Prius Prime lithium- and lead–acid-battery drain during storage

We’re the doors locked and SmartKey active?
I’d be curious how depleted the 12v was.

 

I did something similar in 2018 when the car was a year old. Went on a 60 day cruise with the traction battery fully charged, but put a battery tender on the 12V battery. I wanted to see how much charge the traction battery would lose, so I just checked the mileage available on the HUD before I left and when I came back. It was a negligible change; about .2 miles if I remember correctly. After that, I learned from this forum to never park it for a long time with the traction battery fully charged. I know checking the HUD mileage available isn't very scientific, but it was gratifying that it didn't lose much charge in two months.

 

My solar roof equipped EU Prime, when left parked outside, takes care of the 12V and charges the traction battery up to 80% in around a week, depending on the starting point SOC, the season and sun exposition.
80% SOC is equivalent to 54 km of extimated EV range being the maximum extimated EV range in the summer around 67 km.
I guess then that such SOC value is considered safe by the OEM for the traction battery health.

 

Don't leave your car plugged in when you go away for vacation. It'll drain your 12 volt battery. If that battery is old, it'll drain it enough so the car won't start.

 

Unfortunately there’s a good chance your 12 voltle drain if you leave it unattended for a long period. The real solution is to leave it unplugged and put a battery tender/trickle charger on the 12 volt battery when you’re away.