that will work, as long as you do not want to work with it during charging time.
12v x 1.5A = 18 Watt – nah, you can even work with that while charging.
The most power I ever did draw with the 3s (14″ and plastic, rest mostly the same) was 18 Watt, it is normally between 6 and 12 Watt depending on the use and brightness.
So Yes, you are good to go with that solution.
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1981 soldered my first Sinclair computer 1K, tapedeck * 1984 build and sold IBM clones 8Mhz, 512K, 20MB HDD * 2018 messing with ultrabooks