How many watt invertor can I use safely on the 12v battery

Hello all,

I want to use an invertor for my prius C. Unlike my previous cars, the 12V battery is a lot smaller and has a lot lower capacity.

However, it does have a traction battery charging it when in ready mode.

If I use an invertor, will it be tapping into the 12V battery or will it be taking from the system that is charging the 12V battery, thereby sparing the 12V battery discharge.

And being a smaller battery, what's the maximum wattage invertor I can use without damaging the battery. I definitely don't want to shorten the life of the battery or damage it.

Thanks.