Why Prius ECU can't reduce battery temperature while Dr Prius app can?

The fan is supposed to come on somewhere right around the temperature you're talking about 117 122 something so maybe you flip the doctor prius app too quickly . And I would have trouble thinking 120° is any kind of massive temperature for a big metal battery like this but be that as it may That's only a few degrees hotter than a person well 20° or so that's not very much so I can't imagine 120° would be any kind of serious not good situation.

 

Do not assume that the temperature thresholds Toyota selected for their fan program are the same as the thresholds set in the app for text display color.

 

May have a clogged battery blower wheel.

 

the ecu does reduce battery temps by changing the blower speed as necessary

 

I think that what Leadfoot means is that Toyota engineers don't consider 120° to be too high. The ecu will turn the fan on when it's programmed to, and will set codes if things go bad.

Yes, it's generally better to have the battery cooler, but the OE design has worked quite well for hundreds of thousands of Gen2's. You can play with the fan if you want. I ignore it and use the A/C when it makes sense to.

They likely had to balance noise from the fan (& power use) vs temperatures.

Posted via the PriusChat mobile app.

 

Yes that's part of it.

I don't know what temps Toyota thinks are okay. I do know that they spent a big bag of money figuring out how much cooling air the battery should get, and a lot of high-mileage cars on the street means they did pretty well as far as I'm concerned. I'm sure they didn't want noise complaints, and they didn't want the fans to wear out in 3 years and leave the battery totally unprotected after. We know they were on the hook to maintain very long warranties on the batteries themselves, so they were motivated to make it last. A delicate balance.

The bigger point is that the car ECU is running one set of code to keep that battery cool, and the Dr. Prius app is running completely unrelated code to display and evaluate those temperatures and say whether the car is OK or not. You are the only thing coordinating these disagreeing phenomena.

Because these are two disconnected systems doing different things with the same voltage and temperature data, they will always disagree slightly and give you reasons to doubt one or the other. That doesn't mean it isn't useful as a tool, just that you need to be ready to read between the lines.

 

Dr. Prius has to be running continuously in order to control the fan or else the cars ECUs take over.

 

I was under the impression that Dr. Prius (and Torque Pro) did not have any intelligence behind the battery fan override. This might not be too much of a concern if you override to run the fan at speed 6 (full speed) but if you set the speed to (say) 4 and the ECU wants 5 or 6, it won't be able to set the fan to the speed it wants until you stop running Dr.Prius. So there is that consideration.

 

The ideal Hybrid Battery temp for a Gen 2 and Gen 3 Prius is between 77°F-104°F. When the HV Battery is outside of this temperature range... the Hybrid Control ECU begins to throttle charge in and out of the Hybrid Battery due to how temps affect internal resistance and to protect the Hybrid Battery. You can watch this happen in real time by monitoring the MAX Charge Parameter in Dr. Prius. 33.5HP is the maximum charge allowed into the vehicle... when it is outside the ideal 77-104°F temp range the MAX Charge parameter will be less than 33.5 HP.

The Hybrid Battery fan kicks on low at about 100°F and stays off until that point.

At about 127°F... the Prius effectively stops using HV Battery power to propel the vehicle... the only time after this point the HV Battery provides power output or charge to it is under heavy acceleration or if the HV Battery is low.

At 132ish°F... the Prius HV Battery fan kicks on to high. Before that point... the fan is on at a quiet speed... but the Hybrid Control ECU will be taking other measures to keep the battery cool like severely restricting charge in and out of the Battery during Acceleration and Regenerative Braking.

The Red warning you're seeing at 120°F in Dr. Prius is arbitrary and just how @jacktheripper (Dr. Prius) programmed the app. It is not overheating... but the Hybrid Battery is not in it's ideal range.

Reconditioned Hybrid Batterys heat up very easily due to being an old battery and the wear causing increased Internal Resistance.

Everything you've experienced in your post is 100% normal and nothing is wrong.

This is false... the Hybrid Control ECU will override any external input whether from an app or from techstream during conditions that require the Hybrid Battery to be protected... If the Hybrid Battery is too cold... you can't even turn the fan on. (Tested when below 50°F)

If it's too hot (above 132°F) the fan will run on high no matter what. Up until 132°F the Hybrid Battery fan runs at a slow speed.

 

You’re making an assumption that may not be true: the fan can run at multiple speeds and it’s not that audible.

 

I know it's a very old thread, but the original post has a point about the ECU not being able to control the fan properly, and I'll tell you why:
My 2006 got to 132f recently, with the fan completely off ( i know how it sounds, i cleaned it multiple tilmes, and i put my ear on the vent, it was silent!)

I opened techstream, and founf that the ECU is trying to put the fan and mode 5.
I clicked the " active test" and was able to turn the fan properly to all the speeds 1-6
But when switching out of "active test" the fan immediately turned off even tough the battery was hot over 125f, and the ECU was trying to set it to mode 4 per the " data list" table.

So... there is something about the Auto mode that does not work, but it works in manual mode, which i believe that dr prius is using.

I have to say that sometimes i do hear low speed in auto mode, but its definitely not as gigh as it should be per the techsream mode.

So could it be the PWM signal to the fan that is disturbed by the cable corosion known issue?

If so, its strange that this PWM is working fine in " active test" mode, and via Dr prius.

Any advice is welcome, im an electical engineer , i like to dig into these things, but i dont have much time, was hoping someone experienced the same thing and has a quick fix.

Thx
Amitt

 

Toyota "Technical Information System" TIS

https://techinfo.toyota.com/

 

Thanks but i cant open this link, is this for a specific known issue that can solve this ECU contol problem ?

Thank you for any tip!

 

Check the white connector at RT rear of car behind quarter trim the ductwork contains temp sensor that monitors air coming thru duct and connects to said white plug it's a known corrosion point may have to jumper out this plug bent pins corroded pins intermittent fan operation is possible beware

 

It can reduce temps when all connections are proper.

 

Somehow, the observations and speculations have to be squared with the fact that the very same PWM output pin from the ECU, and the very same external circuit downstream of that, are used both in normal operation and in Active Test.

 

Correct, i looked and pinout, the PWM and SI go through the same pins.

Indeed weird, which makes me think it may be an ECU FW issue, where the PWM in auto mode is distorted by other signals, whereas in manual mode, it looks cleaner since some other features are disabled.

The only way to find out is to put an Oscope there and see how the PWM looks in both modes.
I attached the data table, you can see the return voltage which is supposed to be the feedback to the ECU that the fan is actually spinning at right speed.

Per chatgpt, this is a problem with gen 2, because this feedback is not used to pop a fault, its just for diagnostic purposes. In any case the feedback is definitely wrong in manual vs auto mode.

Im not sure if I'll have time or energy to scope the pins, i wonder how many gen 2 batteried were blown out if it is indeed a FW issue with the PWM once the wires become compromised.

Any though will be appriciated