Sorry about the confusion, the LED will light up when the voltage hits 16.8v and will stay on till it reaches 24v.

Hi

When it reaches 24v does it stay on or off?
Your answer will have an impact on complexity. If it should turn off, then the circuit will need a window comparator. If it should stay on, then it will not.

eT

 

When it reaches 24v it will go off as the LED would be reverse biased. That is idea. The hysteresis is set with R2.