At full tilt it probably drew 40 amps or so not much by today's standards. Confirm your battery is good, then pull one side of all the non-essential fuses (heater blower, wipers, radio, etc.), if it sits and makes it a few days ( or keep an on eye on battery level if you have it with you) you know the culprits and can start to individually bring them back online until you find the problem circuit. Running the circuits down individually won't be fun if the above doesn't work.
M&P-10+AAC Cyclone - Kel-Tec RFB+Griffin Sportsman Ultra Light 300
ATN OTS 336-50mm 9hz Thermal Monocular
ATN NVM14 NV Monocular