Would a 80 watt solar panel be able to charge a 12 Volt Battery?
Look at it this way,
A 12 volt car battery that has 600 amp-hours of current storage has supposedly 7200 watts of power available (12v x 600 amp=7200 watts)
But in reality you would be lucky to get a third of that.
Anyway, if you run a 40 watt light bulb for say 10 hours you used 400 watts of power from that battery. Your solar panel in the middle of a sunny day might put out that 80 watts and when it does, it will take 5 hours to charge back that 400 watts of usage for that 40 watt light bulb.
So your 80 watt panel will place 80 watts of power back into your battery every hour. Of course if it is cloudy or early/late sun you might get as low as 5 watts an hour.
So it’s just a balance equation, you have to calculate the total amount of watts your appliances and lights use per hour and calculate on average your panel is going to put around 50 watts per hour for about 12 hours a day ( about 600 watt-hr)