This is my second battery for my 2024 Prius

this is an ongoing problem for many gen 5 owners with no solution offered by Toyota.
the design is draining too much when the car is off.
is there someplace you can plug in a battery maintainer when not driving?

 

I suspect that your doing very short hops in your car or the dealership is mishandling their batteries.
Starting the car causes a strain on the battery, so a "short hop", less than 15 minutes of driving, may not put back enough power into your battery to get you back even. Slowly chipping away at your battery levels.
The dealership could've placed bad or not fully charged replacement battery into your car. New batteries are shipped partially charged and if staff is lazy and drops the battery, they can damage them. Don't know if auto parts stores up there will do free battery checks. I would probably have an independent shop test it. If it's bad, have the dealership replace it again - then go back to the independent shop to verify if you have a good or borderline replacement battery. Your dealership could've just recharged your bad battery the last couple of times and had claimed to replace it. Did you look or mark your old battery to validate what they actually did???

Good Luck....

Also check for dealer installed anti-thief devices installed for insurance purposes. They tend to malfunction and draw down your battery. They usually piggy-back off of your OBD2 power wire connection. Trace back that wire from your OBD2 socket. If you find that barnacle, remove it.

 

You can try storing your key fobs in a metal box to ensure that the car is able to completely shut down.

Also, PHEV Priuses should be unplugged once fully charged.

The other solution is to periodically unplug the 12 volt battery sensor on the negative terminal. This forces the car to charge the battery at 14.3 volts in “Ready” mode and doesn’t result in any warning lights. I have been doing this for a couple of days about once a month. With the sensor connected the car charging logic is very stingy, typically leaving the battery only about 50% charged.

 

Even in winter? The sensor has a temperature sensor. On my non-plug in '26, I haven't seen less than 14.3 volts at the OBDC adapter. Perhaps in summer, which can't get here soon enough. Stop sending us that cold Canadian air! Heck it's snowing!

 

Roughly extending the voltage line, it looks like mine would take about a week of inactivity to get to 12v. This is in an unheated garage, maybe around freezing.