Just had to replace the Main Battery in my 2001 Prius

I haven't replaced mine. The new battery pack will last until it fails.

I'd like to hear from the Prius Techs as to whether or not one should pull over under these circumstances or keep driving to a more convenient stopping point such as a gas station with a towing service.

In my case there was no option of driving to a more convenient place. The IC engine sounded like it was running 8,000 RPM and was producing very little power. I was just able to move accross the three lanes on I75 to the shoulder before it lost all power.

Sounds pretty grim. Eventually, every battery will fail, just like every hard disk drive. I was hoping it would fall back to an ICE only condition. I suppose the main battery is running stuff necessary to ICE operation. I realize Toyota expects the battery to "last the life of the car" but practically speaking about half of all cars are going to last longer than the average of all cars.

I have read many accounts of people running out of gas and the electric motor allowing them to limp to a gas station. But evidently the ICE is not very functional as a standalone power plant.

It would have been nice if the Prius had provided a little more warning when the battery condition was nearing its end of life since the battery failure will immobilize the car.

I would appreciate your taking your case to Toyota and asking them to engineer a fall-back to the ICE for future models. I'd do it myself, but having evidence of a failed battery and having endured the consequence of it's failure to fall-back gives you more credibility.

I really doubt they would do anything for the 2001 version of the Prius, they may of already addressed the problem in the new model.

The reason that the ICE just revs up with no power being delivered when the main battery fails, is because the delivery of power to the ring gear of the Power-Split-Device (and to the wheels) is dependent on there being power delivered to MG-1 to counter the torque of the ICE. Otherwise the Sun gear just spins and no torque is delivered to drive the car.

Dick

Thanks for that explanation, I have been trying all day to figure out why the ICE behaved the way it did when the battery failed.

Will the newer Prius fail in the same manner if the main battery is lost?

Allen

out of curiousity, have you had the SSC 40G hybrid battery resealant campaign done (or whatever campaign # it is in your home country)?

My car was not subject to that recall.

I have only had the steering rack and computer recall's

Yes. The mechanism is substantially the same.

odd, as nearly nearly every NHW11 (except for some late 2003s) were subject to the battery resealing campaign, along with the early Estima hybrids (same battery pack). It's about a 4hr (half-day) procedure, thanks to the curing time. You probably were asked to clean out your trunk for it, so that they could work on the hybrid battery (access is through the trunk).

Info from the dealer's notification letter for the SSC 40G: VIN Range Year, VDS, Ranges

2001, BK12U, 0002009 - 0038684 2001, BK18U, 0002001 - 0038005 2002, BK12U, 0038687 - 0070195 2002, BK18U, 0038685 - 0070196 2003, BK12U, 0070198 - 0082299 2003, BK18U, 0069295 - 0082310 With the note to check the Dealer TIS to be sure that the vehicle in that VIN range actually is involved...

Since you say that your 2001 was part of the power steering recall, and that only affected 2001s in the VIN range 0002009 - 0007793, May 9,

2000 - July 21, 2000 production, then you probably should've also received a letter for the SSC 40G. (Unless you're talking about the steering shudders, which wasn't a recall but a warranty extension...)

The only "recall" of a NHW11 computer that I know of is LSC 30D for some early 2001s. (Mine, produced in Dec. 2000, was too new for the campaign...) That was for a new PS ECU.

You may have had the ECM replaced under a TSB (as I have), but that's not a recall - no letter is sent out to you, the replacement is only if you come in reporting certain symptoms (which includes certain error codes).

You are correct, the ECM was replaced when I complained that the car was "surging" at highway speeds. When the dealer explained that it was a known problem and Toyota would replace the ECM I just assumed it was a recall item. But I never received a recall notice for the battery and when I last had the car in for its service call, I has the service manager check to see if there were any outstanding recalls or TSB's that applied to my car. He told me nothing was outstanding.

Allen: Yes, this inherent in the design of the Power Split Device of the Hybrid Synergy Drive, and it works this way for all Prius models. It is very hard to explain in words just how this planetary gear train works, but it can be seen, with a really terrific description, at Graham Davies web site at:

on the Power Split Device page and you can study his moving diagrams and descriptions for hours. Dick

That's just great Dick. We can only hope Toyota will re-design the device so the ICE can propel the car if the main battery fails.

Toyota places a lot of faith in the main battery. They have designed software that they think will keep the battery working for the life of the car. So designing safe/driveable failure modes for the loss of main battery probably was not high on the engineers list.

However, the battery is constantly monitored and will generally show signs of impending failure long before it actually fails. I just want the car to give me a warning that something really bad is going to happen in the next hour or so, so I will no be surprised when the car dies on the expressway.

It is taking 3 days for the dealer to get a new battery in to repair my car, If I had been on a long trip hundrends of miles from home this would of been very bad. I would of liked a "HAL" like announcment on the display that there is an 90% chance of total battery failure within the next 72 hours.

hehe, I.m getting kinda old. Can we ger a human beiing version when that's accomplished? Thank You.

Yes, that would be nice. I don't know much about the Prius battery technology but I have experienced the sudden, completely unexpected failure of lead acid batteries. When a plate collapses it starts a rapid domino effect of successive failures yielding a completely shorted cell. On the other hand, I've experienced the gradual deterioration of the batteries that run my cordless drill. As they age, they hold their charge for ever shorter periods. I've got one right now that takes a full charge in the typical 30 minutes, as indicated by the charger's light, but can sustain operation for only a few seconds.

I'm betting Toyota's engineers will eventually develop a fall-back to the ICE. Certainly this isn't going to do anything for my 2005, but perhaps it will for my 2008 or 2009.

Not functional at all if the electrics fail; the electrics provide the "ECVT" transmission action. It makes sense the ICE would rev freely under those conditions. It is interesting that without the battery operating the HV system is basically inoperable, but it's not terribly surprising.

Like most of the other battery failures I've read about (mostly in the Yahoo! forum), this one is almost certainly a failed connection inside the battery pack. This is the first sudden total failure I've heard about, though.

Mike