Ac generator

plan to add an ac generator as ac input to hybrid inverter - battery charger. Some inverter specs say they can take ac generator as input some say they cannot. What specific add on circuit is needed to allow connecting ac gen to hybrid inverter to charge batteries when grid is down and pv covered with snow…? Or what is the difference between hybrid inverter which accept ac gen and the ones which cannot accept ?

I would NEVER connect an AC generator to a regular hybrid inverter as the system can export solar energy to the generator - This will blow it up and cause irreversible damage.

What you need is a dedicated off-grid hybrid inverter that has a generator/grid AC input and can be programmed to operate with a generator. Here is a list of some of the most popular hybrid inverter-chargers which can be connected to a generator