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Discussion Starter #1 (Edited)
This was a new one on me - maybe others have seen this behavior.

Here is the scenario: Driving home from my Dad's house which involves a hill climb that is borderline mountain-mode needed (I have been caught out once on it with the reduced power thing). I engage mountain mode as I was leaving my Dad's place, but I forgot to do it right away, so I engaged it with 3 bars of battery left. Started the "easier" part of the climb with Mountain Mode slowly catching up to the red line on the battery. Stopped at a drive-thru that went slow, and MM was able to reach the 50% SOC.

Headed out and up the big climb. Ended up getting stuck in very slow traffic, so did the climb at 30-40 mph, so it wasn't a challenge. Disengaged MM back to Normal as I crested the summit, then started on the downward slope. Traffic had loosened up, so I was able to speed up to highway speeds on the way down. Got stopped at a light and saw the "Engine Running Due to Temperature" warning, and the generator fired up and switched over. It only happened once, so I didn't get a photo, but it turned back off after a short while and swapped me back to battery mode. Didn't happen again during the drive.

Ambient temperature as read by the car: 107 degrees. Battery SOC at time of ERDTT: 4 bars.


I always thought ERDTT was just there for the defog requirements based on the tribal knowledge of this forum, but maybe there are rare scenarios when it is actually needed to manage the battery temperature.

My theory: hot as heck outside and lots of regen time due to MM engagement caused the battery to briefly get too hot. Note that I have driven at 70mph in 120 weather in range extended mode with no issues before.


(For you SoCal folks here was the route: 210W to 215N to 15N to 138N)
 

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here in florida where I live(east of Disneyworld a few miles from the atlantic ocean) for the last month we have had 105-110 degrees farenheight heat index.
the engine ecu automatically has the a/c circulating cold water thru the water jacket wrapped around the battery pack to help keep it cool.
when I plug my volt in to charge it at the end of the day you can here the engine fan start up to cool the battery while it charges it.
I can still get 10.9 to 11.0 kwh (53-56 ev miles) on a full charge
hopefully soon this sweltering heat will go away as more than a few people have had serious heat related problems
 

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ERDTT should not fire in hot weather. There is no reason for it. The cooling system is not aided by the gas engine.
Another possibility is an intermittent faulty temperature sensor in the battery making it think it's too cold.
That's what I'm thinking.
The AC is entirely electric, running the engine does nothing to help it.
I suspect the battery temp sensor had a transient fault. When the temp sensor fails, the temp reported to the car goes to -40F (which would make the car trip into ERDTT). A trip to the dealer is probably in order, to check the sensor. Mught just be loose, or high temps may be causing an intermittent failure.
 

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So it was not the ambient air temp sensor
 

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Discussion Starter #6 (Edited)
So, the statement in the manual regarding ERDTT and high voltage battery temperature isn't correct? Or, it's only regarding very low battery temperatures? (Wish it would state that if true - we dug the manual out while on the road and came to the conclusion it was normal behavior based on what it stated)

image.jpg

I assumed ERDTT ran to not to actively cool the battery, but to stop regen for a short while similar to what happens to folks when they start at the top of a long hill on a full battery. Someone once reported the engine will come on in that case as well.


I am not due at the dealer for a while, so I will see if it continues to occur
 

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This may fall under "We've got an on-board ICE. May as well use it." thinking.

It sounds like the battery could have been too hot for the BMS to keep up. Speculating that the ICE fired to give the battery a rest.
 

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So it was not the ambient air temp sensor
Good point it could be the ambient air temp sensor as well.

I don't think it would be to give the battery a rest. I would think PPR would happen in that situation.

107F is hot. But not that hot. Many Volts are run at temperatures hotter than that. This would be the first I have heard of an ERDTT at high temperatures. Now I know adding mountain mode adds a bit of a unique situation but there are lots of Volts that are run in mountain mode in the South Western US and it hasn't come up before.
 

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Speculating that the ICE fired to give the battery a rest.
Possible...
Heat is generated by charging OR discharging the battery. If the thermal management system was unable to get the temp down, starting the ICE would reduce the amount of power being drawn from the battery and so reduce the thermal load.

I'll be interested in hearing from WOT or someone with a deeper understanding of Volt programming or engineering.
 

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I think this might be the hot equivalent to the deep freeze 'engine running due to battery temperature' mode where the goal is to shift the energy load off of the battery until it is in operating temp range again, not so much for cabin temp.

Was the engine operating as normal (mostly fixed RPMs at 1-2 rates), or more in-step with vehicle load?
Or echoing the temp sensor hypothesis if not.
 

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Discussion Starter #12 (Edited)
I don't remember if the engine was operating any differently than normal. I was coming to a stop at a stoplight at the time of the notice, and it ended up being pretty short before it flipped me back to battery mode.

I tried to re-create it today by letting MM charge up about 3 bars, then burning it back off in Normal mode (ambient temp was reading the same 107 degrees), but no luck. My drive is mostly flat, so I can't recreate the long period of regen that happened immediately after MM had been running for so long in the hot weather.

I have made an appointment for my 45K service with Chevy at the end of the month, so I will mention it then. I doubt I will get a good answer from the service department unless they can see some faults from the temp sensor.

Does anyone think that temp sensor might have thrown a code? I could punch OnStar and ask for it if it did.
 

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Discussion Starter #13
OK, random update here. Came out to my car this morning to find it on the French Canadian language setting mysteriously. I have also been noticing inconsistent charging performance at night. If I am up late and in my kitchen, I can sometimes hear the car make the "charging" beep numerous times in a row.

So, I am beginning to think this might be a 12V battery going bad, since I have read those can cause all sorts of craziness.

Volt screen language.jpg
 

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That photo doesn't look like French. More like Hungarian or Slovak.

However, I do get switched to German language every now and then and it mostly happens while driving.
 

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Discussion Starter #15
Update: took my Volt into the Chevy dealer today. 12V battery was fine on the load test, and no faults noted with the onboard charger.

Chalking the ERDTT in hot weather to a mystery. I figure the charging issue is my Clipper Creek charger going bad at this point since the car charges fine on Level 1, and at public Level 2 stations. It's under warranty, so hopefully I will be able to get it replaced.
 

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That happened to me once and only once where it came up to what looked like a Slovak language. I hit English and it never happened again.
 
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