Electrical Issue regarding Low RPM's

I have followed @pacificmeister guide on electrical equipment. I have a 18.5 volt Lipo 5 cell battery connected to a seaKing 130 Amp ESC powering a SSS 56104 500 KV 6 pole brushless motor. When running at full throttle I measured measured voltage across all phases which all read at 13 volts. ( Online the motor specs says up to 88 volts) It doesn’t appear the RPMs are remotely close to @pacificmeister first motor test in his Part 6 video. Any help is much appreciated, ready to hit the water!

running 5S? i think you more like 12S: 43-50V to get some rpm, try to put 2 battery in serial (10s)

-this is the video I was referring to. He uses 1 battery and achieves a lot of power.

-this is the battery I’m testing. I have 2 but I’m using one at the moment until I figure out why its not getting enough RPM’s.

When I connect the two batteries in series it blew up My UBEC.

Ubec has to be for 12s , calibration 100% on the remote thorttle on start with the esc ( pairing) and 100% power selected on the esc parameter ( with card or software ) ?