Home » Toyota Prius Owners Are Swapping Tired Old Batteries For Lithium-Ion Ones And Seeing Big Gains

Toyota Prius Owners Are Swapping Tired Old Batteries For Lithium-Ion Ones And Seeing Big Gains

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The Toyota Prius was the first hybrid to market when it went on sale in 1997 (though the Honda Insight beat it to market in the U.S.) and the main model line has spawned five generations of cleaner, more efficient vehicles. As you might imagine, that leaves thousands of older Prius models driving around with high miles on the clock and tired batteries. Salvation is at hand for the tinkerers out there, though. Some owners are now electing to pursue battery upgrades for their aging hybrids to unlock better fuel economy and slightly improved performance.

The key is that until the fifth-generation model, most examples of the Prius were built using older nickel-metal hydride (NiMH) technology. While these were historically cheaper than newer lithium-based batteries, they make a tradeoff in performance. NiMH battery packs are larger and heavier than lithium packs that store the same amount of energy, and generally can’t deliver anywhere near as much power.

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Thus, with aging, old-technology batteries, early Prius models are ripe for a battery upgrade. Project Lithium, also known as NexPower, is the main player in this space, offering a range of lithium cell upgrade kits for a wide variety of older Prius models. Beyond that, the company also offers upgrade kits for other Toyota and Lexus hybrids like the Camry Hybrid, GS450h, and the Alphard and Vellfire vans.

It all comes down to drivability and efficiency. With a weak or dead hybrid battery, a Prius can be a lot less fun to drive every day. It forces the car to rely more on its ICE combustion engine, and there’s a loss of the beneficial low-down torque from the electric motor when the battery can’t deliver. For a tired old car, a lithium battery upgrade can fix all those problems. It can even go further because, with additional battery capacity, the motor can work for longer before the saved juice in the battery runs out. That’s really helpful when going up long hills, or when trying to drive the car longer distances in EV-only mode.

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Jack, the man behind Project Lithium, openly shares information on the project on his YouTube channel.  In one video, he walks through the process of upgrading his 2006 Toyota Prius. After 150,000 miles, the original NiMH battery was dead. He ably demonstrates how to remove the stock battery and replace it with the new cells. The Prius’s battery is at the rear of the car, just behind the rear seats. It’s accessed by pulling out the back seats, along with a bunch of panels, trim and carpets out of the trunk. It’s important to know what you’re doing during the removal process to avoid any electrical safety issues, but Jack makes it look easy. He pulls out the pack, noting that the stock part weighs a hefty 80 pounds or so.

Out of the car, the construction of the battery is obvious. It’s made up of multiple separate blocks all connected together. In total, it adds up to an NiMH pack with a tiny capacity of just 1.31 kWh when new. Compare that to the hefty 100 kWh pack you’d find in a Tesla Model S Plaid.

2006 Prius Gen2 Nimh To Lithium Upgrade Installation Guide 7 45 Screenshot

 

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As Jack demonstrates, the interconnects between the cells are easily removed to break the pack into its individual modules. It’s very simple compared to modern EV packs, which are full of cooling channels to enable higher performance and power delivery. These modules are removed from the battery frame, and replaced with the new modules from Project Lithium, which are full of high performance lithium cells. The new battery modules can then be hooked up with the stock interconnects, the battery frame can be bolted back together, and the whole assembly is ready to go back in the car. As a bonus, the more energy-dense lithium cells mean the pack weighs roughly half as much as the stock unit. Once installed, the battery’s vital signs can be inspected via the Dr. Prius phone app.

It’s not a project that you should take on if you’re completely unaware of the dangers of electricity, but it’s not beyond the realms of the educated amateur mechanic. Alternatively, Project Lithium has a network of installers that it works with to provide customers an easier option. The packs from Project Lithium start as low as $2,455 for the Prius C, which only needs 10 drop-in replacement modules. A Toyota Highlander or GM Tahoe hybrid uses double the packs, and the upgrade kit costs closer to $5000 when it’s in stock. That’s not a bad price for a brand new battery pack, even despite the low capacity. After all, it took significant effort in research and development to engineer the packs as a near-drop-in replacement.

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Early development photos from Facebook indicate the replacement battery modules use rectangular “prismatic” lithium cells. This makes sense for packing efficiency, given the rectangular modules in the Toyota battery design. Credit: Dr. Prius/ Dr. Hybrid, Facebook

Performance benefits are slight, but noticeable, according to the company, and many forum anecdotes concur. This is because the Prius motor and supporting electronics were only designed to draw so much current, based on the capabilities of the NiMH battery. However, where the lithium battery upgrade comes in handy is that it can keep the motor running at full power for much longer than the stock pack. Thus, it won’t necessarily provide much more punch, but what punch is on offer from the stock drivetrain will be on tap for longer. It’s a boon in sustained high-load scenarios like going uphill.

