How long does the battery last without driving?

That’s a good question that can give you a lot of answers but let’s think it’s a battery that it’s installed and not unplugged from the car, first what’s the SOC when you park the car, 50% 75% 100%? and what is the capacity remaining of the battery, so I don’t think we can have a straight answer for that, I believe you will learn you car and you will know after you learn you car how long it can keep it charge, I personal think they should last 30 days at minimum, but that’s only my opinion and reality change and get shorter with the years.

 

The aux battery:

1. In average mid-life condition (3-4 years old), I wouldn't expect it to last more than 3 weeks before it needed a charge. Potentially it would be weak enough to not boot the car's electronics.
2. Add a week for each year newer than that.
3. Take off a week for every year older.
4. Add about 30-40%+ to the time if you disable the SKS function using the button under the steering wheel.
   
5. This is merely based on my experience with having 5 Gen 2s parked in my driveway, with some not moving for several weeks at a time.

As for the HV battery, it all depends on it's condition. Every battery has some self discharge. As it gets older and more miles, the individual modules will diverge from full capacity and some will start having higher self discharge issues. Some may take a week, a month or more. Some may take days or hours. Some may self discharge a 'significant' amount just by the car sitting overnight, resulting in only one or two pink bars on the display when you get in the car the next morning, even though you know it had 6 purple bars when you parked it. This is a well documented symptom that an HV battery will be coding soon.

If your HV battery is original but not showing any signs like above, I would be comfortable leaving the car alone for a week at a time without firing it up for a drive or force charge. I wouldn't go longer than that, but it depends on what I saw. You probably want to initially check it every couple days to see where the bars are when you power it up. The batteries I have in my cars have all been built by myself. I'm ok with leaving them as-is for months at a time. I've never had one code out, regardless of how long I've let it sit. A brand new HV battery from Toyota can sit on a shelf for 2+ years and still be at 50% SOC. That's speaking from experience.

 

there's no good answer. take it out at least once a week for a good long drive under varied conditions, or be prepared to replace both

 

This is exactly what I mean when I said in my post #2 you get to know you car and then you get to know how long it take to discharge the battery.