12v in the front

it'll probably be very similar to the sealed AGM units in the older generations. But the engine heat might be a bit more harmful to their longevity overall

 

Does the vehicle warns you in advance that the 12V needs to be changed soon? If not, what's the symptoms to look for (beside a car not turning on)?

 

There is usually not a lot of warning, an indicator for me to change a battery is usually when a lot of corrosion/acid materials start forming on the battery terminals.. If you're worried about battery failure, you should change it every 5 years or so. Some may even fail before that time, and some will last longer. But that is usually a good timeframe for a Prius 12v battery

 

it is not a 'standard battery' in terms of size, it is still difficult to find and expensive.

it is a conventional battery though.

 

Get a charger and digital voltmeter and charge the bat whenever you won’t use the car for a while. A good charger will give you some indication when the battery is shot.

 

Yes, it a standard, wet cell lead-acid battery. Not AGM. I don't believe there's any difference in lifespan. I'm still using the original battery in my 2016 Hybrid, now 7 years old. Here's the spec,

 

As far as a warning that it is going to fail you could buy a simple battery tester (preferably one that indicates Internal Resistance) and spend about 2 minutes every once in awhile to test it.

 

The car should have that logic built-in and warn you when it detects the 12V battery needs to be replaced soon.

 

that would be a great feature!