Xenon HID start-up circuits actually ramp
up to the peak (say 18A in your case) for about 3 secs then fall off to half of the peak about 5 secs later then almost linearly fall off to the steady-state run current
for the next 15 sec or so. You, therefore, will not experience a full 180A load that entire time, only for about a second. Regardless, you need to plan out the wiring
to take off from a battery
directly and not go through a distribution panel serving other needs.