I've mentioned using fused relays for QI (Quartz-Iodine) lamps before, but the caution is worth repeating.
Make sure you use a fuse link in all QI lighting systems!
For some reason, BMW tends to fuse the low-beam circuits, but not the highs. (On pre- '72 BMWs neither circuit is fused.)
Buy an in-line fuse holder (about seventy-five cents including a 20-amp fuse) and install it in the high-beam line. If the lamp element does not conduct properly, it can effectively produce a "dead short" to ground.
The lamp wiring then heats up, exactly like an electric resistance heater, melting the vinyl insulation. It is even possible to start an electric fire this way. The "ounce of prevention" is very cheap.
I'll be glad to answer any questions on the particular procedure to use on your year and model BMW.
Author: Bence Boelskevy