12v small battery is at 12.7v and is 10 years old! Miracle battery?

mine expired after 8 years.

i would get a free load test at an auto parts store. one day it was 12.7, and the next day, after it wouldn't start four miles from home, it was 4.4v, and i'm not in punta gorda.

but i did abuse mine, leaving it sit every winter for a couple months

 

I just replaced my Prius-C's OEM battery after 10 years. Yes, the battery can last 10 years.

 

Only thing a 12v Prius battery does is turn the computers on and flip some relays that turns the high voltage battery, which then powers everything while recharging 12v. So there's lots of people that buy a defective 12v for their Prius and go years without knowing it.

I got 9 years out a 55amp-hour mobility 12v. They only cost $100 and have more capacity than the garbage ones auto parts stores sell for $300. Here's the one I currently help sell: https://ebay.us/5n8222

 

Has your mpg dropped? If not, you're ok. But should start saving for one.
I replaced mine a few months back, and that's what it was reading. Then one day,
it wouldn't ready the car. I had to use my jumper. 2 hour ride home, it started the next day.
But later in the day, it wouldn't. I put it on the charger overnight. It started the car.
But after that, I need the jumper. So I replaced it.

If you carry a jumper pack, at least you won't get stranded.

 

^This. Voltage is helpful to check, but doesn't tell the whole story. There's a new breed of load testers, little electronic gizmos you clamp directly to the battery posts, enter some stats (rated CCA (Cold Crank Amps) and battery style), push a button and it'll tell you the tested CCA, voltage, and a verdict.

I'm using a Solar BA5; current itteration is BA9 I believe. You can get them for around $60 USD

The stores with testers typically have a pro-level tester of the same ilk, more heavy-duty, capable of printing out the result.

 

My 2012 PIP 12v battery just passed the 10 year mark two months ago.
Left it idle for almost two weeks last month but started right up.

Mike

 

As long as you don't accidentally discharge it badly, the 12-volt battery in a 3rd-genration Prius has a much easier life that of a conventional car. It never has to crank the engine, and lives in a relatively cool spot