[jk1981]

what happens if the voltage generated buy the generator is less then pack voltage?

say for example i have a max pack voltage of 150 and the generator can only produce 144, and i turn on the generator before the pack has dropped bellow 144v.

In its simplest ICE-generator_set form the ICE will run unloaded, assuming the throttle is open sufficiently its RPM will either rise until generator output minus rectifier drop is above pack voltage, the rev limiter kicks in or something flies apart with a bang. Getting it to run efficiently will realistically require a closed control loop of some sort.