Okay. Who HASN'T had a 12V battery issue with their 2023-24 Prime?

What about those of us with non-Prime HEV models? My 12V drains quickly. After driving, it never charges to above 12.35. Then in 2 days of sitting it will be down to 12.06 or so. First scheduled maintenance will be in July. Hopefully they'll have a solution.

 

Has your dealer installed a tracker?

 

I had some serious issues, but nothing since I installed a battery maintainer. I was unable to start the car once, while leaving it parked overnight at a hotel. Since then I've carried an extension cord and made sure to plug in the maintainer overnight.

I also have an auxiliary battery, like on a camper. It fits nicely into the space near the left rear fender. It's connected to the main 12V battery through a VSR isolator, which prevents the auxiliary battery draining when parked. The Voltage Sensitive Relay (VSR) cuts in at 13.3 volts and cuts out at 12.8 volts to ensure the primary battery is always charged and ready to start the vehicle.

If the auxiliary battery goes dead from running the drink cooler overnight, it only takes less than an hour to charge it up again through the isolator connection. I have also rigged a heavy duty bypass switch around the isolator, with a 30 amp fuse, in case I need to "boost" the primary battery. So far, the bypass current has never exceeded 10 amps.

 

having to keep a maintainer on it is a real plug for toyota engineering

 

I went on travel for exactly two weeks and when I returned from our flight the battery was too low to start the car. Unfortunately it never gave me a clear indication of why it wouldn't start, so I kept trying until the battery was well and truly dead. I find it very unreasonable that an otherwise regularly driven and maintained new car can't sit in a long-term parking lot for two weeks in moderate temperatures and humidity without draining completely. In my mind, that's a serious design or engineering flaw.

 

Which point for the -negative connection did you end up using?

 

There's a youtube channel based in Japan that did some reporting on the rear door issue. As it happens, the channel also posted a recent video on what I assume is the 12v battery issue. I'm relying on the auto-translate, so if there's a Japanese speaker on the forum, maybe they can have a listen?

The translation refers to the battery as the auxiliary battery, which I assume is the 12v. The channel believes a recall will happen for this issue at some point.

Apparently the 2 middle cells of the battery are getting damaged. They could be getting damaged simply via the installation of the battery in the car...something about a protrusion in the Prius that is impacting the battery? Or maybe the cells are just defective. Anyhow, it's interesting to see someone based in Japan also reporting on this issue.

 

@Salamander_King is fluent in Japanese.

 

Hi. Newer member here and eagerly awaiting a 2024 Prius Prime due to arrive early next month. Been following this battery issue here. I watched the whole video with auto-translate on and I think the auto-translate also said the damage referred to led to "leaking of the battery" somehow and actually caused rust in his car along with the car not able to start anymore due to the weak battery. In auto-translating the comments, it seems he said he knows of two cases of "fluid leaks".

It will be helpful if someone can better translate all of it.

 

Checked the video. The summary by @Yvrdriver is right on. But there really isn't anything technical that he is discussing. I did not dig deeper, but sounds like he works at a Toyota dealership, But his opinion on "recall" on the failing 12v battery seems to be based on just 2 incidence he knows at his shop. In both cases, the 12v battery was cracked and leaked. He is speculating that may be due to manufacturing defect of the battery or the installation problem, but without any evidence to support it.

So, all in all, I take it as just another YouTuber blowing air without much substance. I have noticed the "12v battery" problem in almost any modern car forum. My current drive Escape PHEV has a thread on it that is now 14 pages long. People report problem and some had replaced the 12v battery under warranty two, three times. In most cases replacing the small OEM lead-acid battery to a bigger AGM battery solved the problem for many. But the fact it does not happen to every one, means there are some user case variable that affects the longevity of the 12v battery. Mine is now 18 month old, and so far no problem. I think in many cases, it is an operator error, such as keeping the car in "ACC" mode too long with high wattage items such as AC on that causes the initial drain on the 12v battery, when this situation is aggravated with low frequency short drives, the small OEM 12v battery just do not last long. This is not uniquely Gen5 Prius problem. That's just my 2 cents.

 

The HHR had its 12V replaced under warranty while still in my father's possession; bad cell. Defects happen, and even low incidences will seem like a lot when millions are made.

 

doesn't sound like the problem most owners are having. the affected cars are draining the battery too quickly when off and unplugged, from what i have read

 

From Chrysler owners manual about 1998.
I don’t know how Gokhan managed six weeks, but he did.
VEHICLE STORAGE
If you are leaving your vehicle dormant for more than 21
days you may want to take steps to protect your battery.
You may do the following:
• Remove the 20 Amp mini-fuse in the Integrated Power
Module labeled Ignition-Off Draw (IOD).
• Or, disconnect the negative cable from the battery

 

the beginning of the end

 

i regularly left my 2012 prius unattended for 2 months in winter (unheated attached garage)
but then, the 12v only lasted 6 years

 

The self discharge rate for batteries slows down as they get cold. It's why old carbon-zinc ones needed to be stored in the fridge.

 

but it's not self discharge, the car is always using the battery when off.

 

The battery doesn't stop self discharging when hooked up. They would die over time back when there were no electronics or features always putting a load on the battery.

As for vampire draws, the biggest one on past models was likely the SKS. Closed off in a garage, there is going to be less events like people walking by that trigger the system to search for a fob.

 

It is almost always an operator error.

I left my 2021 Prius Prime Limited with a full active Toyota Connect subscription for over six weeks in a hot a garage last summer, and the 12-V battery was as strong as as it could when I came back.

 

There is definitely something wrong with some gen 5’s