PiP Regen Behavior?

Please limit discussion to the topic of regen behavior. Post discussions of engine coolant temperature and engine-on behavior in another thread.

I have noticed on several occasions now during long descents from Mt. Hood or Creator Lake, that regenerative braking momentarily ceases charging the battery, and the engine kicks on. Watching my Torque gauges, the 3 battery temperature probes and the 2 inverter probe temps never rise above normal. The state of charge was at 50% or less, so capacity wasn't an issue.

What is the most likely cause of kicking out of regen? Have you noticed any temperature (or other) thresholds that kicked you out of regen?

I don't understand why the engine must come on when speed isn't very high and no power is required. It's one thing to cease regen, and another to fire up the engine.

FYI- Car was in EV mode with HVAC off, under 60 MPH.

EDIT:

Here is a video showing the described behavior:

 

From Mt. Hood, we're talking about 4,000 ft drop and about 10 miles of pure coasting / regen. Perhaps only the first 5 miles or so involves about a 6% grade. If I allow the car to stay near 60 mph, I can make the descent with regen kicking off just once.

Creator lake was brutal, with near full regen for miles on end. I went in and out of regen many times, going from nearly zero EV range to 8.

Outdoor temperature was probably around 50 degrees.

I'll try to remember to record what happens the next time I'm up a mountain. Might be headed to Mt. Baker for spring break, or perhaps Yosemite.

 

HVAC wasn't on, and the trigger for the engine coming on was excessive regen, not engine coolant temps. I should have also mentioned I was in EV mode the whole time except when I exceeded regen.

Good info though for those running the HVAC.

 

I'm ashamed to say I forgot one important temperature to pay attention to; MG2! I have no idea what temperature was reached as I have that gauge on a different page than my other temps.

After reading the most excellent info in this post, it appears the maximum allowable temperature for MG2 is about 150C, or 302F.

It's important to note that I have 100% blocked my lower grill, so that may contribute to increased MG temperatures.

I do have a min/max temp gauge set for MG1 and MG2, so I'll monitor these temps to see if there is an upper limit at which MG2 is forced to stop regenerating energy. I'll note the temperatures observed next time the car kicks out of regen mode. Then I'll see if there is a correlation to regen shutdown and MG temperatures. Finally, I'll see if removing the grill block allows for reduced MG temperatures, or improved sustained regen.

 

The more I think about it, the less I believe the MGs are to blame for kicking out of regen mode, but I hope to do a test soon.

That brings up my next question; what are the various maximum temperatures for the battery, inverters, and MGs? I want to set an alarm when approaching those temps so that I won't miss it. From what I've read, it seams 300F is the max for the MGs, but I'd like to confirm if someone knows.

 

The engine does not come on due to HVAC settings when the HVAC is turned off.

My particular inquiry is definitely linked to prolonged regen, and nothing else. Light prolonged regen takes much longer before kicking out of regen, and heavier prolonged regen shortens the amount of time the battery recharges before the engine turns on and regen is halted. After a brief period of no regen with the engine running, it will go back into EV mode and resume regeneration. I can only assume this is because a temperature fell back within operating range.

In my mind, the only 2 questions are:

1. what temperature probe is causing regen to momentarily turn off?
2. what is the upper temperature limit for that probe before regen turns off, and what temperature does it have to fall back to before regen is re-enabled?

 

Please stick to the topic of this thread (regen behavior, not engine starting). I'm not interested in guesses as to what causes the engine to come on. If someone knows what causes regen to momentarily stop, or has run some tests to narrow it down, that is useful. Providing info on maximum operating temperatures for various components is also helpful.

mmmodem- Thank you for providing your experience. I'm not sure if I'll drive on the 108 when I visit Yosemite next month since Google has me take the 120 from Stockton. Perhaps the Siskiyou pass will provide enough of a hill to give me the data I need.

My ultimate goal is to know what temperature threshold is causing regen to cease, and to set an alarm on Torque when I approach the limit. This way I can briefly use friction braking to bleed off some speed before temps exceed the regen parameters. I'll also experiment with providing more airflow to cool whatever component is getting too warm.

Can't be it. The regen will kick off even if I had turned the car on in EV mode and left it there, never having run the engine. Cat temperatures are only relevant when in HV mode.