Toyota Prius - How Long Will My Battery Last?

Toyota Prius

Toyota Prius

If you are considering buying a used hybrid vehicle, you'll want to read this post and do the research on battery life before making a purchase.  I thought I would share my experience below.

I was in the market for a used Toyota Prius a little over a year ago.  The Gen II Prius built from 2004-2009 was within my budget so I began research on what to look for in a used hybrid.  My biggest concern was the hybrid drivetrain and battery.

It is important to note that any battery, no matter what chemistry or size, is a consumable.  It will eventually wear out. I just finished replacing the 9 volt batteries in three smoke detectors in my house.  This is an annual routine for us and doesn't break the  bank at a whopping $10 per year.  However, replacing the high voltage battery pack in a hybrid vehicle is a completely different proposition.  They don't have a trap door for replacement and the batteries are thousands of dollars for a new replacement.

After much research, I found some reports of cab companies getting over 500,000 miles on a HV Prius battery pack.  I also searched forums and automotive sites and couldn't find any complaints of battery failure on the Gen II Prius.  (there were a few complaints for the Gen I Prius but they improved the battery pack in the new generation vehicle)  I found a 2004 Toyota Prius that was owned by a Toyota mechanic and had 130,000 miles on it.  I had it checked by a Toyota dealership and made the purchase.

After performing a bunch of maintenance on the car to recondition it, my wife enjoyed driving it trouble free for 6 months.

And then the unthinkable happened.

I noticed the fuel mileage dropping into the thirties for about a week and then my wife called me from the school parking lot saying that the dash was "lit like a Christmas Tree."  She limped it home and I checked  it out.  After a little research, all indicators pointed to a failed HV battery pack.  One trip to the Toyota dealership confirmed my worst fears.  The battery pack was dead.

I was quoted around $3200 to replace the pack at the dealer but decided to drive it home.  After some searching 6 months later, I started finding new posts of Gen II battery failures from a lot of sources.  I did some calculations and realized I was about 6 months out from having the first Gen II Prius hit the 8 year mark when I purchased my used Prius.

To make a long story short, it looks like mileage isn't the primary factor in hybrid battery wear.  It appears to be age and environment.  From personal experience and from research, if you live in a warm, humid climate (I live in the Southeastern United States) and park your Prius outside of the garage, you can expect to have the HV battery fail after about 8 years regardless of mileage.

After reviewing some of the posts from cab companies that were getting 500,000 miles out of an HV battery, I realized the cab companies were in Canada and they were putting over a hundred thousand miles on the cabs in a year!

If you are in the market for a used Prius, make sure you find out if the HV battery has been replaced with a new battery before you purchase.  If not, make sure you factor this into the price you pay for the car.  However, if you already have a Prius approaching 8 years old, you may want to consider buying a remanufactured battery and installing it yourself.  This is the route I chose for my Prius and below is a video of my installation.  This ended up costing around $1800 and the equivalent of a half day of labor.

NOTE: If you are going to replace the HV battery yourself, you must be experienced at working with high voltage electronics or wiring.  Improper handling of the HV system in the Prius WILL KILL YOU if you don't know what you are doing.  Make sure to watch all three parts of the video before deciding if you have the experience to do this yourself.  If not, you can still purchase a remanufactured battery and have a local hybrid repair shop perform the service.

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It should be noted that Thomas Edison built a battery more than 100 years ago which could outlast a human being. Some of the batteries his factory produced are still in use. One company even buys these old batteries, repackages them and resells them today. After Edison's death, Exide Battery, which produces lead-acid batteries, bought the Edison Battery Co. The company was profitable and Exide paid millions to buy it. But, they closed the factory down. Clearly, they simply were eliminating the competition to their "consumable" lead-acid batteries. Today, an improved Edison battery is being researched by a group at Stanford University and other groups as well. Edison's original design is still being produced --- in China. The Stanford researchers have announced that they have made a major breakthrough in the Edison battery which will make it more than competitive with existing batteries (see ). So, all batteries should not be considered as consumable.
Hi Bob, Thanks for the comments. The energy density of current nickel-iron batteries are comparable to lead-acid batteries so they are really not feasible for modern electric vehicles due to the weight to carry enough energy for average daily use. I hadn't read about the work at Stanford on graphene nanotubes but it looks promising! For our readers reference, there are two good books covering Edison's battery work. Edwin Black's <a href=";camp=1789&amp;creative=390957&amp;creativeASIN=B005SNNYVQ&amp;linkCode=as2&amp;tag=southerngreas-20" rel="nofollow">Internal Combustion</a> and <a href=";camp=1789&amp;creative=390957&amp;creativeASIN=0143121944&amp;linkCode=as2&amp;tag=southerngreas-20" rel="nofollow">The Quest for Energy</a> by Daniel Yergin. -Powell
According to the journal abstract (I'm not paying $32 for the whole thing), the ultrafast Ni–Fe battery can be charged in ~2 min and discharged within 30 s to deliver a specific energy of 120 Wh/kg and a specific power of 15 kW/kg. A lead-acid battery is 30–40 Wh/kg and its specific power is only 0.18 kW/kg, so the NiFe battery is 3-4 times higher in specific energy and over 80 times the specific power.
Yes, it sounds very promising. I have toured a lab in Atlanta where they have a prototype Lithium Air battery that could offer up to 3,000 miles on a single charge in an average-sized sedan. They are having some issues with how to recharge the cells and how to do it in a reasonable amount of time. I am optimistic that there will be some significant breakthroughs in battery chemistry and energy density to make electric vehicles more viable for a larger segment of commuters. -Powell
The Prius batteries are very robust, though as you found out they can fail. Did you look for batteries from a salvage yard? With millions of Priuses on the road, some of them were probably totaled and I've heard Prius batteries at the salvage yard are more like $500. Anyone know if you'd need one from a recent accident, or do they age if they haven't been used for a year or two and were sitting around a salvage yard?
how would you compare that to Tesla S?
Hi Sanjeev, If you are referring to battery life, the Lithium chemistry batteries in the Tesla Model S are also consumables. I'm not sure how long they are supposed to last. I would expect that in 8-10 years, we might start getting some feedback on how well the batteries are holding up. Keep in mind that a small hybrid battery in a Toyota Prius is a fraction of the expense of an extended range battery pack for a large sedan. I don't even want to know what the replacement cost would be on one of those battery packs. Also, I'm assuming from the bare drivetrain I saw at the Tesla store in Newport Beach, CA that the body would have to come off to replace the pack or service the controller and motor. Does anyone have any other thoughts on longevity of Lithium chemistry batteries and how they are effected by environment? -Powell

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