I'm considering replacing a 300W / 500W R7 halogen fitting with one of those 12v HID car fittings, (and obviously customising the halogen lamp housing) I'm also trying to do it on a budget. I'm looking to change five video lights.
I COULD buy a large lead acid battery of about 28AH, (bulb has inrush of 10A, but working current of around 3.5A @ 12v, so batt could last 7 - 8hrs) but ideally, I would prefer to work with 240V.
So my next idea - and the one that I'm a little concerned about - would be to use a 240V to 12V power supply, such as a PC PSU or similar. Since most items are SMPSU these days, I'm wondering if the output would 'collapse', (ie not even start up) if it's suddenly asked to provide 12v @ 10A to ignite the bulb at the onset. (If it was asked to provide 12v@ (say) 1A at startup, it could possibly build up a reserve in the output cap/inductor to supply more current at a later stage, but to jump straight to 10A ....)
It also seems to be a lot of 'work' electronically, converting 240v to 12v, and then 12v through ballast to control lamp. I've found a few 240v to HID ballasts ... but then read that the "ballast must be matched to a particular bulb"
Anyone worked with these lamps? I'm doing this to a) reduce heat of lamp as I've read that HID run cooler than 500W halogen, and b) get more light output for less current.