Is my 12v battery dying? A/C settings getting lost and 14.7 volts..

best way to test the 12v is at the jump point under the hood in the morning before starting the car. if it's 12.5 or better, you're fine. but replacing a 7 year old battery prophylactically isn't a bad idea.

no idea what's going on with you're a/c setting, that is an odd one.

 

But if you cover a battery in rubber, it won’t work!

Seriously, I know that the battery voltage is over 12V. It’s a good idea to replace at the first sign of gremlins, or else the car won’t start and you’ll be stranded somewhere.

If you don’t buy Toyota’s, Optima Yellow Top is the replacement battery most people go with.

 

12.0 Volts is roughly half discharged.
"over" 12 volts isn't good enough.

And I don't agree with your conclusion about " most people".
Optima doesn't have a really good reputation for reliability.

Seems like a lot of owners have good luck at Pep Boys.

 

That AC Delco is compatible, it says NBCI S46B24R, which is the right buzzword. They are showing the wrong picture. (the battery in the picture is a 18 month battery)
the correct picture is here:
www.amazon.com/ACDelco-ACDB24R-Advantage-Automotive-Battery/dp/B010GKJ8F6

 

My 12V battery is at 14.7-14.8V all the time while the car is on. I would not use that as an indication the battery is failing. If it is, my battery has been failing since at least 5 years.
Did other settings go to default as well? Radio stations being forgotten?

 

When the car is "ON", you are not measuring the battery voltage but the charging system voltage.
That tells you virtually nothing about the battery itself.

 

First time I’ve heard that. They were first to have a Prius replacement battery, loads of Prius owners used them, and I never heard a complaint about them until now. But I don’t particularly care; I don’t work for them and if you’ve really experienced this I’ll take your word for it.

 

Sometime around 2015, they had about 6 months to a year of a high initial failure rate; would only last about 6 months.
That has been reported here.....several times.
I don't remember seeing any complaints lately though......so I have no good data on how they last now.

I DO have a problem with their marketing claims however.
Whenever any company says that their product is orders of magnitude better than anything else IN THE WHOLE WORLD......I tend not to believe that.

 

Optima was purchased by another maker and after that they stop manufacturing the spiral battery design & implemented ways to cut cost including quality of products, when that happened their reputation became average so it was a good company at one point.

 

That sounds quite good for your hot southern weather. While batteries with 84 or 96 month warranties (limited or restricted, never full replacement for that long) are available, the factory battery certainly doesn't fit that bill.

The high voltage is not simply a matter of higher internal resistance. The charging system does adjust its set voltage according to the charge level it thinks is on the battery, starting at higher voltage when the charge is low, then stepping down when the charge is better. If your regulator never steps down on longer trips, that suggests the battery's age is showing. (Short trips may not be able to keep even a good battery charged well enough, Prii seem to have an issue with this.)

My system voltage on a long trip today (on a battery just a couple months old) was just 13.5 V, i.e. well charged.

 

14.7v when lights are on or transmission is in Park, or battery temperature sensor is cold, and for a few minutes after startup. Otherwise, about 13.6v. How long the aforementioned few minutes take depends on temperature.