General rule on 12V battery life

Hey, I got the year right!

 

By accident I found a way to get an early warning of a dying 12 V battery. Basically turn the car to IG ON, not READY. More here:
Early warning sign of a dying 12 V battery | PriusChat

 

I replaced 12V batteries in both my Prii pre-emptively at six years with no problems preceding replacement, so I think a six year replacement interval is reasonable for the OEM but I am hoping for more from the optima yellow tops.

It should be pointed out that rather than automatically replacing at a time threshold you can boot into diagnostic mode and look at the "vehicle signal check" which is the 12V line voltage. If it is 12.3 or higher with nothing on and above 11.5 with the headlights on in accessory mode, it is probably still fine and replacing it is likely a waste of money. If it is below 12.0 with nothing on, and drops below 11.4 with headlights turned on, then replace it. If you have any symptoms that could be explained by a bad battery and the voltage is less than 12.3 with just the single press of the power button then replace it, but be aware that the coolant pump may run for a bit when you get in and place a demand on the battery so wait a moment to give the voltage a chance to come back up.

What is the lowest voltage anyone has seen without symptoms, and what is the highest voltage anyone has seen with symptoms? I've seen 12.0 resting and 11.3 under load with no apparent issues.

To access diagnostic mode, hit the power button once with foot off the brake. After the boot up screen, hold display, then on the touch screen two invisible buttons can be pressed in the top left and bottom left of the screen, just above and below the lines that appear due to holding the menu button. Press up, down, up, down, up, down, then let go of the display button. Then press menu. Once you check voltage with everything else off, you can hit power again to enter accessory mode and check voltage under loadwith the fans and lights on. If you turn the car on (power with foot on brake) it shows a voltage of 13.8 or higher that is the charging voltage, and tells you nothing about your battery really. At that point you can hold the info button to return to normal ready mode. Testing should be performed after the car has sat overnight after a long drive.

 

??

The Toyota TrueStart battery that I have seen for Prius is made by GS Yuasa in Japan and has TrueStart stickers applied to the top and side. The GS Yuasa stickers are also still visible.

Does your battery have an 84 month warranty? That is a benefit of the TrueStart brand.

 

OK, if you have a Prius w/o Smart Entry/Smart Start then it would use the shorter battery, and maybe Toyota has not gotten around to calling that one a TrueStart.

See dorunron's photo of the GS Yuasa/TrueStart battery he recently bought for his 2G with SE/SS, prior to trading-in that vehicle, in post #16 above, in this thread. That battery was made in Japan.

 

yes, not so much in the earlier gen II's, but later, and definitely gen III, they cheaped out somewhere along the way. they must have decided it was a good place to cut costs and still have reasonable reliability.

 

Yes, 9 years is old age for the battery.

Who's "they"? In Canada, with a local sale, you're obligated to pay a core charge, refunded when you bring in the old one. It encourages responsible recycling.

 

I must have low expectations, I'm very happy with a battery that has an 84 month pro-rated warranty. IIRC I paid ~ 180 USD at the dealership, so I'm locked in to a $2/month plan.

Let's see ...
I drive about 10k miles a year, so the 12v is adding 18,000/70,000 = 0.26 cents a mile to my maintenance costs once the new car battery needs replacement. I'll call that half the life of the vehicle, so the 12v adds 0.13 cents/mile to lifelong maintenance costs. Oh dear

OP: I bring my old battery to Walmart, but I bet any oil shop would take it.

 

i thought they were required to accept them here. maybe it's a state law?

 

yes, but i think this is a response to massive failures and one year warranty previously.

 

Doesn't feel very "north" right now. Some BC locations broke high temp records today. Dan Global Warming.

 

I believe that anyone selling batteries in the US is REQUIRED to take back the old ones for recycling.......at no additional charge (already built into the price).

 

I’ve been checking the condition of the original 12V battery in our 2008 more frequently over the past two years. It’s been fairly stable (voltage above 12.0V) during that time but over the past several months I've noticed it dipping slightly below 12.0V on occasion. Then, about a week ago, I was moving the car out of the garage and when I pressed the power button, I noticed that the red triangle warning symbol stayed on a few seconds longer than normal. When I stopped in the driveway and shut down, the red triangle stayed lit along with intermittent beeping sounds and the car did not shut off completely. Another press of the button shut everything down but the beeping remained even after I opened the door.

I checked the MFD diagnostic page and found the 12V battery at about 9.7V! My wife is the primary driver of our '08 (I drive a '13) and over the past month, she's been making several short trips daily (1-3 miles) instead of the usual distances. I reasoned that these repeated, short trips might have prevented the 12V from fully charging. I asked her if she had noticed any strange behavior in the days prior and she said no.

At this point, I put the car in ready mode and allowed the 12V to charge up for a while, which it did. However, checking it again over the next few days showed that it could not maintain a charge above about 11.5V. The most obvious sign that this battery was rapidly fading was that I could only enter the MFD diagnostics without any other load on the battery. For instance, if I turned the parking lights on or even just stepped on the brake pedal (brake lights on) during diagnostics, those loads were too much and the MFD would immediately shut off and re-boot. Clearly, the voltage could not be maintained with even a light load on the battery. Normally, one can turn on the headlights, press the brakes, etc. in diagnostic mode to see how much the voltage drops due to load. Definitely time to replace this battery! I called a few local parts stores but replacement batteries were all around $180 (Los Angeles) plus tax. So, I ordered the Optima Yellow Top online for $147 and it was delivered two days later with a 12.7V full charge. Already primed on the replacement instructions (service manual pages and YouTube) I installed the Optima without any issue in about 45 minutes.

So, add my story to the archive of “strange and unusual behavior” that precedes the inevitable replacement of the 12V battery. Considering how critical the 12V battery is to the operation of the Prius, it's a wonder that Toyota doesn't have the car flash a warning message (a simple "12V battery low" would suffice) if the battery condition is marginal for proper operation. I guess we just have to be satisfied to "listen" for the Prius' equivalent of a slow-cranking battery on conventional cars!

 

Your car is 6 years old. I have had the mindset that I am going to put a new battery in my car when it is 4 years old whether it needs it or not. Good peace of mind for me.

 

Since you have been going to the trouble of checking battery voltage from time to time, what prevents you from hooking up a battery charger overnight when you see that the voltage is below 12.6V?