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"Vehicle Systems Very Hot. Charge Speed Reduced"

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Ugliest1

S85: "Sparky"
Supporting Member
Aug 19, 2013
1,401
1,661
Victoria BC Canada
This is a new one on me, and from the sounds of it was a new one on the Tesla support person I talked to. Thankfully everything on the car continued to appear to work normally, and Tesla couldn't see any problem from their end.

Yesterday we were driving from Palm Springs / Quartzsite to Kingman, in 38-42C (100+F) in Range mode and being very comfortable in the AC the car was providing us. 15 miles out of Quartzsite we ran into (not literally) stopped traffic on 10E because of an accident involving a pickup towing a trailer full of hay bales, and a Fed Ex truck. We stopped, and sat for 1hr 20 min before traffic started moving again. We left the car in Range mode throughout, with AC going. Once we got to Kingman, I plugged in and everything looked normal at first. But quite quickly the following popped up on my display: "Vehicle Systems Very Hot. Charge Speed Reduced" (see pic).

I phoned Tesla service, they suggested unplugging, powering down the car completely, wait 20 sec, then power up and re-start charging. No change - message was on there immediately. Rebooting both screens didn't change anything; no other outward sign of problem so we continued on charging to get our planned amount and left for Laughlin. It was about 10-15 minutes down the road at ~65mph that suddenly the warning message cleared and ... Bob's your uncle. There didn't seem to be any other option to actually try to deal with the "overheating". I felt powering down and waiting a while would be worse because then the normal cooling would also stop.

I had just had the sound insulation installed to quiet the AC, was wondering if that kept some heat in as well. Things in the frunk were quite hot once we stopped. I've never seen this mentioned on TMC and a search only brought up a Roadster. Any comments?
 

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This is not good. Those of us in Hong Kong spend half the year in bumper to bumper traffic 33°c and 95% humidity. We'll probably get this all the time.

?

This isn't the first Model S to be stuck in traffic during a particularly hot day, so don't make the assumption that it's some horrific omen for Hong Kong or even that it had anything specific to do with bumper to bumper traffic, or that it was hot out.

Don't people ever get tired of blowing things out of proportion, particularly when they don't have any specifics?!? This is the first time I've ever read about such an incident with a Model S. Let's just wait to see what Tesla finds out before we make such broad assumptions.
 
If you look at the picture, even in the reduced charge speed, you were getting 64 kW with 158 rated miles in the battery. That's over 180 mph charge rate; the car is still doing very well. I am sure that a lot of the Supercharger power was running the heat pumps at max. The problem for the heat pumps when you are stationary (on a stopped highway or charging) is that the only air flow over the condenser coil (hot side) is from the cars fans. Less air over the condenser coils and they getting hotter, reducing the heat pump efficiency and capacity. I assume the fans were running pretty hard. Once you started moving, the ram air from the MS speed added to the car's fans started to cool things down as you drove away; in addition, it takes a lot less than 64 kW for steady speed on the highway. The reduced power put less load on the heat pump.

Range mode cooling probably lets the battery drift to near it's maximum operating temperature. The added waste heat of charging the battery probably pushed the battery temperature over some limit. This was a pretty extreme test. It would be interesting to see what happens without range mode on the heat pump.

It seems to me the car protected itself and performed great under the conditions. I rode my bicycle across that desert, many, many years ago, when it was 47˚ C. Those kinds of temps stress all systems...
 
What concerns me is the OP just had the sound insulation installed. I was already concerned what this might do to the heat pump's efficiency before reading this post. I'm scheduled to have this done in a few weeks... Hmm.
 
Range mode cooling probably lets the battery drift to near it's maximum operating temperature. The added waste heat of charging the battery probably pushed the battery temperature over some limit. This was a pretty extreme test. It would be interesting to see what happens without range mode on the heat pump.

But he was at a supercharger. Seems to me the car should be smart enough to switch the coolant pumps into high gear and disregard the range mode setting. I've never used range mode before and this scenario is just another reason why I don't think I'll ever use it unless there is some extreme scenario in which I need the range. It is my experience that the A/C doesn't use a whole lot of power even without range mode.

Still, with ~60% SOC if you're getting 64 kW that's pretty good by any measure. My guess is there wasn't much of a reduction at all.
 
I'm not worried about this. It was just telling you (probably unnecessarily, if it makes people feel uneasy), that charge speed on the Supercharger was being reduced due to high system temperatures. The sound insulation could have had something to do with it, and likewise the range mode could have had something to do with it (it is very possible that the car's battery would have been cooler had you not had range mode on). Or this is a new message from the latest software release, and the car always did this, but never told you.

