I’m pretty sure my roommate’s car is suffering from the parasitic drain problem, but Subaru says it’s not. Here’s the summary of what’s been going on for the last year.

My roommate works from home for her main job, but she also does home health care (Registered Nurse). She’s only had one patient for the last year, and she drives an hour and a half round trip every other week to see her. Otherwise, she drives her car for errands. Her car can sometimes sit for a week or two, but this isn’t often. Don’t know if this matters, but it has less than 20,000 miles on it. But as a comparison, my 2021 Wrangler also has less than 20k miles. I mention this because of an experiment we did that I explain further down.

A year ago her battery died. We thought she may have left lights on, etc. I jump it, she drives to her patient, comes back. Two days later after no driving, it’s dead. We replace the battery with the exact same type. A week of no driving, and it’s dead. Jump it, drive around for a while on the interstate, come home. A few days later it’s dead.

Go to Subaru. They say the battery was installed wrong. Not parasitic. Fixed now. Week later it’s dead. So starts the cycle of jumping it and it dying soon after.

We experimented. I left my car (2021 Jeep Wrangler) without driving it for two weeks. She drove everywhere for errands and friend gatherings. My Jeep starts fine. Leave it another two weeks. Jeep starts fine. Outback sits for less than a week and is dead.

I have a battery tender for my bike that we put on hers last week after jumping her car and her going to her patients, so the hour and a half round trip. I know this wouldn’t be enough to charge it all the way up, so I was curious how long it would take my tender to get to green. It took about 9 hours.

Does this sound like parasitic battery or is she just not driving it enough? If it is parasitic, how do we convince Subaru? I say we because car stuff is not her forte (but she does keep up with maintenance like clockwork). Subaru says they tested it for the drain issue and it was negative. If it’s her needing to drive it more, that’s easier to fix.

Thank you in advance for any advice.