Thanks, I haven't bought anything as yet so just wondering if its possible or if I need to have the lights plugged in overnight rather. This is idea is more to save on electricity so I may get a solar panel or 2 to charge it during the day, maybe use 2 batteries instead.105Ah at 12V = 1.26 KWh.
Is it a deep cycle battery? If not, the usable capacity is probably 20% of that, 50 if it's deep cycle.
So best case 600Wh.
So your 100W load would deplete the battery in 6 hours - less if the inverter's overhead is not included in the 100W figure.