Re: 18v ?? what can I use? help
Such a hard question to answer. What are you looking for? Probably balance of runtime, brightness, beamshape, heat, cost...
Since each 5W is supposed to be the equivalent of 4 1W, your second configuration would be brighter. But realise that the 5W also consumes twice the current as a 1W, so the equivalent power consumption would be 2 parallel rows of 5x1W. This should then be brighter since it would be 10x1W instead of the equivalent 8.
2 rows of 5x1W LS with a 1ohm resistor should also be more efficient than 2x5W with 5.5ohm resistor. This is intuitive. There is less voltage drop across the 1 ohm resistor and hence more going to the LED, where it would be more useful.
The downsides would be the cost of buying so many LS LEDs, since although the 5W output is the equivalent of 4 1Ws, it is not lliterally 4 times the price of the 1W. Also, you need more space to mount them and the beam shape would probably be wider, even if you did fit them all with NX05 lenses (which adds to the cost).
Another worry is the heat generated. 1W run at the spec of 350mA would produce a negligable amount of heat, but the 5W would produce a fair amount of heat even when powered to spec. This heat would need to be disapated, which would be difficult if the host body were plastic.
Another consideration, but that probably wouldn't make much difference since you probably won't be leaving it on for extended periods each day, is that the 5W lifespan is rated for 5000 hours (about as much as a regular household halogen bulb) whereas 1W is still rated at 100,000 hours (or 50,000 in more conservative estimates).
Ultimately, it is your choice with compromises all round. Best of luck with your mod.
