mgbrillo.. para saan ba yang "relay"?
sir mali po ang "interpretation" ng relay...a relay is used so that the your battery can be connected to the lights directly. The relay functions as a switch...a more reliable switch than the switch inside your car.

The switch inside the car can get burned kasi if you put high amperage of electric current dun. The relay controls that.

However, the relay does not control the burn-out of your bulb. A burn out could be caused by very high current drain. Bulbs are like wound up na wire. They burn when current passes it....too much current will "over-burn" it.

Maybe you should have a fuse on that line (dapat meron fuse talaga yan, but I think you did not mention that). So if too much current na ang dumadaloy, the fuse gets busted and not the bulb. The fuse is cheaper than the bulb.

my 2 cents.