Anyways, you were pumping 64 kW into the car, which is a fair bit (more than the fastest Chademo fast charger) on a very hot day after a long time with no air flow. Unusual circumstances.

And in the end, the car continued to charge and continued to run just fine.
 
I supervcharged in Quartzite, Kingman, Flagstaff and Buckeye yesterday, all times same message, think how hot the battery was from 150 degree asphalt and charging, definately too hot.
It caused me no problems either and went away soon after driving each time.
 
Thanks all. Let me reiterate I couldn't see anything wrong with the car's performance throughout and I didn't mean to imply that suddenly there's something wrong with all cars. Like Cottonwood said, the car seemed to protect itself just fine (thanks Cottonwood for the explanation... I was thinking along those lines but didn't have the tech knowhow to work the logic through thoroughly... thus the post).

I used range mode yesterday because of our mileage needs over yesterday and today with no further charging available after Quartzsite before finally getting to Vegas on our roundabout overnight route. I hadn't used it before and will likely not use it again except for specific circumstances. By the way the car performed fabulously.

Re the A/C sound dampener, all things considered I am very happy to have gotten it. It reduces the noise quite a bit, and the rest of the car's systems seem to take care of other side effects.

Vger - yup I'm sure! And even though the car must have been shocked by all the non-Victoria sun and heat, we felt totally comfortable ensconced in our little noiseless, vibrationless, oilless cocoon.

Ok, next question: How on earth did Tesla manage to get SO MANY THINGS right!!?????!?!?!??!?!?

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Did you have range mode enabled as well when the message appeared?
Yes, once I saw the message (while supercharging), I took range mode off as I was wondering if that had escalated things a bit. But that wouldn't have made any difference (I am assuming) until we started going again.
 
I supervcharged in Quartzite, Kingman, Flagstaff and Buckeye yesterday, all times same message, think how hot the battery was from 150 degree asphalt and charging, definately too hot.
It caused me no problems either and went away soon after driving each time.
Out of curiosity, what firmware are you on? I'm on 5.11(1.59.47), installed this past Tuesday at Palm Springs SC.
 
I have done that trip many times. Recently in the same heat (around F 108 degree). Never got that message. Question: did you hear the AC pump running full speed when you charged at the Supercharger? I think once you plug in at a Supercharger, you have plenty of power so I would assume *if* the battery is too hot, the car will use all it's available power to cool it down if it's too hot.

I'm not sure why people assume range mode would let the battery go hot. As far as I understand range mode limits the cabin AC and heater in certain ways, but I doubt it would let the car overheat. I used range mode quite a bit on my way back and forth between Los Angeles and Phoenix, in extreme heat. What I noticed is that the AC will cool just fine as long as you drive with low power consumption. Once you go uphill and need more power, the cabin AC will be reduced. Once you go downhill or just normal, the AC cools down more. I can totally feel the difference in cabin temperature depending on how much power the motor needs.

Tesla always said that the power at a Supercharger might be reduced at temperatures over 100 degree. So it seems it's not unexpected and nothing dangerous and harmful to the car. 65 kW at 50% SOC is actually still very good.
 
Turning off range mode would probably have fixed (or possibly prevented) it.

Range mode limits A/C power, and the A/C is redirected to the drivetrain when it gets hot. The combination of sustained power in high heat, followed by sitting in traffic with high heat (no airflow), followed by Supercharging would seem to be a good combination for getting this message.
 
I'm not sure why people assume range mode would let the battery go hot. As far as I understand range mode limits the cabin AC and heater in certain ways, but I doubt it would let the car overheat.

In the winter, range mode limits the heating of the battery pack. I would think that in summer it would also limit the cooling as well. I try to remember to turn range mode off when charging. When it's cold and I forget, the battery is not completely warmed up. If I remember it's completely warmed up. Tesla should fix the software to automatically disable range mode when the car is plugged in.

I don't have any summer range mode observations because I've found that it really doesn't help in summer (when compared to just adjusting the temperature setting up and down as required).

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Technical Service Bulletin. This is a fix that is applied when a customer complains rather than a fix that is pushed out to every car as they come in for service.
 
I'm going to go out on a limb here and say that Tesla is not going to allow any modes the car allows an owner to select are going to have detrimental effect on the battery pack.

Yes range mode limits A/C performance for cabin cooling... but they aren't going to allow you to cook your battery. Yes, that mode will not heat your battery as aggressively in cold weather, but a cold has no harmful effect on the pack... getting too hot does.

Deciding not to use range mode in the future as a result of an informational message where the car seemed to be managing itself as designed seems a bit premature.

I'm also going to suggest compressor shroud had little to do with it either....