r/prius • • Sep 24 '25

Discussion Toyota/Lexus Hybrid 12v Battery Failures - Analysis of Charging Issues - Deep Dive Analysis & Workaround

68 Upvotes

Hi all,

Below is an analysis I have been conducting over the past year regarding 12v battery failures in Toyota and Lexus hybrids, which I'm finally ready to share with various Reddit communities.

It goes into the reasons why the batteries appear to be failing more often with extensive data that I have captured myself and gathered online from others also having issues.

12v Battery Failures - Analysis of Charging Issues - Deep Dive Analysis & Workaround - Google Doc

Most importantly, there is a workaround fix that anyone is free to try.

I have included how to do this in the document for anyone that feels comfortable enough to use it (at your risk). I've made sure to try and answer any questions about that too.

I'd welcome any other input/questions from people who have had their own issues with this. I'm hoping that enough chatter will get Toyota/Lexus to look into and issue a fix for this problem.

At the very least I hope this is useful to someone.

Thanks


r/prius • • Aug 12 '26

News Hiroshi Okuda, Toyota Chief Who Pushed For the Prius, Dies

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679 Upvotes

RIP legend


r/prius • • 9h ago

Pic/Video Filled every bit of interior space + 580L roof bag filled with vacuum sealed bags of clothing, 2 adult bikes + 1 baby bike. Then drove 2000km.

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48 Upvotes

At one point (day 2 of trip) it got kind of hot and suddenly wasn't accelerating, several lights indicating overheating; I stopped on the side of the road, let it sit for a couple minutes and fired it back up and drove a bit slower. Honestly I was driving too fast for the amount of weight. It's a 2010 with about 210,000 km.


r/prius • • 3h ago

Buying/Selling Advice Would you get a refurbished ($1.5k) or brand new ($3k) hybrid battery? 116k miles, Prius C (2014)

9 Upvotes

So somehow, my hybrid battery is depleted much earlier than I thought it would be. I went to my longtime family mechanic, who told me that a brand new hybrid battery is going to cost roughly $3k. However, he recommended I get a refurbished hybrid battery instead as that only costs around $1.5k. He said that as long as I don’t drive “long distances” the refurbished battery should perform almost identically to a brand new one.

My current daily commute is about 30-40 minutes to university and back home. That’s less than 20 miles a day. I don’t take my car far that often. I stay local. However, within the next year or two, I may be attending another university farther from home (about 10-20 extra miles give or take, I’m not sure yet)

So I’m a little stumped on what I should do.

My car is 12 years old. The more I drive it, the more maintenance needs it’ll have with mileage increase and such. Is it even worth it to drop $3k on a brand new battery with this in mind? Will I be putting more into this car than is worth it as it continues to age?

What would you do in my situation?


r/prius • • 2h ago

Pic/Video Front bumper

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5 Upvotes

Anyone know which front bumper this is


r/prius • • 7h ago

Question Can I take a Prius to the great outdoors or camping?

6 Upvotes

Hi, with gas these years, with toyotas reputation, I think I got a fixation on getting a Prius, but I've wanted to explore the great outdoors, and want to start outdoor hobbies of backpacking, car camping, hiking, and snowboarding. Can these hobbies be done with a Prius? I found a used 2013 one with 170k miles for barely $8k (including all hidden fees and taxes), and I'm wondering that even though a Prius obviously isn't a jeep or an SUV (cannot afford a good SUV hybrid RN) if it is still feasible to have a Prius as my main vehicle and do these hobbies.


r/prius • • 3h ago

Pic/Video How bad is this?

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2 Upvotes

Mechanic thinks it’s not worth fixing.
This is a 2007 with a 4 year old replacement battery.


r/prius • • 1d ago

Pic/Video Learned 2 lessons today

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112 Upvotes

Just bought this big Joe bean bag from someone hoping it would be a perfect fit for my living space. When I saw it, I almost knew it wasn’t gonna fit my living space, but I had hopes! Anyways, I learned this HUGE 7FT bean bag actually fit inside my car (with some finesse)!! Got it in the house and lesson 2 is that this is way too big 😭😭

This was inside a 2017 Toyota Prius 3 Touring.


r/prius • • 2h ago

Mechanical Help Red key light on dashboard

0 Upvotes

My 09 Prius has a red blinking key light when the car is off. Changed the key fob battery tried to do reset etc but nothing works any suggestions on how to get it to go away? Just happened one day never went away


r/prius • • 8h ago

Buying/Selling Advice New 2027 LE, Dealership Talked Down from 33k to 31.5k - do I buy?

