Prius Battery Rebuild: Yes or No?

Our original blog on Prius battery failure vaguely describes rebuilding HV packs as one of the services we offer.  Since it was published (over two and a half years ago) HV battery diagnosis and repair has become common place.  On average our shop sees at least one battery failure per week, and countless more are being replaced at the dealer and other Bay Area independents.

About a year ago I published another blog to streamline the conclusions from the original.  The emphasis was rebuilding, written at a time when our in-house rebuilds were at their peak: in frequency, ease, and success.

Today’s blog focuses on increasing complications rebuilding HV batteries based on our continuing experience.  It is written to help decide which route to take (new or rebuilt) mostly for those web-savvy folks teasing out alternatives across the country.  It is detailed for those seeking the most information.

To summarize earlier blogs, the basis for rebuilding is three-fold:

1. Better technology

Second generation Prius (Gen 2) modules are improved over Gen 1, but still fit in a Gen 1 battery chassis

2. Available parts

Gen 2 Prius are more common, making used battery packs easy to obtain

3. Less expensive

Despite additional labor to rebuild, the total job amounts to $600+ savings over brand new
Given these factors, why not rebuild?  It’s no surprise our customers have overwhelmingly chosen rebuilt packs.  It’s ideal for us: we can save people money while making more money ourselves (in labor, rather than just paying Toyota for the new part). 

As time goes on, however, these factors are no longer cut and dry.  We have also discovered pitfalls in the process itself.  What’s new:

1. Competition for parts

2. Growing awareness of Gen 2 battery issues, in their own right

3. Growing awareness of battery module damage due to over-handling

I will extrapolate on each of these below.


While I don’t honestly perceive LG as “ahead of the curve” on these repairs, the wave of failures has definitely crested since we opened in 2007.  This trend has increased demand for parts AND other businesses willing to meet that demand.  While we may have had some influence in consumers’ willingness to rebuild (acknowledging the process as doable, and discussing it online), many other sites (PriusChat et al.) discuss its feasibility. 

ReInvolt was the first business (to my knowledge) to sell rebuilt packs to the public (across the US, not just customers in a shop).  We discovered them in September of 2009, and I had the pleasure of meeting Dave Taylor at ASE headquarters in Virginia shortly thereafter.  Their business has put a high demand on the Gen 2 packs on the east coast region, and ReInvolt has become the leading representative for Prius battery rebuilding.

In the middle of last year, we noticed a shortage of Gen 2 packs on the west coast.  My rep at LKQ narrowed the purchases to “Battery Boy” in Healdsburg, CA, just north of San Francisco.  The shortage of packs made it increasingly difficult for us to “match” modules into a pack. (Gen 1 packs are 38 modules, while Gen 2s are 28; thus to make a Gen 1 pack from Gen 2s you need to blend or match modules from multiple Gen 2 packs.)  We were matching based on rest voltage and then bench testing swings in voltage under load, once a pack was assembled.

Preparing to go to battle over parts supply, I combed the Internet for information about Battery Boy’s operation, only to discover evidence that his process for “matching” modules was a lot more intelligent than ours.  I invited Ted for a visit and, recognizing LG as a potential partner, he shared his methods for battery testing.  Rather than argue access to salvage parts (or steal his testing procedure), the obvious choice was to buy pre-matched modules directly from him.  Though this increases the cost of the parts, it is still much less than buying a pack from the dealer and saves us the headache of trying to match modules in house (an increasingly labor intensive process).

In short, at this point we are buying packs from our competitor, with the hope that local folks will opt for the convenience of an SF location (Healdsburg is still 90 minutes north, without traffic) and the professionalism of a bona fide shop.  In keeping with our ethics, I openly admit our product (the battery modules themselves) are identical to the ones sold directly from Battery Boy.


Besides competition for Gen 2 packs, the packs themselves are only getting older.  When we first started rebuilding, Toyota was still making new Gen 2 Prius, making the supply of “fresh” packs seemingly endless.  No longer.  Gen 3 Prius have similar modules (for now; the transition to Lithium is imminent) but salvage units sell at a premium (the car is still so new).  The true supply of updated modules (Gen 2 or 3) is highly competitive (see above) and many packs (from 2004-2005 model years) have an excess of 100k or 150k miles.

In 2007/2008, the Gen 2 Prius was seemingly invincible, especially compared to the Gen 1 (Toyota’s freshman effort).  Now we’re starting to see failures of Gen 2 packs (the first was a 2005 with just over 150k miles) and a few customers have reported getting replacements at the dealer under the 10yr/150k mile warranty.  Most of our experience with Gen 2 pack failure is from taxi cabs.  Some of these die prematurely due to overheating (reference the blog on clogged fans); death by natural causes usually occurs between 200-250k miles.  But cabs are all mileage and no age.  It is unclear how long the packs will last by age (rather than use), given that the second generation of Prius is only now reaching the age (8+ years) where we started to see predictable Gen 1 failures.

At this point I have much less confidence saying Gen 2 batteries are significantly improved over Gen 1, at least in terms of battery life.  This pertains to Gen 1 owners who are hoping Gen 2 modules will last longer as rebuilds, as well as Gen 2 owners outside of warranty.


Even when buying vetted modules from Battery Boy, we encounter weak cells that diverge right away (during testing in the rebuild process or a few weeks after) and cracked modules leaking electrolyte, setting P3009.  Though the failure rate is not overwhelming, it is climbing.  The most recent jobs have required redos 50% of the time. 

LG will not pursue services with a 50% success rate.  Our east bay counterparts Art’s Automotive have never entertained rebuild packs, and I’m starting to appreciate their stance.  We’ve always presented the procedure with caveats compared to replacing with brand new, but repeated battery failures are unpalatable. 

Weak cells may be mis-categorized or simply tested improperly by Battery Boy (who processes hundreds of modules).  A rash of cracks (leaking electrolyte) was originally attributed to dropping modules and still using them (when they should have been discarded).  We are still learning best practices.

But most recently we had an electrolyte leak from a pack that had been in use for over nine months. To be clear, this is not a leak from deposits (see another blog on P3009) but a literal crack at the bottom of the plastic, leaking liquid to the metal case. Having served for nine months without issue, this kind of comeback is the most alarming, as we can’t honestly foresee such a problem during the assembly process.

The only explanation I have is that the modules become intrinsically weaker in the course of handling that takes place between sourcing from the donor car, shipping, testing, reassembling in the new pack, and installing.  Of course this is just a hypothesis based on a small sample of issues compared to the total.  But we are highly sensitive to problems as they present themselves, so we don’t miss warning signs.

Where does this leave us?

Luscious Garage no longer recommends rebuilt battery packs as an alternative for Gen 1 Prius owners looking to save money.  When presented with the latest information, our customers opt for new packs as a reliable repair.

We continue to support our past rebuilds with a one year warranty, the same as Toyota extends to its brand new packs.  All of the complications mentioned in this blog were covered under warranty.  But the potential hassle of a rebuilt pack is an essential consideration for Prius owners.  What is the cost savings of a rebuilt pack really worth? 

Someone recently emailed us a link to a rebuilding manual, now available online, for folks looking to rebuild their battery packs themselves:

Toyota Prius Hybrid Battery REBUILD

I admit I haven’t put up the $80 to see what it says.  Hopefully it’s empowering to people.  That is certainly the hope of sharing our information about the dynamics of part sources and the challenges of producing a reliable battery.  Though $2299 for a replacement pack is expensive, you know exactly what you’re getting, which has certain value the more experience we have in the battery field.

Need help with a battery problem?  Email us for an appointment….