http://www.instructables.com/id/Auto-Power-Off-Save-Batteries/%3Famp_page%3Dtrue&ved=2ahUKEwiWrZz3mI_YAhUK5WMKHVQiCaYQFjAEegQIABAB&usg=AOvVaw3q6R8SqXAbyQJLYrOnVK5C&cf=1
Ckt describes microcontroller as the timing device to shutoff power. S/w to resume pwr.