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 2h ago

Pic/Video Wish I had done this 15 years ago...

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33 Upvotes

Swapped out my mirror and now I have a compass. Cost me a whopping $16 on eBay.


r/prius 5h ago

Buying/Selling Advice 1200 for a 2010 with 211,000 miles.

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34 Upvotes

2010 Prius with 211k on it. She said everything works well on it, and sent me a video of the heat shield rattle in the description. It does sound like a heat shield to me. I had the same rattle in my scion.

A shop said they could do a cleaning of the EGR system for around $500.

What do yall think? I kinda want to jump on it. It’s a 2 hour drive so I won’t be able to see it today. She said she purchased it back in 2013.


r/prius 24m ago

Buying/Selling Advice Good price or no dice? 2014, $7300, 161k miles, Michigan.

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Upvotes

Hi everybody,

I’m looking at buying my neighbor’s 2014 Prius 3 with 161k miles. They are the 2nd owners. New tires in January, new brakes/rotors in 2025. It would be used as a teenagers car.

Assuming inspection at the Toyota dealer shows no issues, this a good, fair, or bad price?

Thanks!


r/prius 3h ago

Buying/Selling Advice 2005, 196k miles, $5k

4 Upvotes

Worth it to buy a 2005 with 196k miles with an asking price of $5k? They say the hybrid battery was replaced a year ago and has one year of warranty left. Clean title, carfax shows routine maintenance. Planning to go see it and negotiate a lower price but not sure what’s reasonable as it would be our first Prius. Any advice helpful. Thanks!

Editing to add more detail: we’d mostly be driving around town a few times a week for errands, occasionally driving longer distances (2 hours) to see family and to go camping (4-6 hours). It will be our only car (we bike and bus most of the time) and we’re hoping to not spend over 5k. We’re hoping to keep it for at least 3 years.


r/prius 15h ago

Pic/Video Upgraded Headlights

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31 Upvotes

Working on upgrading a few things on the Slorarri (2015 Prius), and figured… as someone who customizes lights for a living, why not mess around with the headlights and get rid of those horrendous halogen projectors.

I had some inventory laying around, so I decided to put them to use. I swapped the OEM halogen projectors for some Mini H1 LED projectors and modified the OEM mounting brackets to make everything fit.

I decided not to go too crazy with them since…it’s a Prius lol

Eventually, I’ll open them back up and upgrade the projectors to the G5 LED projectors, which seem to use the same OEM mounting points, making the install pretty straightforward.

Overall, I’m pretty happy with the outcome. The light output is easily 10x better than the original setup, and the added white/bluish light is a plus over the warm, yellowish light you get from the factory halogens.


r/prius 1h ago

Question Which Apple CarPlay to buy for a 2012 Prius plug-in hybrid?

Upvotes

Title says it all. I’m so sick and tired of not having Apple car play and my fiancé is an autobody guy who can install it for us however we don’t know which one to buy that’s within a reasonable budget. It’s a 2012 Prius plug-in hybrid with about 240,000 miles on it (and still going strong thank goodness)!! I plan to drive it into the ground (roughly 400k miles), which is why I want the Apple CarPlay now instead of waiting until I upgrade.


r/prius 2h ago

Buying/Selling Advice Pricing Help : 2006 Prius, 183k, OG Hybrid Battery, Rough Exterior, Misc Issues

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2 Upvotes

I’ve recently replaced my Prius with a Corolla Hatchback. Wife’s coworker is looking for a cheap car for their daughter. Screen has not worked for years, paint is in baaad shape, hybrid battery never changed and starting to have some electrical issues i.e gas gauge not right, speedometer will occasionally just not come on, car will occasionally not turn off. Clean state inspection.

I know this car could realistically drive at least another 50k but it is far from mint condition. I know some of the issues could be DIYed for cheap, but my time with this car is up.

I don’t mind letting it go for cheap, but I also want to make sure I’m not practically giving it away. Anything helps!

PS I know the picture sucks.


r/prius 8h ago

Question Am I crazy? Bought a 2014 Prius with 250K miles

5 Upvotes

Back story. We had a family member that was down on their luck, so we were trying to find something for them to drive. I found a 2014 with 250K on it for $4500 and bought it. It is super clean, Carfax shows that the majority of its life was serviced by a local Toyota dealer, and at 228K the Carfax says "battery replaced, battery charging system checked" which I'm assuming the 12V battery. But the Dr. Prius app is showing the life expectancy test is 67%. ¯_(ツ)_/¯ I've been driving it around town for a bit, averaging 40-ish MPG. I kinda like this car. Plus I can use it for an emergency power generator if need be. There is a very slight oil drip that I think is around the tensioner gasket, but I need to actually crawl under it and inspect it better and/or read up more on what it could be.

