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Discussion Starter · #1 ·
I'm hitting the highway in a few hours, so wanted the pack as warm as possible to speed-up the first DCFC session, which I will hit after about 2 hours of driving. I thought I'd read that the Bolt heated the pack to a higher temperature when the Bolt is On or in Precondition, versus just plugged-in/charging. I was hoping to depart with a 20C pack (68F) .

Overnight, I left the Bolt plugged-in, set to Hilltop. This morning, I walked-up to the window and fired-up Torque. The "Batt Avg" temp was 57F, "Batt Coolant" 82F, and Batt Heat was 1256 watts. I think this is normal pack temp for "left plugged-in": about 15C pack.

I started the 15-minute precondition cycle. 22 minutes later, I came back. Precondition had finished. Batt Avg was up to only 59F (15C), and but Batt Heat was 0 Watts and Batt Coolant had dropped to 66F. I fired-up another precondition, but Batt. Heat did not come on. Pack temp stayed 59F.

15 minutes later, pack temp was still 59F, so I turned the Bolt On and sat in it. The Batt Heat stayed at 0w and pack temp is still at 59F. I turned the bolt off and did a 3rd precondition, also with no change. Pack is still 59F.

With pack avg. temp 59F, turning the Bolt On or Precondition does not seem to get the pack heater to kick-on. Pack heater behavior in Precondition+Plugged or On+Plugged seems to be identical to just Charging+Plugged or DoneCharging+Plugged.
 

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With pack avg. temp 59F, turning the Bolt On or Precondition does not seem to get the pack heater to kick-on. Pack heater behavior in Precondition+Plugged or On+Plugged seems to be identical to just Charging+Plugged or DoneCharging+Plugged.
Where are folks getting the idea that you can force the battery heater to come on by doing a cabin preheat? What is the the Batt Coolant Temp now? Is it at or below Batt Ave Temp?
 

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Where are folks getting the idea that you can force the battery heater to come on by doing a cabin preheat? What is the the Batt Coolant Temp now? Is it at or below Batt Ave Temp?
Maybe from Tesla:
When driving, heat is generated in the powertrain, which warms your car’s battery. For quickest charging experience, consider plugging into a Supercharger closer to your destination, to give the battery a chance to heat up. However, on occasions when this isn't convenient, precondition your car to start heating its battery before you leave.


Use Navigation in Your Car
Prepare your car for Supercharging by navigating to your destination, even if you know your route. When you enter a destination into your navigation in cold weather conditions and Supercharging is needed, your car will automatically begin to preheat your battery before arriving at a Supercharger to reduce charging time. Depending on the ambient temperature, and whether Preconditioning was used prior to departure, pre-heating the battery may take 45 minutes, or more.


For long-distance trips, we recommend starting your fast charging sessions at lower states-of-charge, when the battery is warm.
 

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Where are folks getting the idea that you can force the battery heater to come on by doing a cabin preheat? What is the the Batt Coolant Temp now? Is it at or below Batt Ave Temp?
It will do it if the vehicle is plugged in. It won't if not. I thought the temperature was 65F but I haven't had a chance to observe it this year, maybe it won't go that high on L2.
 

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The Bolt does not seem to be all that aggressive at warming the battery, unlike our 2015 Volt. I think your expectations for how warm the battery needs to be is the reason for confusion, at least based on my own observations.
 

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This post got me thinking, so I did a little test this morning.
A little background first, I bought this 2021 in June, so I haven't thought much about battery heating, and I don't have any prior data suggesting something has changed with this car, or something is wrong with it.

I plugged into my L2 EVSE last night with the car set to Target Charge to 75%. Don't tell anyone, but I charge the car in my garage over night.

This morning, after the car had finished charging, the garage was 47º. I plugged in my OBD dongle and using CarScanner, I found the battery temp was 48.2º. Hmm
Azure Font Slope Rectangle Electric blue


I used the app and ran the car through a pre-condition cycle. Watching CarScanner during the pre-condition I found a few odd behaviors. I had left the car parked with HVAC on, heat on. I wasn't surprised to see the heater switch on, but the A/C kicked on too, and ran for most of the warm-up period. I am not sure why, I double checked, and have Auto Defog off. More to the point, the battery heater never came on, and the Battery Temp never changed.