2 Upvotes

Hello all!

I’m in the market for a new car, and my old Toyota Versa is about out of life. Because of my long commute, I’ve narrowed my search to Hybrids, and because Toyota is reputable for their reliability, I’ve landed on getting a newer Prius LE.

Because of the state of the used car market, I think it makes sense for this to be my first new car purchase. Right now, my issue is supply. I’m in the outskirts of Houston, and looking within a 250 mile range from me, there are only 2 2027 Prius LE’s near me or even scheduled to arrive anytime soon.

One is being sold way too high, and the other I negotiated down to $31.5k, which from what am reading is 1k over what others are buying. Most 2026 models I found near me are used, and are somehow listed above that amount!

My deadline is end of year for when I need this. Supply looks extremely low in my area, don’t know if I should pull the trigger or if I should continue to be patient and expect more to come in over this year that I can nab at a better deal.


r/prius • • 10h ago

Mechanical Help Engine replacement

3 Upvotes

I have a 2016 Toyota Prius with 120k miles. I took it in for low coolant & intermittent coolant warning. They diagnosed it and did a drain & fill. About 3 weeks later it was blowing white smoke out of the exhaust, said it needed an engine replacement. I strongly believe there was already a head gasket issue when I brought the car in originally that went undiagnosed, potentially leading to further engine damage. Any thoughts on this?
NOTE: no warning lights when the white smoke started blowing, my car felt like it was driving totally normal


r/prius • • 23h ago

Question Gen 2 Prius repair cost

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26 Upvotes

Purchased my first car yesterday woo! 75k miles 2005 Prius for 3.9k off marketplace. I paid a mobile mechanic for a pre purchase inspection and he went through a checklist and told me it was a decent deal, so I didn’t haggle as the seller was a disabled senior citizen. I brought it in to a shop today and was gutted to realize the mistake of not getting it on a lift pre purchase. Ive been riding public transportation for over 3 months now, and since I was ready to drop 12k on a newer Prius I didn’t fight but I am curious. Did I get hosed 2 days in a row or is the shop offering a fair price for the work? Location is San Diego


r/prius • • 5h ago

Mechanical Help 2007 prius been sitting 6 years

1 Upvotes

I am wanting to get a 2007 prius running again, ive already acquired a good hybrid battery and my 12 volt battery is good. I have not checked the fuel yet but what is the best way to get old fuel out? It probably only had about 2 or 3 gallons since there only one block showing on the fuel guage. Any help is appreciated


r/prius • • 6h ago

Mechanical Help Anyone know how to remove these fasteners? They are on the side of the vehicle for the plastic tray. Have some sand and gravel I need to get out. 2016 Toyota Prius Two

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1 Upvotes

r/prius • • 11h ago

Mechanical Help broke a sensor’s wires, which one is it and am i screwed?

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2 Upvotes

pulled the dipstick tube too far to the right while changing my head gasket and the wires broke. which sensor is this, and is it an easy fix?

(2010 prius, 210,000 miles)


r/prius • • 12h ago

Mechanical Help Update: p0aa6 code.

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2 Upvotes

After a few weeks working on tracking down where the isolation fault was. I found it to be in the transmission. Draining the fluid confirmed, purple and burnt. Swapped a 09 transmission in. Found a weak number 10 pack in the battery swapped it out and now this 05 is alive and running great.


r/prius • • 14h ago

Buying/Selling Advice 2015 Prius Three?

2 Upvotes

I've found a 2015 Prius Three with 140K miles for $9.5K (WA state). I'm really just looking for a car that will get me places with relatively little stress on my part. I won't be using it for a daily commute, but have to do ~150 mile highway drives a few times per month.

I know very little about cars, but looking at the carfax report it doesn't seem to have had any major maintenance like anything to do with the hybrid battery or catalytic converter.

My budget is ~15K all in including any immediate repairs.

Does this seem like a good buy? Anything in particular I should ask a mechanic to look for when getting it inspected?


r/prius • • 1d ago

Mechanical Help Found This after changing Oil

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35 Upvotes

From a 2015 Toyota Prius Two. I saw these little pieces after I changed my oil and drained it. Does this mean a gasket is having an issue? What should I try to look at with a borescope or something?

The car has about 88,000 miles and drives great, usually getting between 50 and 55 MPG.


r/prius • • 23h ago

Mechanical Help Prius routine check

6 Upvotes

I do solo trips in my 2009 prius and recently I've been feeling anxious in the middle of my drive. Like my prius is going to stop working in the middle of the road.

