My mom's 2006 convertible just started a mysterious battery drain. With the Covid crap the last couple of years it doesn't get driven much as my 85 yo mother's friends are scared of exposure. So, we replaced the old battery with a new one as it was about 4 years old. We tested the alternator and it's charging as it should. We then went through every circuit with an Amp Hound and everything tested zero draw. When you hook up the battery there's a definite big draw as it sparks pretty good. I thought we would find it with the Amp Hound, but no, so now I'm stumped. Any ideas?

Thanks,
Frank