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These Tiny Threats Are Killing Your Toyota Prius Hybrid Battery

Ever wondered what is really killing your Toyota Prius Battery? I have the answer for you and what you can do about it.

There you were, minding your own business when out of nowhere your master warning light comes on. You take your Prius into your favorite shop of choice, and they tell you that you have a P0A80 replace hybrid battery code.

You suddenly find a pit in your stomach and want to know more. You, of course, jump on the internet and get flooded with information. None of it makes much sense until you land here.

Prius and other hybrid owners face the challenge of losing their hybrid battery. Most do not know why it occurs and what can be done about it. I want to explain in this short article what causes the cell to lose a life and the choices you should take into consideration.

Why Hybrid Batteries Fail
Any battery you have ever used works the same way. Electrons flow from one end to the other when the electrical circuit is on. With rechargeable batteries like our Nickel Metal Hydride (NiMH) and Li-Ion (Lithium Ion), electron flow is crucial.

When a battery begins to fail, it is due to the inability to flow these electrons from each side of the cell (anode to cathode and vice versa). The resistance to electron flow increases, and we lose overall battery capacity—nothing new here other than this. The culprit is these things called dendrites. The picture below shows a Lithium cell but this is also characteristic of NiMh.

Lithium dendrites in batteries

Dendrites are tiny web-like hairs that grow on the separator plates inside the batteries. As they grow, they block the flow of electrons, thus causing high resistance. Our Prius is susceptible to this over time, and there is absolutely nothing we can do about it to stop it entirely, but we can mitigate the process. See a cool story on what Samsung is doing to help make a better battery.

Options For Your Toyota Prius Battery
When a Prius battery dies, you have options. The first question you need to ask yourself is this. Do I want to keep my Prius for another 5 to 10 years? If the answer is yes, put a new battery in it. Do not go used, refurbished, or reconditioned. Go new.

2014 Toyota Prius hybrid battery in the car

The reason for going new if you plan to keep your Prius for five years or longer is this. If you already got 10 to 15 years out of your current battery, chances are you will get another 15 years out of a new one. No hassle, no mess one and done. It is the highest cost, but batteries have come down significantly in price over the years. $2500 for a new battery is a great deal if you plan on having it for another decade.

Option two. Refurbished, reconditioned, or used. This process is a temporary repair that you can get by with for up to 5 years without repeated conditioning. When a battery is "repaired" bad modules are replaced, the battery is tested and balanced and returned to a "like-new" condition.

During this process, we are halting the growth of dendrites and even restoring capacity to the battery. The battery reconditioning process does work, and it will extend the life of your battery. You need to know it is not a one and done thing, though. You will need to do it for the remainder of the days of the battery or car.

It is cheaper to do this process, and it is useful if your battery still has 50% or higher life left in it. You can test that by using the paid version of the Dr. Prius app and running their simple tests.

Dendrites are real. They form all the time when the battery is sitting for long periods. They will wipe out your hybrid battery over time. If you want to keep your current battery in optimal condition, recondition it twice a year.

If you want to swap out the battery after it dies, get a new one and be done with it. Those are the best options you have for your Prius. The only thing you need to do from here is to ask yourself how long you want to keep your Prius.

Thank you, everyone, I hope you find the information you need. I look forward to seeing you in the next story. Planning On Fixing Your Prius Hybrid Battery? Use This Tip For Best Performance.

Have questions on your Prius? Feel free to message me. I am more than willing to help. Be sure to check us out and join the movement on Facebook too at Green Car Movement for weekly giveaways and to help other people.

Watch this Toyota Prius truck with a nice little bed and click to subscribe to Torque News Youtube for daily automotive news analysis.

Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an Instructor of Automotive Technology at Columbia Basin College. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters


James (not verified)    May 1, 2020 - 3:06PM

You recommend reconditioning your battery twice a year for longest life. I see reconditioned batteries for sale, but not something that looks like a periodic maintenance reconditioning. Is there a specific maintenance procedure I should ask for?

Joe Commenter (not verified)    May 2, 2020 - 10:09PM

Can you cite any actual studies or journal articles that refer to dendrite formation in NiMH batteries? So far I've been unable to find any information online that corroborates this claim. When I look up failure modes for NiMH batteries the first one I see is loss of the electrolyte. Even if dendrites can form there, these are obviously not the primary failure mode. Also, I don't see how dendrites can form from the battery just "sitting around".

ProDigit (not verified)    August 1, 2021 - 9:35PM

In reply to by Joe Commenter (not verified)

Good question!
NiMH batteries aren't known for having dendrites, however they experience a "memory effect", which is pretty similar.
Rather than have cells short circuit, NiMh batteries just lose capacity over time (like lead acid), especially so, if the battery isn't completely drained before recharging.

Barry Malloy (not verified)    August 21, 2021 - 8:43AM

In reply to by Joe Commenter (not verified)

I learned something. So dendrites are like calcification on plates on a regular lead acid battery. And EV batteries self discharge just like lead acid batteries. Thank u!

Kevin (not verified)    May 3, 2020 - 1:56AM

Not sure I understand the point of this article. It is nice to explain dendrites, but it doesn’t seem like it will affect how people drive/maintain their Prius or prevent a failure? I have never heard of any dealership offering a “conditioning” service; doing something like this every 6 months sounds like a waste of money, as there are many HSD cars that never have a failure, at least until very high mileage.

I have been driving a Prius since 2006, over 500k KM in that time between with 2 cars. My 2006 did have the battery fail after ~273k KM (which I consider “high mileage”) and 7 years and struggled with a ~$3500 expense at the Toyota dealer in 2013 for a brand new pack, given the age and mileage (though the car was in very good shape). I ended up finding a private shop offering to rebuild for 1/3 the price and proceeded with that with no regrets, which bought me 3 more years and 120k before it failed again. I agree that if the intention is to keep the car 5+ years, a brand new pack *may* make more sense, however even in my real world anecdotal example, it would have still been more expensive if rebuilding the battery TWICE (and he gave me an even better deal - 1/2 price - as a returning customer), and it is a long gamble to pay off. End of the day, it really depends on if you have someone trustworthy (and reasonable pricing), but I would reckon the rebuild route will make more sense for most folk.

Overall, despite the battery failing, the 2006 was still a fantastic car and more than offset that expense in fuel and maintenance savings, so no regrets. :)

In 2016 I upgraded to a 2014 Plug In Prius, now with 175k KM, and going strong.