Okay. Who HASN'T had a 12V battery issue with their 2023-24 Prime?

Much more expensive BMWs, Audis, Mercedeses, etc. are a lot worse in 12-V-battery longevity than Gen 4 and Gen 5 Priuses and Prius Primes.

Again, there is no problem with the Prius battery 99% of the time—you only need to observe certain precautions. The main two things are (1) to use a battery maintainer at least once if the car has any history of not being driven for more than a week in order to bring the battery SOC back to a level maintainable by the car’s native charging system and reduce the sulfation and (2) not to have a persistent habit of leaving the car plugged in for longer than overnight.

 

Exactly, you must use a battery maintainer after everytime the car has been sitting for longer than one week, as the car’s native charging system is not capable of fully charging or healing batteries with a low SOC.

 

My guess is that the 12-V-system operation during solar charging is very similar to that during AC charging.

This means that the DC–DC converter is on (possibly at a low voltage such as 12.92 V, albeit reportedly higher in Gen 5) during traction-battery charging and turns off when the traction-battery reaches 100% SOC. So, once the traction-battery is at 100% SOC, the parasitic drain on the 12-V battery will increase due to the charging computer still being on but the DC–DC converter being off.

This brings an interesting question: Do the vehicles with a solar roof have a higher parasitic drain on the 12-V battery, as they must constantly monitor the status of the solar roof?