a friend of mine ran 100w in his hellas, heat wasn't an issue. wiring is the more important aspect. chris I'd assume you could shine more light on that. you need higher gauge wiring and a fuse of some sort inline.
So long as heat isn't an issue, wiring isn't hard.
Throw out the stock wires coming off the lights. I think it's 22 gauge, which is just on the edge of not being enough for 100w.
Let's say a 100w bulb draws 9 A at operating voltage. I know it's a bit less, but let's be safe and say 9A.
IIRC, 22 gauge wire is only rated at 7A. so you'd melt it. So 18 off the lights. Now, 18 is only rated for about 16A. So you can't use that downstreem of the lights or you'll melt the wiring. ie. if you wire 16 from two lights to battery. You'll melt it.
You're going to want to use 14 gauge or bigger wire between the lights and battery. None of this can run on stock car wiring unless you want to set your car on fire. Or just keep burning fuses. Use a good quality 30A+ relay straight to the battery, use the stock wiring to turn the relay on and off.
Then a 25A fuse right off the battery into the relay. You could possibly get away with a 20A fuse, but that's just on the edge of being enough.
Even though 16 gauge wire, rated for 22A would technically be enough between the lights and battery. That's 4A above what you need. But this would necessitate using a 20A fuse. You can't use a 25A fuse because that's rated at more than the wiring. This means the wiring would catch on fire before the fuse blew. In reality, it would probably be fine. but on paper it's bad. So you need to use a heavier wire than your fuse.
Besides, running wire at close to it's maximum rating means the wire runs warm, degrades faster, has more voltage drop, etc. no reason not to run a size or two bigger than you need.
Now, since you've just added so much extra current draw, you really need to make sure the ground between the body of the car and the battery is up to snuff. It may not have been a problem before, but if it's a bad ground you might start pulling a lot of amperage through the grounds in electronics. This isn't cool at all. So just check the body to battery ground, clean the terminals, make sure it isn't corroded, etc.
Also, with the lights on, check the voltage drop between the pos bat terminal and the pos alt terminal. If there's more than 1/2 volt drop or something make sure that path is good too.
