What I found out the hard way, you'll need about 20 watts per headlamp
minimum or the transformer will overheat, couldn't find amp draw anywhere, I
know they are setup to handle up to 30 amps dc from a car battery, Just
played with it for about 2 weeks waiting for the stupid thing to overheat,
20 watts per bulb seems to work fine, that is with the round type lamp, the
halogens tend to pull a little more, played with them a little just didn't
like the brightness much. I am running 4 of them on an 80 watt supply for a
little over a year now, so far so good.