Hurricane - 12v power supply question(s)

Possible hurricane in the area in the next few days, just got my 110g set back up recently. My question is in regards to how long I can run certain things off a 12v power inverter.
 
How long can a Eheim 2080 Canister Filter rated at 20 watts/hour run on a standard 12v 'car/marine' battery?
 
Still building the tank up, so only 2 corals, not too worried about a few days without the lights. I have Koralia as well but figure I would leave that off and just use the main filter, get circulation and filtration. I also have the JBJ 500w true temp heater/controller but I figure with out temps in the mid 70's as it is the tank should not have any issues holding a decent temp.
 
I would be open to answers or website links that could help answer my question. Thanks!
 
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