It might work if you have nothing much connected to the USB and drawing power. 1.5A is below the 2A minimum recommended for a Pi3B (Pi PSU is 2.5A, Pi3B+ has that as its minimum recommended supply).
You will need good (thick, short) wires from battery to Pi. Off charge, it will last about an hour. There is no indication about whether it can supply power while charging -- the input spec suggests not.
"Thanks for saving my life." See https://www.raspberrypi.org/forums/viewtopic.php?p=1327656#p1327656
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