HV battery possibly going bad, dealer said so too?

Perhaps you could make a video of this happening.

Usually the Prius will have to log a DTC that relates to the traction battery before the dealer will agree to replace it under warranty. Your service advisor is probably going out on a limb by saying the dealership would be willing to take action on the basis of the SOC display dropping quickly.

 

If it was me, I would sure check the 12 volt battery, before swapping the HV battery.

 

So even with a new 12v, it is still doing this?

 

I have had mine do that from time to time. I'm at 90K now and the dealer tells me as long as it regenerates to "any level" I'm they won't even look at Error logs. here in NY its only 100K warranty on the HV.

I have had the car for two years now, only twice seeing a green condition. its allways blue. I have very short in-town drives, over 90% of my drives are highway and are 40 plus miles one way.

I have noted that when I have seen the HV do this it has been on a hot day and the auto temp is at max trying to cool the car. since you are in CA hot in NY is normal there. do you leave the Auto temp on when you shut the car off?

 

Desertrider: I wouldn't panic - you've got 20,000 miles of warranty left. Even then, if you have a record of this issue and it keeps recurring after the warranty expires, you should be covered. It's annoying that you aren't getting the mileage you're used to getting. Have you considered taking it to another Toyota dealer for a secon opinion?

 

Here is an example of the battery report that the Toyota Techstream scantool software produces. You might try to get a copy of it from your dealer.

This report is from a normal condition 2006 Prius with about 40,000 miles on it. Any comments about what values to look out for would be welcome.

 

Look again. NY has same emissions warranty requirements as CA. It's 150K on the HV battery.

 

This diagnostic report shows that the difference between minimum and maximum module voltage is very small (which is good) and also shows that module internal resistance is very small (which is also good).

If the OP obtained a similar report for his car, my belief is that report would show a similar result. Otherwise the OP would see the master warning red triangle light as well as the MFD hybrid vehicle or traction battery warning icon.

The problem with the diagnostic report is that it does not show capacity of the modules, which has undoubtedly diminished in the OP's car, since it has logged 130K miles. Note that the Toyota hybrid system warranty does not guarantee that the traction battery capacity will remain the same as a new car.

If I was the OP I would be inclined to "stress" the traction battery by taking a drive to a local mountain (for example Big Bear or Lake Arrowhead, or head north on I-5 to Tejon Pass.) Or find one of those roads that has a sign saying to turn off your AC to avoid engine overheating, that would be ideal.

Drive uphill as quickly as possible with the AC on full blast, to put the powertrain under heavy load.

When the car loses power, do any warning lights come on? What does the traction battery SOC gauge show: one red bar, no bars, or what?

Can you take a video that shows the car is READY, the shift selector is in D, you are depressing the accelerator pedal fully, and yet the speedometer reading is declining?

 

drive it goin uphill to you hits red so burn up faster..thats what the dealer want..

 

Maybe fill out the mpg questionnaire, there could be other factors.

But in the mean time, consider this: Very very few other cars will even get close to the "low" mileage you are getting now.

 

Was that photo taken 10 minutes after you had started the car for the first time that day? Or was it taken after the engine was already hot, you had turned the car off, then turned it back on and driven it for 10 minutes?

If the former, normal behavior would show the first bar at around 25 mpg because the engine is cold and the ignition timing is retarded upon first startup. Lots of energy is expended on warming up the catalytic converter.

Then you would expect to see subsequent bars at 45 mpg or higher depending upon driving speed, terrain, etc.

I am wondering what is the engine coolant temp when the drivetrain has warmed up. Normal temp would be around 190 degrees F. Perhaps you might ask for this to be checked when you take the car in, as engine coolant temp is accessible to the Toyota diagnostic laptop. (Or if you have an instant read IR thermometer, you can measure the temp of the thermostat housing yourself.)

If the thermostat stays open, then engine coolant temp will be below normal and the engine will operate less efficiently.

I would also ask for engine ignition timing to be checked. Perhaps the timing is running retarded which will also cause inefficient operation.

Have the iridium spark plugs been replaced yet? Have you already checked other items such as tire pressure, wheel alignment and parking brake drag?

 

Hey, did your RPM go up significantly when you saw the red bars? I had a similar experience a few weeks ago. My SOC went from 60 to 35 on the ScanGauge. I've never seen it go below 40. I have a 2005 with 168,000 miles. Also, I have the Enginer plugin kit installed. I figure that was my problem. Weird things happen in the heat. I just disconnected it because it is too hot to use it right now, and everything seems to work normal. I just went to Vegas last week, and the SOC never went lower than 40, which is normal. Further, I've noticed that the RPM will increase significantly if the SOC is below 40 when the car is on the move. Peace.