12 V. battery drain issues on 2016 prius

if you hit the park button, the car is still 'ready'. that means the engine, hybrid battery and inverter are all working together to keep the 12v charged.
here's what to do:
1) go to an auto parts store foe a free 12v load test, to see if it is healthy.
2) charge it up or replace as necessary
3) with the car off, measure the draw on the 12v to see if it is within spec. if it isn't, you're gonna be spending a lot of time learning how to chase down electrical goblins.
if it is, then you're just not driving enough, and you should keep it on a 12v maintainer when not in use.
4) or you could just keep it on a maintainer and avoid the hassle

 

Newer cars with keyless entry and start buttons will drain a battery. It's always scanning; look for your FOB. A few weeks without driving or recharging that small old battery will mean a dead car. The Prius in particular will run readiness diagnostics at certain intervals; powered by the 12V battery ONLY!

Get the 12V battery load tested to see if it needs replacement.

Good Luck..

 

Your protracted downtimes are very detrimental to the battery.

that’s good. It’ll likely need a replacement battery though; the current one likely too far gone.

 

I press the park button most of the time, but it only requires the start stop button to be pressed to turn off the car. I often sit for a few minutes in park watching my battery monitor charge level for the 12 volt.
If 12 volt is too low like 70% or under I put a battery charger on the 12 v. without a battery monitor it's flying blind. Amazon has them, like Ancel BM200 for $24.

 

I rarely if ever push the Park button, due to convenience of it happening in conjunction with hitting the Power button (shutting off).

that said, more times than I care to admit, I’ve JUST about exited the car, still in Ready (fully on), and in D (drive), just held by parking brake.

I think the old-school key-in ignition and conventional shifter were light years ahead in this regard.

 

WHY are you pressing the Park button? If you are shutting the car down, press the Power button and exit the car (just like the Owners Manual tells you to). IF You press the Park button and exit your car, your car will sound an alarm to tell you “you forgot to turn me off”. So, first you are adding an additional and unnecessary step, and then ignoring the alarm that is telling you to shut the car off the correct way.

 

I sometimes use park at long traffic lights, or if I want to talk on the phone before exiting the car etc. In park, the 12 volt charges.
It depends what the battery monitor is showing. Last night the 12 v was in the 70%’s, and I could read the resting volts wasn’t that high the 24 hours before, so I put the charger on. Monitor I have holds 5 days of data to review. It also tells me what my charger does, the way it charges.

 

I can understand that, and think it’s a great idea.
My comment was directed at the OP who seemed to be saying that the OP makes a habit of placing the car in Park, then pushing the Power button, as a normal shut down procedure (like shifting to park and shutting off the key). If that is true, then the OP doesn’t understand what the Power button does (ie: places the vehicle in Park as part of the shut down function).