 2.5 amps. To really be sure of that, add a circuit breaker or fuse.
Be sure there is ample airflow around the cable. Don't coil it inside a small cabinet or in a wall, for example.


Of course I can't take responsibility if this starts a fire anyway. The cable will get warm before it catches fire, so if after running the equipment for a while you notice the cable getting noticeably warm, it's probably time for a thicker cable, or a shorter one that doesn't need to be coiled.