I have a draw that kills my battery overnight. I went out today to test it and found some weird goings on. I disconnected the negative cable then attached a light between the post and the cable. The light didn't come on. Weird thing #1. So then I started the car and while trying to check the voltage, my meter was jumping all over the place without even touching the probes to the battery. When I would get the meter anywhere near the engine while running the meter would jump around. I made a video showing what I'm talking about but it won't let me post it.
https://youtu.be/ALUx_4nvKS8?si=QRKW4-WYPeaR38hH