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The killer app is in fuel economy, however. TheChip, owner of a third-generation Prius raved about the upgrade on the Prius Chat forums. “I managed to get 54 mpg on my round trip, even with some leadfoot driving. Previously, I’d have been around 38-42,” he noted. Do the maths, and that’s 26% less fuel, a healthy win you can take to the bank. He also noted the ability to get a full 3 miles of all-electric driving, something non-PHEV Prius models never really excelled at. Previously, he couldn’t even achieve a full mile. Other owners have posted smaller but still noticeable gains. On Reddit, owners with the lithium packs noted mileage gains on the order of 10%, or roughly 4-5 mpg.

Hybrid Repair Shop Series Troubleshoot Check Hybrid System Error Nexcell Prius Lithium Battery 7 2 Screenshot
The Dr. Prius app, from the same developer as Project Lithium, is used by many owners to keep an eye on their battery’s state of charge and performance.

A small additional benefit is that the extra battery power can come in handy for accessories, too. Some owners have enjoyed the ability to sit in their cars for a quarter of an hour with the AC on, with the engine dutifully remaining switched off. It appears that longevity hasn’t proven to be an issue in the wild, either, as some have had the batteries in use for several years now, racking up thousands of miles.

Gains to fuel economy are great, but it bears considering the costs. The kits from Project Lithium cost a few thousand dollars. So, for example, let’s say you live in California, where the gas is $4.80 a gallon, and you do 15,000 miles a year. At around 45 mpg, you’re using about 333 gallons of gas a year. Bump that to 50 mpg, and you’re only using 300 gallons of gas a year. So, saving 33 gallons at $4.80 a gallon nets you $158. Even if you were only getting 40 mpg before, you’re only saving $360 a year.

So, ultimately, swapping out the battery for better fuel economy maybe isn’t the smartest investment. Really, the biggest gains to be had are for a Prius with a dead battery. Not only will fuel economy improve, but the car will be much more drivable when it can properly use its electric motor again. Hence the tagline: “Fall in love with your hybrid again!” In that situation, even a reconditioned NiMH pack will be a boon, but the lithium upgrade is a nicer way to go. Oftentimes, it’s desirable when repairing a car to put in something better if technology has moved on. Think of it as akin to fitting electronic ignition to a classic muscle car that still has points.

Ultimately, it’s neat to see an aftermarket company spring up to provide better, more potent battery solutions for hybrid vehicles. Once upon a time, hybrids and EVs were these new, shiny things. Now, they’re becoming familiar to us, and a grassroots industry is springing up to support, maintain, and even improve them. As enthusiasts, that’s something worth supporting, especially when it’s keeping more of these cars on the road for longer!

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Image credits: Project Lithium/NexPower/Dr.Prius

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lastwraith
lastwraith
2 months ago

Gasoline might be on avg $4.80/g in CA now, but just this summer it was $7+, so that “back of the napkin math” starts to look a lot more attractive, even for an overpriced pack.

Ben
Ben
2 months ago

“I managed to get 54 mpg on my round trip, even with some leadfoot driving. Previously, I’d have been around 38-42,”

This is almost certainly BS. 54 MPG is entirely possible without a lithium battery (I’ve gotten as good as 60 on a tank in my gen 2 with aftermarket NiMH), but it’s also unlikely replacing the battery alone increased MPG by that much. For one thing, the car knows the capacity of the OEM battery and won’t use more than that. There are still benefits to the lithium batteries, but they’re not as substantial as the company may imply (shocking, I know!).

In all likelihood, this person caught some favorable weather conditions for the after replacement test drive and also may not have completely filled the gas tank. Gen 2 Prii had a stupid bladder-based fuel tank that fills very inconsistently. You need to average out mileage over several tanks to get an idea of your actual MPG.

That all said, I would have considered this when I replaced mine if I didn’t live in the Great White North where we get bitter cold temps in the winter. I’m highly dubious that an aftermarket battery from a fairly small company is going to handle that well, given that even Toyota would use NiMH in their AWD vehicles because it handles cold weather better. An aftermarket NiMH pack (not one of the super cheap Chinese knockoffs though) was much cheaper than either OEM or Project Lithium and so far it has worked just peachy.

JumboG
JumboG
2 months ago

That’s great, except they appear to be sold out of batteries. Even the ones that aren’t marked SOLD OUT on the site are listed as unavailable when you click on the individual kits.

Eduardo Kaftanski
Eduardo Kaftanski
2 months ago
Reply to  JumboG

You get on the waiting list… and get notified when they have in stock. A couple of times a year I get an email….

