Yes it was a linear voltage regulator - LD33CV or LD1117AV33.
The Vin max (on the spec sheet) is 15V.
I kindly suggest to use a step-down converter instead of a linear voltage regulator 
Going down with a LVR from 12 to 3V means 75% of the energy in the accu is dissipated in the LVR, meaning 75% goes out in the air as heat. The efficiency is then 25%.
A step-down or buck converter has a much higher efficiency.
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