Prius Battery Adventure Time


Our story begins

While we gather our forces for our expedition to Japan, we’ve been driving around southern California in a 2005 Prius. When we bought it, the used car dealers were a little annoyed because they had had to replace the battery prior to selling it, or so they said. Our sales person reported this to us while we were driving it about. Shortly after purchase, the indicator light came on, and they discovered the battery was reporting a malfunction, requiring replacement. They could not sell a vehicle with a warning light active, so they were forced to fix the problem.

We picked out the vehicle online through a program run by our insurance company. When your car gets totaled, they know well you are in the market for a new one, so they offer you special deals through a broker. Basically, they leverage sellers to offer decent deals in exchange for a very “ready to buy” audience. Works out pretty well for everyone. It was a pretty reasonable price, and with this deal, it was a no-negotiation set price.

We showed the sales guy our set price certificate and he was perfectly amenable. He did report that his boss was not so happy due to the recent battery replacement. The cost of that hadn’t been factored into their price and it was cutting rather badly into their usual profit margin. Unsympathetic, we simply insisted we wanted the price listed, and no, we would not pay for an alarm system to help pad out their profits on the deal for them. Mind you, I was suspicious and asked for the service paperwork showing the battery replacement. Sure enough, they supplied it to me. A handy thing since we planned to sell the car in less than a year and it could help assuage doubts about the battery.

The Plot Thickens

The Prius really was in lovely condition. Its one prior owner took meticulous care, filling out all the service cards over the years, always taking it to the Toyota dealer, and generally keeping it in pretty amazing shape. It’s easily the nicest used car I’ve had. But, just this last week, warning lights flashed on my dashboard, two months after its purchase. Our original owners manual, meticulously preserved by its original owners, informed us that there was a problem of some kind with the brakes, though they seemed to be working fine. We dutifully made an appointment to have it checked out.

The Toyota dealer ran their diagnostics and determined that it was not the brakes, but the battery that was to blame. My suspicions were aroused. I’d even imagined that some unscrupulous mechanic would try to sell me on a new battery when in fact I already had a new one. The $2,500 replacement cost quoted only added fuel to my determination there must be some mistake. I let them know what I’d been told and asked them to make absolutely sure. They re-confirmed their determination. I asked about the brake indicators, they replied that when the battery gets wonky, it affects the readings on multiple systems in the vehicle and my brakes were just fine. Only the battery was in play.

When I related the story from the used car dealer, the Toyota folks said, well, perhaps that was just the auxiliary battery. They explained that a Prius has two batteries, one like a normal car for starting the engine and powering the dash, another that actually ran the car as a true hybrid. So I inquired as to the price of the auxiliary battery, a mere $200 at most. That didn’t match the $790 bill on the invoice the original dealer gave me, much closer to the $2500 for a new one at the official dealership. I decided to hold off on dropping 2.5K on the spot, do some research and some thinking.

Sleuthing Time

My main interest at this point was to figure out the cheapest way to keep my car from failing, while still being able to sell it later in the year. I started googling about Prius batteries. I soon found lots of places offering services to deal with the problem at lower price points. Most of them were pretty vague about what exactly they were offering, but one local repair center, who specialized in hybrid repairs had a wealth of information on their site. Mostly, they were trying to sell their somewhat expensive service by explaining why others were inferior. In the process, they helped clear up the picture for me.

Many places offered to fix your battery problems for a price in the $700 range. “Don’t pay outrageous sums to your dealer, we can fix your problem for a fraction of the cost!” It turns out what they offer is to recondition your existing battery. The process involves draining it, re-charging it, and in some cases disassembling it and cleaning the leads and parts. It dawned on me that this was most likely what the used car dealer had done rather than replacing it as they said. They had found the cheapest option to make the lights go out, and they took it. It still cost them 10% of the car’s price, no small repair, but it was the easy way out.

In my research, I came to learn that it’s also not an effect when used on very old batteries. The process works pretty well if the battery was simply ridden hard and put away wet too many times, but it doesn’t do a lot when they are simply at the end of their natural lifespans as ours certainly was. This was evidenced quite strongly by the fact that ours had only managed to go two months until it reported failures from when the dealer had it reconditioned. This also meant this was a crap shoot at best for me. And if I sold it, I’d be passing off a soon to fail car to some person, not so cool.

Did the dealer cheat me? No, probably not. They may have exaggerated saying it was a new battery, but then again, that was what the sales guy said, and his understanding of what the service department did probably was pretty sketchy. The people that do this work don’t really tell you exactly what they are doing or why it doesn’t always get the job done. And the price really was on par for a Prius of that age, with an old battery so it was a reasonable deal even if they hadn’t done anything. Had I been wiser, I’d have researched the car a lot more and had an idea what a new battery cost going in and known $790 was a refurb, not a replacement.


Clearly, the cheap refurbish option was not going to work for us. Nor did I really want to pony up $2,500 for a battery that would last 10 years when I’m selling the car in less than 6 months. The not especially happy medium was to get a refurbished battery as a replacement. Instead of really old ones, these are mid-life batteries that have been tuned up after a few of their cells went bad while they were under warranty. Their owners replace them, and they get re-worked for the secondary market. They cost around half of a new one and run about half as long on average. What works for me, is they have a warranty that means I won’t have to pay for it again, and I can pass it off to whoever buys the car so they know they can drive it for a couple years without having to sweat an old battery. Still a hit to my pocketbook, but such is life.

Since there weren’t many articles that really laid out how it all works, and this is probably a common problem, I whipped up a blog article on Trail and Hitch that explains the options. One thing I have learned aobut hardship; it usually makes for a good blog article.



Comments are closed.