There is nothing wrong with my prius and i have 88k on my odo.

I think the solution for me is to do a routine check up on my prius before I leave on a trip. What are some things I can check to help ease my mind?


r/prius • • 1d ago

Question why would 12v die if left on battery minder?

4 Upvotes

I was away for six months and left my 2008 prius 12v hooked up to a battery minder. I've returned home and car started first time I tried, so I thought all was well. Today I tried again because I restored my liability insurance and planned to start driving the car again tomorrow, but prius would not start. I'm assuming this means battery is dead?

Battery was an Interstate bought at Costco. It was 1 1/2 years old at the time I left, so would be about two years old now. Does battery dying on minder indicate a fault with the battery minder, or a fault with the battery itself? Is there a particular battery minder it is recommended to buy or should any work? I travel frequently so I would like to prevent this from happening on future trips.

Update: I just learned you are not supposed to start your car while the battery minder is still connected. I didn't know this. The battery minder is still connected to my car and I wasn't able to open the trunk to disconnect it so started it with the minder connected not knowing this was not advised. Very concerned now that I may have damaged something as a result of this.


r/prius • • 1d ago

Discussion These Oldie Prius' Are Still Good To Own

44 Upvotes

I have a 2010 Prius (purchased new end of 2010). Really low miles. I have to get a bunch of items replaced (normal things):

 

  • new spark plugs
  • replacement of front pads & rotors
  • replacement of front suspension (the whole thing, all the rods, the boots etc. I'm having replaced at one time).

 

First time any of these items are being replaced on my 2010. All the other maintenance items are done routinely (oil changes every 5K mi, filters changed out, new tires, rotations/balancing, fluids, etc).

 

Found a highly respected local shop that has gotten scores of excellent reviews.

I was talking to 1 of the guys who works there. He advised me to order the parts myself online (saving $$$) and he'll install those parts. He wrote down exactly what I needed, including the brand(s).

 

He reiterated to me that having a Prius without all the fancy bells/whistles is a very good thing because they are much simpler to maintain and repair as well as less costly.

 

I've been getting new car-itis, wanting to purchase a new (SUV) next year and he strongly encouraged me to keep my old Prius even if I do get a new car.

 

Just sharing the Prius love for these oldies.

Yes, at some point in the future the hybrid battery will need to be replaced...no mystery there. And I know the 3rd gen is known to have EGR/headgasket issues, as well, emerging 70K - 100K+ miles. For now, though, all appears to be fine.


r/prius • • 23h ago

Mechanical Help Power Liftgate Intermittently Not Working?

1 Upvotes

2025 XSE. Has anyone else experienced this? It’ll make an unlatch noise and then make a long beep like its action was interrupted.

I have to manually lift it and close it to fix the issue, and I’m not sure if that’s harmful to any mechanisms.

Vehicle is still under warranty, is it worth bringing to the dealership or is it something that just occasionally happens?

Thanks for any insight!


r/prius • • 23h ago

Question What would anyone recommend for a 2021 awd xle prius for aftermarket additions?

1 Upvotes

I have a 2021 awd xle with about 25k miles on it. I wanted to do something that would be aftermarket to make it a bit nicer. I was thinking putting in those real bumpers that cars used to have, but any other suggestions would be welcome.


r/prius • • 2d ago

Pic/Video New 2027 Prius PHEV XSE

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242 Upvotes

I've joined the club and couldn't be more pleased. I was hesitating to get the XSE because I was worried about the availability and less side wall of the 195/50R19 tire size. I tried to convince myself that SE trim was a better choice but in the end power seating, auto dimming rear view mirror, and of course the 12.3" screen won the day. Big upgrade from my 2015 Honda Civic EX.


r/prius • • 1d ago

Mechanical Help 2012 240k+ miles, coolant light flashes momentarily and leaks coolant after flush

2 Upvotes

2012 Toyota Prius trim level 4, 240k+ miles. Got both coolant reservoirs flushed a month ago, and ever since then it seems to leak coolant. But its not appearing on the ground anywhere. The level is going down, and sometimes when I am driving the coolant light will come on momentarily, and then turn off. Apparently I also have a code for the water pump throwing a fault with the speeds and such not matching what the computer wants, which is a $300 fix, but I'm getting worried we are heading towards a head gasket failure.

Thoughts, comments, advice?? I can provide pictures and more info at request.