Sorry, the Syntax was wrong, I wasn’t using the option which allow me to leave out the useless threshold fields.
Here is the good syntax : echo "P output_voltage voltage=${voltage};185:;150: (In this case : lower than 150 = CRIT, between 185 and 150 = WARN, upper than 185 = OK )
Now I can adapt it to others services, Thank you a lot guys !