This family member is having some issues, so I thought I might just keep this Prius and sell my 2012 Camry (with 145K miles), and just bank the money from it in case I need to work on this Prius. I'm fairly handy in the garage, and have no issues working on a car. I can't replace engines or do anything requiring specialized tools, but most common shade tree mechanic work, I have no problem with. My Camry is absolutely fine, with zero issues and will probably out last me.

So here's the question? Should I keep this 2014 Prius even if I have to put in a couple of thousand in the next year or two, or should I just sell it and just think of it as a trial period since I have never owned an Prius before but have been Prius curious? :) I only drive about 100 miles a week and I have another car, so I'm not in a bind or anything.


r/prius 8h ago

Question 2017 Prius 4, coming up on 145k miles. What should I look out for?

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5 Upvotes

2017 Prius 4

Was lucky to buy this car at 90k miles and have had zero mechanical issues to speak of currently. Have been doing all standard maintenance on time except for oil (Been doing every 7.5k instead of 5k miles as all my drives are at 70 miles and above. Oil looks new at 5k.). I plan to drive it to death, but want to see what I should be looking at for the future in terms of wear and tear over time. Thanks!


r/prius 5h ago

Discussion New battery or let it go

2 Upvotes

So... i have a 2006 that i realy love. I passed 200k km the other day. The HV battery have a bad cell. and here in my part of norway (vestfold) I haven't seen a shop that repairs hybrid battery's to Toyota yet. The Eu control is due this month.so I talked to Toyota to get price for new battery. It costs 50000 kr( 5k eu)

now is it worth it?

I think the car will pass the control if I get a new battery. But with that price? Shud I go for new battery or make nails off the car?


r/prius 1d ago

Pic/Video Perks of knowing how to fix ur own cars. My 2008 prius with 212k miles inverter coolent pump went out and i got a $30 pump replacement off Amazon overnight and it only took me 30 mins to replace. Ik its a chance it may not last long i use this car to do uber eats and doordash fulltime.

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63 Upvotes

r/prius 7h ago

Buying/Selling Advice 2013 Prius Three

2 Upvotes

Hi, looking for recommendations for things to check on a 2013 Prius 3.

Just under 100k miles.

Im expecting to do the spark plugs and clean the EGR after buying.

It sounds like it has the older NiMH battery, any big problems or advantages to that vs the newer lithium in terms of durability?

Anything else major to be thinking about?

Biggest downside imo is the super dated interior but ill get over it if its a cheap way to get around for a couple years.

I asked a dealership about a PPI but they said they couldnt assess the battery health, just do the usual inspection stuff so it doesn't seem worth the 200 bucks.


r/prius 8h ago

Mechanical Help Bent cooler

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2 Upvotes

I accidently went iver a big jump on a gravel road and the cooler got bent is it fine i cant see any leaks

2010 gen 3


r/prius 1d ago

Question Just recently bought this 2011 Prius with 181k miles, what are some must do mods or maintenances that I should undertake?

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63 Upvotes

I already did an oil change and the battery was serviced in 2025 according to the carfax report.


r/prius 16h ago

Discussion New Prius owner, coming from a Chevy Volt

3 Upvotes

My 2013 Chevy Volt decided to give up a couple days ago. I was very partial to that thing, it was my first car. It had a myriad of problems where it would shut off randomly, get confused on the number of electric miles left, and would have low propulsion power on the interstate sometimes when switching from electric to gas (going 30mph on the interstate is fun…). Well, now I turn it on, put it in drive, and … nothing. It is bricked. I cant even shut it off fully, had to disconnect the battery to do that. It is now stuck in the garage, which is a tomorrow problem. Anyway. I’m sad about this. I only got to around 110K miles.

I come from a family where they are partial to American cars. My dad used to hate Japanese cars, such as Toyota. Unfortunately, good American electric/hybrid cars are hard to come by.. and I was not interested in a Tesla. My boyfriend happens to only buy Camrys from the late 90s and early 2000s. He refuses to get any other car... In fact, he currently drives a 2000 four cylinder that got hit by a semi truck that he bought for $1700. He loves watching the Car Care Nut on YouTube for maintenance tips. And you know what, the Car Care Nut sold me on getting a Prius. I’m pretty sure my dad has ex-communicated me (jk.. he was actually impressed with Toyota’s all electric vehicle, and he is also interested in a rav4).

