I had to jump my 12v battery today - How do I maintain a healthy battery?

First I see what they say about the battery condition on Friday.
If they say the battery is good, that is "first lemon law criteria",

Next I let it sit for a week, if it dies, I take it in a second time.
If they say the battery is good, that is "second lemon law criteria",

If they get to "three service did not fix the problem before 24 months", I apply for arbitration under the Florida Lemon Law. Toyota can either buy the car back or replace it.

Perhaps a much bigger hassle than a hooking the $27 Noco charger every time I park and (hopefully) remembering to unplug the charger every time I go to use the vehicle, but if letting a $40k car sit for a week is not a normal use case for this Prius, my "Toyota Fan Boy" ticket is is going to be canceled. (I haven't had a 2nd choice vehicle for over 20 years, and after buying my 2009 Prius for under MSRP during the market crash, I didn't want a new car until the Gen5 Prius was revealed and then I had to have it. I still don't have a 2nd choice even with the warts, but "dies if you park it for a week" would really rock my world.)

 

all my gen2 and 3 prius sat unused for up to 3 months every winter in an unheated detached garage without problem

 

You assume an arbitration verdict will be won on a 12 volt battery though. I was trickle charging my gen 2, but not like I should have been. I put several batteries in it, wasn’t happy about it.
Today my 20 Prime charged the 12 volt to 100%, it was colder. i trickle charge it often, have a battery monitor to know when, and yes twice I drove with the charger connected. Just a few feet the noise starts. It helps to keep the mind more focused next time, which is more important as we age and start going zombie.
Get one of these, it is the best idea I got from this forum. My screen looks like the picture with two cars monitored. It also keeps a record for 5 days, very helpful to see what is actually going on overnight etc. Link not showing search battery monitor on Amazon, there is an Ancell for $24.

 

I should not need to understand this trickle charge stuff on a new state-of-the art car from the market leader and champion of reliability! Somewhere on this site is a poll where approx half of Prius 23 owners have problems with the 12V battery including me. Toyota ought to be taking an interest and making some proposals and otherwise someone will be sufficiently irritated to start legal proceedings and I might well contribute depending whether I EVER have to use my newly acquired Lithium Jump Start. This is not why I chose Toyota.

 

If you had a third gen you'd have much more stuff you "shouldn't have to do", lol. If the car companies were honorable, I'd agree with you.

 

It’s not just the Prius, other makes car forums are riled up about their 12 volts. I think we all know jumper cables are common now and in the past. In the past you could hear the starter motor start to turn slower as your battery aged or wasn’t getting enough charge during the winter especially. Then one morning it doesn’t start and you are looking for a jump. With a hybrid the idea is the same but no slow starter motor, it just doesn’t turn on one morning.

 

If you've got plain-Jane, old-school jumper cables, here a thought I've had, to keep yourself out of trouble:

Pull the two cables completely apart. Leave the black cable well out of reach.

Connect the red (pos) cable, at both ends. Make real sure both ends are on the batteries' positive posts.

Then go looking for the black (neg) cable, hook it up to the two negative battery posts.

(I'll always remember this one Scotty Kilmer episode, he's connected both pos and neg cable clamps to the donor battery, and he's wandering around with the other ends, pos clamp in one hand, neg in the other...)