Hi HksHopper,
I'd say it's exactly as BVH suggests. I have several Power On Board 35w HID's. With fully charged stock 7ah batteries, the voltage drops from 13v to 12.1 volts at startup. It may rise to about 12.3v once warmed up, but if the battery was starting to go bad or is just old, the example I state here could be drastically worse.
Those Harbor Freight HID's may have been sitting for a long time. It may be better off removing your battery and testing it with say one for a car. Just do some temporary wiring to connect another battery to the lights battery terminals and you'll know immediately if it's a weak battery or something else. Please post your results. Good luck.