My friend David Marcus, a writer and author like me, called to say that his 2005 second-generation Toyota Prius with 120,000 miles on the clock just sent him a dreaded signal — a big red exclamation point warning light indicating trouble in the hybrid system.


Dave’s Toyota dealer on Long Island charged a $150 diagnostic fee to tell him he needed a new nickel-metal-hydride battery pack, and that because the car was out of warranty (since it hit 100,000 miles) he would be charged $4,000 to replace it. “I don’t have $4,000 sitting around,” Dave told me. “And I need that car.”


Yikes! That’s a lot of money, and unexpected since very few 2005 Priuses from that year, with that kind of mileage, need new batteries. For a long time, Prius battery replacement was pretty rare — the company pointed out that some had reached 300,000 miles and are still going strong on their original packs (like the one at right). The first-gen Prius appeared on the American market in 2000, and more than 4 million have been sold worldwide since. So with some cars being 12 years old, the warning lights are coming on more often.


Plus I’d heard that Toyota lowered the second-gen battery pack to $2,588, so the quote seems high. Furthermore, since New York is a California emissions state, I thought Dave’s pack would be warranted to 10 years/150,000 miles (not the eight years/100,000 miles of other states). I was confused.


The Prius now comes in four variants, and all of them are selling well — in June, 19,150 were sold in the U.S. The number of Prius owners is increasing exponentially. So the battery replacement issue seemed to be worth a new look, and some clarification. There's a ton of Internet chatter about this, but not all of it is correct.


The first thing I found out is that the price of Prius batteries has changed again. The new price is $3,649 for either the Gen-1 or Gen-2 packs, but before you panic, there’s a $1,350 “core credit” for your old battery, as long as it can be recycled (ie, wasn’t destroyed in an accident). So it’s $2,299 for everybody with a trade-in, plus installation.  


If you still don’t like the all-in price quote from your dealer, you can negotiate. John O’Dell of recounts the story of a first-gen Prius owner, Heather Knowles, who was first quoted a whopping $5,785.76 for a battery replacement that also included a new management computer and new wiring. Sticker shock! But after some back and forth (including Edmunds contacting Toyota’s corporate office), the price went down to $2,299 plus $650 labor.


I’ve heard anecdotally about other people getting dealer prices lowered, and also of out-of-warranty claims that Toyota ultimately “made whole.” Don’t fall victim to that uniquely American disease of taking price quotes at face value.


Dave also says his dealer professed ignorance about used Prius packs, but due to accidents and other factors there are a number of them out there — just check eBay or Craigslist. I saw eBay prices from $850 to about $2,000. There are also companies like Re-Involt that offer “remanufactured” packs (with an 18-month/unlimited mileage warranty) for $1,875 plus shipping and the old battery.


It turns out, by the way, that Dave doesn’t have to go to the poorhouse over his hybrid battery. Despite what the dealer told him, he’s covered and his battery will be replaced at no cost to him. “There seems to have been some confusion about that at the dealership,” Toyota’s Wade Hoyt told me.


There are other solutions, of course. I found a website claiming that since it’s usually a few cells that go bad, you can buy their instruction book, replace the bad ones, and be back like new for something like $500. It sounded like an Internet scam to me. Toyota is definitely skeptical. “I believe that our battery packs are assembled in clean rooms for a good reason,” Hoyt said. 


Speaking of that, I also found a step-by-step photo section for replacing your own battery pack. Scrolling through it, I have to conclude that the process — which the poster seems to find easy as pie — is likely beyond the casual Prius owner. It doesn’t look easy, and high-voltage electricity is not something you want to play around with. There are also videos, such as the one below, that take you through replacing the pack, in this case on a 2006 Prius:



My advice is to not attempt this replacement job yourself unless you're experienced with both working with cars and have a healthy respect for electricity. Note how, in the photo essay above, the author forgets to wear his insulating gloves at one point. So get someone experienced to do it, especially since the labor isn't the costliest part of the whole exercise — it's still that expensive battery pack.

Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.

A primer on replacing the Prius pack
Much of what you may have heard about new batteries for your aging Toyota hybrid is probably wrong, and there are some new replacement twists, including a new (