Warranty Enhancement Notification?

Just read this one.... let me call dealer and get current on updates
Green Car Congress: Toyota recalling about 701,000 Gen 3 Prius vehicles in US over software issue in inverter assembly

 

So anyone else received theirs?

Yes, I just received mine yesterday - I had the recall work done 6 months ago.

 

of course it's cheaper to do the software reflash and replace only failing inverters than recall all of those inverters (700,000 of them?). they may not even have the improved inverters yet.

BTW, i had the recall done 10 months ago, no letter yet.

 

So the software update just limits power output more?

(I have memories of all those climbs out of Death Valley, fully loaded with temps reaching 108F rolling in my head)

 

now that i think about it more, by decreasing the peak power, they open themselves to some kind of class action litigation from disgruntled owners, even though 99% won't notice the difference (i noticed). the offering of the warranty maybe deals with the disgruntled part?

 

Yes this is the likely scenario;
Problem:
- IPM is not able to power output
Solution:
- limit power output
- offer extended warranty for part at risk.

From what I read about how semi-conductors fail, it is not necessarily an instant burn out process. If you stress them enough the ions migrate and it gradually fails to the point were in cannot longer work. Then it burns up. Sort of like the metal fatigue works.

 

Heat is the death of the semiconductor. If Tj increases (Junction temperature, or the temperature of the actual itty-bitty piece of silicon, not the overall package temperature) the life is accelerated.

Using the Arrhenius equation, it is easy to see. For example, a semiconductor running at 150C for 1000 hours (standard test) is the equivalent of about 189K hours. So for every second you spend at 150C vs. 55C, you decrease the life of your fet by about 3 minutes. That is a pretty big difference.

 

Good question. My impression from reading earlier threads was that perhaps instead limiting peak power, it limits the rate of increase in power handled by the relevant components. That is we still have the same power, but can't jump from zero to maximum quite as abruptly.

That said, I'm new to the Prius and never personally experienced its pre-update behavior.

 

Actually, I had a different take on what they were doing.

The documentation handed over to the feds (forget which agency.. NHTSA?) stated that the problem occurred during acceleration. They further stated that it was cracks under the big transistors, and said transistors would fall off. Which is why it was a safety recall: With all the parts flying about, if one was lucky, one might be able to motor to the side of the road. But another possibility would be that the car stopped dead, right then and there, not a good thing.

Stared at the letter, thought about this and that, and came up with the idea that it was differential expansion popping the transistors off the heat sink. That is: At the onset of acceleration, it takes time for the heat sink temperature to catch up with the transistor die temperature, causing mechanical stress as the silicon and heat sink expand at different rates.

My back-of-the-envelope analysis says that if one is looking at the temperature differences between the silicon and the heat sink, it should look like a double exponential with a peak; so, it starts off as zero, peaks at some delta-T (temp, that is), then comes down to a smaller fixed number, that last number being a function of the power output of the motors. The tricky bit is that the max temperature difference isn't associated with max power of the motor, but is rather the rate of change of power going to the motor.

So, you got distance, velocity, acceleration, jerk, and snap (x; dx/dt; d2x/dt2; d3x/dt3; d4x/dt4). It's d3x/dt3 and up that's the problem. Limit the snap (rate of change of acceleration), and one can limit the delta-T.

And, to a rough approximation, this appears to be what Toyota has done. People who have done before-and-after max acceleration tests show that the difference in speed/track time is in the noise from before the update to after the update, but people do mention that the car feels a little less "snappy". Which is consistent with the above explanation.

The other idea I had that Toyota might have done would be to take a measure of the die temperature and the heat sink temperature and limit the max difference between the two to some number by controlling the drive into the big transistors. That would directly limit the mechanical stress. They do have temperature sensors built into the trannies; don't know if they have a temperature sensor on the heat sink, though, which they would need for this to work.

KBeck

 

That's about the same thing I said in simpler language, given that at any particular initial speed acceleration will be proportional to power.

 

Mine arrived Friday or Saturday.

 

Thanks for the explanation.. makes total sense. So there is no change in output, it is the rate of increase limited. This btw should be good for battery too, and could explain why we saw the dynamic battery module V difference jump more on 2010 than on 2013.

BTW they probably do not have sensor on heat sinks, and they don't need them really. All they need to do is to measure transistor T and limit dT. The materials used for sink and glue are known properties, so if they model it in the lab they would know exactly what the limit is. Add another 20-50% for safety and deviation, and you have it.

 

I received my notice last week. When I purchased my Prius 4 on June 20, 2014, I was told that there were no recalls to be done on mine.
When I owned a 1999 Saab 2.3 turbo, the electronic "Direct Ignition Cassette (DIC)" quit on my wife going 75mph in the left lane on the highway. All systems went out and she was able to pull to the side in heavy traffic. She never drove the car again and traded it in 2005. Many owners carried a spare cassette in the trunk because of the frequent failures. I'm just glad she was driving on the ground and not 30,000 feet in a Saab jet in the air.

 

Received in the mail a notice of a warranty enhancement covering the IPM for 15 years.
Wonder if anyone else received or ??
When I purchased the warranty on the hybrid electrical system was only 10years or 100,000 miles (A CARB State such as Calif. is required to go 15 years/150000 miles.

 

As far as duplicate threads, questions, etcetera: I've found the search function here not very good. Get much better results justing using Google, looking for "PriusChat (plus what I'm searching for)".

 

I received my warranty enforcement notification today. Thanks for the posters above for explaining what the issue is.