Torque
Torque
2 months ago

I would guess ita a pretty small company and buys batches of batteries at once to keep costs low. What’s the typical lead time from being added to the wait list to actually getting your replacement batteries? 3-6 months?

Younork
Younork
2 months ago

anyone know what the first year a prius offered apple car play?

Michael Han
Michael Han
2 months ago
Reply to  Younork

Unfortunately I’m pretty sure it’s like 18-19. My 17 doesn’t have carplay or android auto

GreatFallsGreen
GreatFallsGreen
2 months ago
Reply to  Younork

2020 was when Toyota rolled out CarPlay and Android Auto on the Prius.

Younork
Younork
2 months ago

Thank you.

VanGuy
VanGuy
2 months ago
Reply to  Younork

Just throwing this out there–I dropped ~$1000 into my 2012 Prius v on Crutchfield to add a 9″ Android Auto/Apple Carplay-compatible Pioneer head unit.

Installation wasn’t a cakewalk (especially to any non-car people) but it was definitely the easiest of any head unit upgrade I’d ever done myself.

The only thing I really “lost” in the upgrade was a volume knob, but that’s more a psychological adjustment than anything else.

Just thought I’d mention that–if a cheap older one comes up for sale, that possibility could be on your radar.

Couldn’t tell you if it’s doable/easy with early gen 4, though.

Younork
Younork
2 months ago
Reply to  VanGuy

Thanks for the suggestion

Jack Smith
Jack Smith
2 months ago

This is an excellent development. I think there’s still room for more development. For one thing I believe they could retrofit a plug-in charging system on the earlier models.

Also I am picturing removing the 80 lb nickel metal hydride pack and replacing it with about a 100 lb lithium ion pack.

Also cooling fans and maybe even a simple closed loop liquid cooling system. Maybe something made like the closed loop liquid cooling systems for gaming PCs.

These cars are so old that cutting a couple of holes to retrofit these things into the body shouldn’t be a big deal.

I could picture a 100 lb lithium ion pack getting one of these cars up to 60+ mph gallon. If the car can handle an 80 lb battery pack from the factory then it will handle an extra 20 lb. That’s about an extra 9 kilos for those people from Europe.

Torque
Torque
2 months ago
Reply to  Jack Smith

Toyota offered a plug-in model in the US at least starting with the 3rd gen. (2010-2015). I have one (2012). It is supposed to* provide 13 miles of all electric range, as long as you go easy on the acceleration And don’t go above 64 mph, both conditions will automatically (and pretty seamlessly) kick on the gas engine.

Around town (mixed highway / interstate / surface streets) avg. mpg in warm enough weather (roughly 8 months out of the year) is about 65-68 mpg US

Around town winter mpg is about 54-56 mpg US

Road trip… warm or cold weather usually doesn’t seem to matter much mpg is usually about 44-48 mpg depending on avg. mph. I can maintain 78 mph at 45 mpg US

The gas engine will also automatically engage even if you are ‘fully charged’ when it is cold out (below 32 F) and even if you dont have the cabin heat on. If you drive normally after a while it will turn the gas engine back off.

Once the “13*” miles all electric range has been depleted it is a regular gas-electric hybrid.

*due to age and milage (I’m at 222k miles), my ‘full’ all electric range is down to an indicated 9.8 miles, which now that it is getting colder here (now averaging around 32 F and still dropping), a ‘full’ ev range is down to 8.8 miles.

Jho'nuquas
Jho'nuquas
2 months ago

This puts old Prius’ on my radar for a next car now! Always thought they were fun and quirky, but was worried about battery life. Seems like I don’t have to worry anymore!

Dinklesmith
Dinklesmith
2 months ago
Reply to  Jho'nuquas

I have an ’08 with 180k miles. It’s a great car, you won’t regret getting one

Jack Smith
Jack Smith
2 months ago
Reply to  Dinklesmith

Would you consider getting this lithium ion pack for it?

Jack Smith
Jack Smith
2 months ago
Reply to  Jho'nuquas

I bet you could get an extra good deal on a Prius if you found one with a completely dead battery pack.

That would have to drive down the price a lot if the battery isn’t working at all.

If you got a smoking deal on the car and then did a DIY install on the lithium ion pack this could work out pretty well with the overall price.

Dinklesmith
Dinklesmith
2 months ago
Reply to  Jack Smith

A lot of backyard mechanics do exactly that. It’s a nice little side gig.

I’d probably get a refurbished traditional battery since I use the prius as a company vehicle so I don’t need performance. If it were a personal vehicle I’d consider it though

Torque
Torque
2 months ago
Reply to  Dinklesmith

No one is writing home about blistering performance from this li-ion pack Prii* are modest accelerators at best.
As the OP pointed out if you find a prius with the battery pack already bad or close to it, the price to replace with an original pack vs. a li-ion pack are pretty similar in cost, so might as well upgrade

*my guess at the plural of Prius

VanGuy
VanGuy
2 months ago
Reply to  Torque

A complete aside: Toyota did a (publicity stunt) poll to determine the plural of Prius. “Prii” won, but only with 25%-ish of the vote.

