Why is 12 V replacement battery so expensive?

Yes it WAS. Many of the numbers above are low enough to indicate a battery close to complete failure.
12.0 is a bit BELOW half discharged and a healthy battery should not go that low.

But if you like adventures.............

 

A feller once posted in here with his 12v batt measuring 11.7v for many years, and said no issues. He did prefer not to mention the climate of car driven in and battery age.

Still waiting for someone to jump a prius with 18v drill battery.

 

Prius 12 volt battery is the most discussed post on this site has been since I became a member in 2006.

here’s the best take away. If you own a Prius of any generation buy yourself a good quality voltmeter and learn how to use it.
I recommend a fluke for at least $100
It will last a lifetime and if you know how to use it will save you countless hours of time And $ both in your car and home.
For a Prius owner of any generation find out where the front under hood jump point is and measure the 12 volt dc voltage there with car off after taking a nice long ride.
A g2 For instance with a very good battery lives at 12.6 volts with car off with car on the charging voltage ranges between 13.5 to 14.2 on a g2.
Find out what your car reads trust me it will come in very very handy down the road.

And never ever measure the dc battery voltage at the battery itself always at the front jump point. Toyota made it very easy for you to maintain the 12 volt battery and never have to touch it. They do not want you in the hatch. Never ever jump the battery directly to the battery in the trunk.

Periodic maintenance charging is very healthy for the 12 volt battery And can extend the life of the battery for years via the front jump point but that’s another discussion.
Lastly people on this site who have repeated 12 volt battery failures all have one bad habit
They do not arm the alarm every single time they get out of the car because if they did it would not allow you to arm the car if lights or door ajar were left on especially in the garage with kids.
Kids can’t get in the car if it’s locked and armed. They will always leave the door ajar after playing in the car.

 

@Georgina Rudkus

 

Anybody that has owned a Prius for 6 or 7 years has probably spent less on maintenance than any other car they have ever owned. Why play brinkmanship with a aged battery? But a new one and rest at ease!

 

Absolutely, positively NOT necessary.

While I'm not a fan of a lot of the electrical parts that they sell, the little red multi-meter from Harbor Freight
is more than adequate for automotive testing.

At about $10 each, I have one at home and one in each vehicle. That leaves me about $60 to buy replacements should one fail.
None has so far.

And if you want something that is a bit more versatile and looks nicer, you can get one at any auto parts store for about $40.
Big box hardware stores too.

This reminds me that it is time to check the batteries in all my meters.
I almost had one fail when the battery corroded.

 

A quick Reader's Digest version would be helpful.

Guilty! I have my Prius set up to have absolutely no lights come on when the door opens (even unplugged the puddle lights) for stealth reasons. I've learned the hard way that an ajar door, even with no lights, will kill the battery. Unfortunately, I seem to keep learning that lesson.

 

Haven't left a door or hatch slightly open draining the 12v completely yet. If I had kids and they did that, child adoption agencies will sure hear from me.

 

I still have the OEM 12V battery in my 2013 Prius. This thread inspired me to check my battery ASAP. I checked only a few measuring points above.
Before 1st use: 12.54 V
Opening the door with FOB key on hand: 12.30 V
Press Start Button 1st time Radio on: 12.19 V
Press Start Button 2nd time: 11.99 V

Results are convincing enough the battery needs replacement soon. Hey, it was a long ride.

 

I think 7 years is a good run.
I think many start having trouble about that age.

 

The ol “bathtub curve” is a good statistical measuring tool for battery life expectancy.

 

Yes but.............
That diagram is USELESS unless it is based on actual collected data AND the "time" line has actual units shown on it.

 

The illustration is just a statistical concept. And yes, there is no data applied. The upward trend at the end of life cycle graphically shows a sharp decline in reliability. Let’s pretend that the time line is about 7yrs.

 

Or you can just take all the guess work out of it and purchase an electronic load tester so you can check your battery (or batteries if your family has multiple cars) whenever you want. Personally, I have an OTC 3183 model, but there are many available that are even less expensive like a Solar BA5, Schumacher BT-175.

I can't even guess how many hundreds of times I've used this thing. Family, friends, coworkers, customers. No guesswork, no opinions, no 'I think', it just provides facts...........

 

What do we pretend for the y-axis to be?

The spelling “Ageing” makes this graph much credible.

 

While both "ageing" and "aging" are accepted as correct spelling, the former is more prevalent in the UK, the latter in the US.

 

I replaced the battery today with a Toyota 84 month one for $200. No more battery worries for now .

 

one year after i replaced my 2012's with the same thing, amazing!