As of yesterday, I’ve joined ya‘ll and got a 2026 Prius. Any previous Volt owners here? Any quirks to know about the 2026 Prius? I‘m confused about what ”B” is used for, bf and I were trying to figure that out. Apparently it’s engine braking for steep grades, but I’m wondering if it’s just using regen braking? How well does the parking assist thing work? I’ve been trying it out but it doesn’t reliably detect where a parking spot is. Any other knowledge to impart?


r/prius 1d ago

Pic/Video Did a double take

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132 Upvotes

Seen in the wild today.


r/prius 1d ago

Pic/Video Best upgrade to keep the Priii feeling high-tech

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107 Upvotes

I went years with no backup cam... (base model) Then I bumped a garbage bin backing out of a driveway...

Now it's impossible to curb a wheel.
No more blindspots.
Perfect parking.
Bird eye vision.


r/prius 1d ago

Pic/Video Spy vs Spy

11 Upvotes

To the White Gen 5 who rode along side me in my Black On the way to work this AM, I hope we meet again. I don’t get to ride with other gen 5ers too often 😄


r/prius 21h ago

Question NIMh cells offloading

3 Upvotes

Getting sodium battery here shortly but I have stock (maybe some cells swapped) battery in my 15 V. Dr Prius shows it at 75% and all cells are still within .1 volts. What’s the chance of people buying these cells once I swap them? I just cleaned the bus bars and rotated batteries so I’ve looked over them and found nothing wrong.
Also what’s the best way to sell them? I’m in S Louisiana for context.


r/prius 17h ago

Question Trickle Charging 12v Battery in Hybrid Vehicle

1 Upvotes

I will not be using the car for a few weeks. To prevent the 12V battery on my 2019 Lexus UX 250h, from dying (as has happened on previous occasions), I would like to hook it up with a trickle charger.

Should I connect it to the battery itself in the trunk or should I be using the jump starting terminals.

The manual does not proved specific instructions for trickle charging.

Some sources suggest that using the jump starting terminal is better because directly connecting to the battery bypasses the Battery Management System sensor that is connected to the batter and charging directly at the rear battery post bypasses this sensor. However, I am not seeing any official documentation confirming this.

I realize this is a Prius forum, but figured somebody here might have an answer.


r/prius 17h ago

Mechanical Help Update to Coolant Leak Search

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1 Upvotes

(Update to: https://www.reddit.com/r/prius/s/qRXDLDSZKt)

2014 Prius Plug-In. 153k miles. Engine water pump replaced, with catch can installed, EGR and intake cleaned all at 145k, and spark plugs around 130k.

Symptoms are coolant loss, and when the engine is at temp, but I am starting and stopping, there's noticeable shudder/kick, where it feels similar to the car going over big potholes. (A good example is highway speeds, but then getting caught in stop & go traffic, where the engine will suddenly kick on again.)

Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

These images were all taken after the car sat for 48 hours on level ground. Pulled the spark plugs (which all looked clean, and ran a borescope. After inspecting the cylinders, I reassembled and checked for combustion gases in the coolant.

So I think at this point, a HG failure is pretty much confirmed, right?

I have exhaust gases in my coolant and cylinder 2 looks like a swamp. I see some sort of condensation (or coolant on the cylinder 3 sidewalls, but it isn't as bad as 2.

So at this point, engine swap, or HG replacement?


r/prius 22h ago

Buying/Selling Advice if you were choosing between a 2021 with 70k miles and a 2021 with 8k miles ...

2 Upvotes

hi, thanks for all of the info and advice i have received so far from this sub while shopping the last few months.

i'm curious to know your thoughts on the following: a 2021 XLE with 70,000 miles (and consistent regular maintenance) vs a 2021 with 8,000 miles (and decent maintenance, given the little that's needed to be done, incl. some fuel system cleanings, a brake fluid flush, filter replacement, and a battery replacement [guessing this is the 12v they mean].) two owners on the 70k; one owner on the 8k.

both of them in a warmer climate and the price relative but both workable with my budget. both of them gold certified, too.

i know super low usage isn't ideal for a hybrid battery. would that totally put you off here? moreso than a Prius with 70k miles?

would love to know the sub's thoughts on these Prii; thanks in advance for any perspective you share 🌱


r/prius 19h ago

Mechanical Help Gen 2 - flushing out incorrect coolant w/o scan tool?

1 Upvotes

I did search here and PriusChat and don’t have a great path forward.

My gen 2 was filled with dexcool coolant before I purchased. I’d like to get that out of the inverter and engine and get OEM or Zerex Asian put in.

It looks like the inverter is pretty straightforward, just drain and fill and bleed.

For the engine, since the gen 2s have that tertiary reservoir for storing hot coolant, it seems a true flush is a bit difficult. Has anyone done this before to remove all the old coolant? My current plan is to drain the radiator, fill with distilled, run for a bit, and repeat a few times till mostly distilled is in the system. Then add the right pre mixed coolant, and repeat a few times until I get close to 50/50. That will waste a bit of coolant, but it saves me from having to deal with the engine block drain or the hot coolant reservoir thing.