Dinklesmith
Dinklesmith
2 months ago
Reply to  Torque

That’s new vs new price. A refurbished unit is still cheaper

Torque
Torque
2 months ago
Reply to  Dinklesmith

True. I think referbs last I was looking we’re around $2000 and a new lfp pack for my plug in was around $3200 and a new pack from Toyota was around $5000.
So yes new lfp IS a bit more (or a lot more by a % basis) than a certified referb pack. Personally when it is time for mine, if I intend to keep the prius around I will likely go with the upgraded lfp pack.

Mrbrown89
Mrbrown89
2 months ago

People just started to look at this option for the Insight Gen 1. They are showing increased performance and better MPG (+80MPG). An old fashioned pack costs 2K but this option costs around 3K.

Insight G3 packs are compatible with the G1, also fomoco packs. The car now acts like a PHEV if the battery is fully charged, they are also installing an external charger. One day I will do this on mine but I just replaced the battery 2 years ago.

Deane Rimerman
Deane Rimerman
2 months ago
Reply to  Mrbrown89

Totally agree! I’ve been working on a project to do just that… The company has been supportive of the research as well. But I got distracted because Gen1 Honda Insight has people coding firmware for custom built BMS at linsight dot org with near 200 of these kits being sold. So I bought one for my friend’s car and am trying that easier project first.

Later on I’ll add more than one of these project lithium packs to an Insight because I’m an installer for them and have easy access to them. But that won’t be till next Summer after the DIY BMS hardware and firmware is updated to allow it because LiFePo4 is safer if you’re aiming to have way too many batteries packed inside an ultralight car.

Colin Buckhurst
Colin Buckhurst
2 months ago
Reply to  Mrbrown89

Thanks for posting this. I was reading the article wondering about G1 Insights. I kinda dig their slightly silly looks, and might keep an eye out for one with a dead battery if getting a better replacement isn’t impossible.

Reauxtide
Reauxtide
2 months ago

We’ve been running these batteries in our 2009 Gen2 Prius for the last 18 months. It was an easy choice, as the HV battery died.

We’ve had zero issues with the Project Lithium pack

Keith Hunt
Keith Hunt
2 months ago
Reply to  Reauxtide

Great to keep an existing car on the road! Curious if you did the swap as DIY or went professional install route, thoughts on the process/difficulty if you went DIY?

Reauxtide
Reauxtide
2 months ago
Reply to  Keith Hunt

Missed this reply 20 days ago… Sorry. I did the swap DIY. It took most of a Saturday, doing everything slowly and carefully.

I’d think anyone with basic hand tools and ability to follow instructions would easily be able to do it in a weekend.
A need to understand and respect high voltage is required, but it is not scary.

Keith Hunt
Keith Hunt
1 month ago
Reply to  Reauxtide

No worries! Great to hear on the DIY approach, I’ve heard similar that it is a fairly straightforward process. We just bought a 2020 RAV4 Hybrid and plan to keep it for the long haul, so any (well into the future hopefully) battery swapping would be a home project as well

Jack Smith
Jack Smith
2 months ago
Reply to  Reauxtide

Did you DIY the install or pay someone?

Goose
Goose
2 months ago
Reply to  Reauxtide

What do you do with the old battery?

David Burgenmeyer
David Burgenmeyer
2 months ago
Reply to  Goose

Lithium ion batteries are extremely dangerous n causes battery powered gimmick vehicles to spontaneously combust so if you think your gimmicks are so great just wait till your gimmick burns your house to a fucking crisp! Perhaps then you’ll learn that battery powered gimmicks are just one BIG HOAX! Just like the failed climate change agenda! Climate change is natural n not man made n anyone that fall for all this bs is a brainwashed WoKe Libtard clown!

Deane Rimerman
Deane Rimerman
2 months ago

But they aren’t selling Lithium Ion… They’re selling Lithium Iron Phosphate (LiFePo4) which is of a lower energy density and don’t catch on fire. If you look at the youtube channel the video came from you’ll see all kinds of torture tests these modules have been put through and none of those tests led to a fire.

SageWestyTulsa
SageWestyTulsa
2 months ago
Reply to  Deane Rimerman

People like the … ahem… gentleman you’re replying to aren’t interested in actually reading or understanding anything, as demonstrated by his grasp of basic grammar and sentence structure. Doing otherwise would diminish his capacity to spew his jingoistic bile at any and every opportunity.

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