nazeem:
Can we hack the conventional mobile charger its input is 220v/110v and output is 5v by tinkering diodes is it correct.
If you have a 110V/220V AC switched-mode 5V power supply you may be able to use it.
In a switched-mode AC power supply the 110V/220V AC is first turned into DC at a fairly high voltage. You may be able to apply your 72VDC to the AC pins and have 5V come out. If it doesn't work one way, try swapping + and -.