First timer: Replacing/refurbishing traction battery

Ask Toyota for a dispensation due to the closeness of the expiration to the failure. They have been known to support some owners in equivalent situations.

Another option (about $2000) is to get a rebuilt battery - see Remanufactured Hybrid Vehicle Battery Packs

You can either read the battery details from the battery ECU using a good OBD2 instrument or, if you read up on protecting yourself from the high voltages in this battery, remove the HV battery, remove the battery top shell and then carefully read the module voltages with any digital voltmeter.

To correctly refurbish the battery you will need

• a small number of low mileage battery modules - usually only one or two have a failed cell (module voltage 1.2 volts lower than the others) unless the HV battery has been subject to overheating (check the battery cooling fan status, working? clogged with lint?)
• A number of hobbyist rechargers/rebalancers
  • I use the Supermate DC6 with an external 12v 5A supply (about $35 for the pair on the web). There are better units at about $85 each, but these are adequate.
  • It takes about 36 hours to do a 3 cycle rebalancing and there are 28 modules so multiple units speeds things up

Just wear insulating gloves until you have disconnected the bus bars on one side of the battery, there are then no dangerous voltages to deal with until you start hooking the bus bars back up.

Let each module rest after charging. They will drop quickly to about 8 volts each, but then only bad modules will exhibit noticeable self discharge rates. Also make sure to discharge all of your modules to the same voltage (but more than 7.5 volts) before hooking the bus bars back up so that your work won't have to be redone soon.

The dealer is probably giving you good information, but a full report on battery status (module pair voltages/resistances) is more definitive.

Where are you located, driving in hot weather does reduce HV battery life.

JeffD

 

Be careful! The battery pack can deliver a lot of current at 200V DC, which can kill you like a hand grenade. The individual modules are not that hazardous, but it would still be prudent to use self protection that is capable of handling at least double or triple the worst possible scenario.

 

jeff, if you did this for a living, what would you charge someone? just curious why this service isn't available, even at the dealer.

 

Some people actually do it for a living. They sell refurbished battery packs for about $1600 plus about $400 for installation.

My experience in dealing with these batteries was in rebalancing the 27 modules from my failed 2004 HV battery at 195k miles so that I could sell them as tested modules ready for use by others. It took some time to gain the knowledge and experience to do this correctly but thanks to my background in Electrical Engineering ( I am an EE Professor) and help from some others on this and other discussion groups, I was able to help 6 other people successfully use my modules to repair their Prii (2 Gen1 and 3 Gen2). I also cleared $650 after expenses selling the 27 modules so my new ReInVolt battery only actually cost me about $1300 (and supplied several months of fun as a hobby).

When my ReInVolt shows weakness (not that I expect that in the near future, they do a nice job), I will buy a recent salvaged battery, refurb it myself and swap it into my 2004 Prius.

If I were to set up a business to do this, I would have to spend about $1500 for good equipment (14 sets of high end rebalancers/chargers to allow completion of a rebuild in about 3 days) another $1500 for an inventory of good modules, and set up a working space to pull batteries and reinstall them (about 2 hours work in each direction).

Now to estimate a bottom line:

• labor ~10 hours over 4 days ~$500 for friends
• a set of modules (only two for a battery in reasonable shape) ~$100
• plus amortizing capital cost ~$300

So a reasonable drive-in out the door price of $1000 (extra if many of the old modules are not salvageable) with a reasonable guarantee of satisfaction in less than a week. As a business you would also have to add site and insurance costs so the ReInVolt price is reasonable.

I did offer to set up my local Toyota dealer with the skills and tools to do this themselves, but they did not take me up on the offer.

I am not planning on setting up this business at the age of 69 (this month), but if I were I would hire some young technically oriented people to do it if there was enough business to justify it. This actually sound like a franchising opportunity, are you listening ReInVolt.

JeffD

 

You have the option to drive your Prius up to SF. There are two great independent facilities there: Lucious Garage, and Arts Automotive, But they probably won't let you watch the whole process.

JeffD

 

He is probably not doing the full job. You really need to rebalance all of the modules to expect a long-lived repair.

JeffD

 

thank you, that's amazing. 90% labor and capital, which established shops already have. seems like a good shop could turn them around for 5 or 6 hundred dollars.

 

Jeff,

We replace headlights in pairs because if one fails, the other one will probably fail shortly.

When a module goes bad, is it a stochastic failure mechanism, or is it a wear out mechanism? If it's the latter, doesn't it make sense to start over with a new battery?

Is the longevity of a rebuilt battery anywhere near that of a new battery, or does it simply run until the next module wears out?

I'm asking because I'm thinking that if/when my traction battery goes out, I'm planning on buying a new one from a discount OEM parts supplier (e. g., parts.com). Not much more expensive than getting a "rebuilt" battery, but it should have 100% of life remaining in it.

 

The predominant HV battery failure mechanisms seem to be:

• Heat - tends to kill many modules so, in this case you are correct.
• One dead cell - As the modules are repetitively charged/discharged their cell charge levels slowly diverge. When one cell has a much lower charge than the others, it will get reversed upon a deep discharge and be destroyed triggering a P0A80 code. This mechanism can be prevented by periodic rebalancing of the modules. When rebalanced, tested for self discharge/capacity (detects approaching wear out), and set to the same voltage, the modules should have a useful life approaching that of new modules.
  
  We'll have to wait years before having the data to confirm my assertion using ReInVolt failure statistics. Assuming that these long life Prii stay in service long enough to have a second battery failure.

The new (2010 and on) modules are even better than the 2004-2009 cells (don't even consider reusing the weaker 2001-2003 modules) as they have a lower resistance and higher peak current ratings (130 amp vs. 100 amp) so I would look for a rebuilt or new battery using the newer modules.

Note that a "New" HV battery might have been stored for a long time and if not stored properly, will have used up some of it's useful life. A well done recent rebuild should last a long time, but we'll see.

JeffD

 

The whole game here is the underlying failure mode statistics. If modules fail randomly, then replacing one module should give you effectively a "new" battery. If there's a wear out mechanism involved, then a module replacement will be a band-aid at best.

My commute (and driving style) doesn't stress the battery much at all, so I'm guessing it will have a long life. If / when it finally does go, I bet that the stock of new batteries will be moving quickly enough that I won't have to worry about getting a battery that's been sitting on the shelf.

Of course, if I'm crazy, I could buy two of the Gen III batteries and rebuild my 2nd gen battery using the new modules.

 

Be aware you can't operate the battery without the straps installed. It will expand accordion style to destruction. Impressive but expensive. It must be held in compression when charged or discharged.