Engine Start Battery

yours is proof that prius like to be driven. i also have a 2012, but only 60k. no issues, and i keep an eye on the battery with a volt meter, instead of worrying about when i might need to replace it.

our 12v experiences seem to be unusual however, as most here seem to only get 4-6 years.
the key to success imo, is never letting the battery drain. that shortens the life span dramatically.

my last two prius 12v lasted 8 and 10 years. it is said that warmer climes are harder on battery life.

 

I think most forum members would say if your battery is 7 years old, it's time for replacement. If you decide to risk driving it a little longer without a new 12V and wait until it starts to give you problems, at the very least you should carry a jump kit somewhere in the passenger compartment. It should be one that has a chip that senses polarity before it allows current to pass to your battery. This will prevent damage to your inverter that could result from having someone jump start your car incorrectly. It should be carried in the passenger compartment so that if the car fails to unlock using your remote due to the 12V being too weak, you can use the physical key to open the door and then connect the jump kit to the correct jump points under the hood, rather than having to crawl through the car to reach the jump kit in the luggage compartment. You could perform a load test on the battery to be sure that it needs replacement, but at this point it would probably fail. If you continue to drive with a weak 12V, with the added security of having a jump kit with you, be aware that your MPG will suffer and the car may show misleading warning lights from time to time. The problem with constantly seeing warning lights on your dash is that you will never know when you have a real problem. I understand your compulsion to try to get the last bit of life out of the resources you have. It is commendable from the point of view of trying to preserve your finances and the environment, but maybe it's better to just let the 12V go.

Congratulations on caring for your car well enough to get 429k km and 7 years out of the 12V.

 

Spring for something like Solar BA5, see where you stand.

That's unreal kms btw. have you ever cleaned the EGR, intake manifold?

 

I had 8.5 years on our 2010’s battery when I swapped it out at the beginning of 2018.

They do last if you don’t discharge them.

 

Are predicting the future, Ray, or doing some time travelling?

 

He’s from the future

 

Sorry, should have been 2018.

I use an iPhone 5s and the keyboard leaves something to be desired when you type with your thumbs.

Amended above.

 

Are there any signs before it finally drains and you can't start the engine?

I have a 2010 and previous owner changed the battery in 2014. Per Toyota service records, previous owner tried to start the car but couldn't and had it towed it.

I want to prevent that from happening to me and take care of it right away.

 

There are plenty of signs the 12V is dying, including warning lights on the dash (typically the ABS and VSC lights, but be aware that they may appear for other problems as well), difficulty unlocking doors and weak headlights when the car is not in the Ready mode, but why play a guessing game? Buy a Multi-Meter for $10 to $20 and check the voltage of the battery at the jump points under the hood. You should see a voltage of 12.5V or better when the battery is at rest. (Open the hood, lock the car, move the key out of proximity range, and then measure the voltage after a few hours). Better yet, get a jump kit as I suggested to the OP in #3. For less than the cost of a tow or a diagnosis at the Toyota dealer, you can have the peace of mind that you will not need a tow for a dead 12V. Additionally, you can safely help out a friend by using the kit to jump start their car, if that's what they need, something that should never be attempted from the battery on your Prius.

 

Test it with something like a Solar BA5. It'll measure the voltage, the Cold Cranking Amps (or Cranking Amps, or a few others), and give a verdict on it's health. They're around $50~60.

 

I had to double check my service history but it looks like we replaced the 12v with about 7 years on it (purchased the car new in 2010.)

I had to jump it (used a jump pack) one very snowy morning so I had the dealer put in a new Panasonic-Toyota OEM. A bit more money than if I had done it myself, but I was recovering from a long surgery debacle still and it was really cold and snowy so the extra $$$ was worth it.

We get good life out of our car batteries here in the cold/temperate climate. I replaced the 12v in my 2005 4Runner last winter, it was the original equipment Panasonic.

 

I have 2010 Prius III. (Manufactured 07/2009, First use 08/2009). The original battery died past June (2018) with no prior warning or symptoms(The car just wouldn't power on). So that makes it almost 9 years. And all of this is in Florida heat. I guess the reason they last much longer is because they only power electronic devices and some small electric motors (electric window, cabin fan etc.) No excessive power demand as starter motors require. Thus they last till they have very little power left in them.
I don't replace vehicle batteries under preventative maintenance while they are still working fine. They get replaced when they die. And the thought of "I might get stranded someday somewhere..." doesn't bother me. Because it can happen for many other reasons.

 

I think a faltering battery can impact mpg, the hybrid battery has to devote more and more juice to keep it going?

 

That could be a viable theory. The best is to perform a load test as you suggested. Voltmeter will not be reliable.

 

There's lots of anecdotal evidence that a weak 12v can cause all kinds of wonky issues with a Prius including intermittent warning lights and odd behaviors. It may not have a lot of power, but it does key a bunch of electronics and a weak signal there can cause issues.