2005 Prius hybrid battery failure experience

I decided to join the forum to post my experience with the hybrid/traction battery failing in my 2005 Prius. It only has about 154k miles on it, so it hasn't been through a terribly hard life. I wasn't pleased with the prospect of having to buy a much newer, more expensive, car in order to get something with less miles (if it came to that).

In hindsight there had been some clues with surges from the engine as it probably was taking up the slack on certain terrain before any instrument cluster lights showed up. When they did I got the check engine light, the circled exlamation point, and VSC indicators. (My red exclamation light is always on due to a headlight stabilizer malfunction that hasn't been addressed.) I unhooked the aux battery a few times to clear the code, and it would come back after the second drive, then each time.

The performance got noticeably worse with the engine running almost constantly. After reviewing other posts on this forum, I watched the battery bars closely and saw wild variation within a minute, so the engine was doing most of the work and trying to charge the pack without success. The mileage dipped sharply into the upper 30's, which is funny and sad at the same time - even a wounded Prius has better mpg than most ICE cars... I also heard the fan running in the back seat, and to be honest I'm not sure if I've EVER heard it before. Maybe on a super hot day years ago, but it's very unusual.

At that point I was pretty convinced it was the hybrid/traction battery, and the friendly O'Reilly staff confirmed that's what the code meant. I started researching hybrid businesses in the Cincinnati area but decided to give Toyota (King's Toyota specifically) the first pass. I had a good conversation with the service rep about the symptoms and told him that I wanted to know as much about the battery failure, if that's what it was, as possible, because I'd been looking into reconditioning or repair options even though they don't do that.

It turns out there were two weak cells causing the problem, and he quoted about $2700 to replace the whole pack. I called another place, and they probably did more to convince me against the other options than Toyota. They said they had no luck with the reconditioning, so they don't offer it. They could install a remanufactured battery for almost the same price or a new one for even more. So in the end I kept it at Toyota. I should have gotten it back this afternoon, but for some reason it's taking longer, and I expect to have it back tomorrow morning.

I'll report back after I get it. I'm still interested in battery conditioning though as a preventative maintenance measure. My solar charge controller does the maintenance overcharge to the batteries to extend their life, so I'm familiar with the concept. Maybe I can stave off another failure on the next pack or our Highlander Hybrid's pack.

 

After a couple weeks the new pack still is doing fine, and the car is getting better mpg than it has in a long time. It seems like over the past year or two it's been difficult to get above 45-46 mpg, but now it's a little over 47 mpg. One disappointing thing is that they told me it's only covered by a 1-year warranty. There's another post around here that suggests there was a letter sent to dealerships that it should be a 3-year warranty, but the implementation seemed spotty. I'll take it up with them if there's a problem, but I don't think it's worth arguing about right now.

Does anyone have suggestions on monitoring and maintaining the traction pack along the lines of reconditioning to keep it healthy?

Thanks.