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I decided to try two more options. I usually leave my EVSE set to 16 Amps, and thought it might be limiting heat due to that. I cranked it up to 32 Amps, and tried a pre-condition from the key fob. I also turned off the HVAC this time. To my surprise, the cabin heat still switched on, even with the HVAC off. I thought I read late model Bolts don't run heat unless it is left on? Even weirder, the car ran the A/C through most of the pre-condition cycle. The battery heater never switched on.

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The last experiment method I tried was leaving the car plugged in, but starting it up and letting it sit. That did absolutely nothing. No HVAC, no battery heat.

So, when the heck does the battery heat switch on during pre-conditioning? Anyone have some data showing that? If this is normal behavior, the thermal management is even more abysmal than I thought
 

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This post got me thinking, so I did a little test this morning.
A little background first, I bought this 2021 in June, so I haven't thought much about battery heating, and I don't have any prior data suggesting something has changed with this car, or something is wrong with it.

I plugged into my L2 EVSE last night with the car set to Target Charge to 75%. Don't tell anyone, but I charge the car in my garage over night.

This morning, after the car had finished charging, the garage was 47º. I plugged in my OBD dongle and using CarScanner, I found the battery temp was 48.2º. Hmm
View attachment 38942

I used the app and ran the car through a pre-condition cycle. Watching CarScanner during the pre-condition I found a few odd behaviors. I had left the car parked with HVAC on, heat on. I wasn't surprised to see the heater switch on, but the A/C kicked on too, and ran for most of the warm-up period. I am not sure why, I double checked, and have Auto Defog off. More to the point, the battery heater never came on, and the Battery Temp never changed.

View attachment 38943

I decided to try two more options. I usually leave my EVSE set to 16 Amps, and thought it might be limiting heat due to that. I cranked it up to 32 Amps, and tried a pre-condition from the key fob. I also turned off the HVAC this time. To my surprise, the cabin heat still switched on, even with the HVAC off. I thought I read late model Bolts don't run heat unless it is left on? Even weirder, the car ran the A/C through most of the pre-condition cycle. The battery heater never switched on.

View attachment 38944

The last experiment method I tried was leaving the car plugged in, but starting it up and letting it sit. That did absolutely nothing. No HVAC, no battery heat.

So, when the heck does the battery heat switch on during pre-conditioning? Anyone have some data showing that? If this is normal behavior, the thermal management is even more abysmal than I thought
The battery operating at 48 degrees is fine, it's only really an issue when it gets down into the lower 30s, it's also best to keep it out of the upper 80s. The Bolts climate control system is downright pathetic as far as energy consumption, it loses heat under the hood, runs the AC most of the time the heat is on and makes zero attempt to reclaim heat from the transaxle or inverter.
 

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This post got me thinking, so I did a little test this morning.

If this is normal behavior, the thermal management is even more abysmal than I thought

This is exactly the behavior of our 2017 Bolt for over four years. The battery will heat when the battery itself is in the low 30s F. The HVAC dehumidifies, using the AC. Preconditioning is about the cabin, not the battery. The battery will only precondition based on its own temperature.
 

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Hmm, good to know. I always assumed pre-conditioning heated the battery to some value. Does anyone know the temp the battery heat turns on and what temp it turns off during pre-condition?
 

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Hmm, good to know. I always assumed pre-conditioning heated the battery to some value. Does anyone know the temp the battery heat turns on and what temp it turns off during pre-condition?

From memory, the battery coolant gets to 80s F, and pump continues to circulate the coolant until the battery sections get into the mid 60s F.
 

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If you want the battery warm, use the fastest L2 you can (32 amp for the 2017) and set your charging to finish just before your departure time. The battery may not be "warm", but it will not be "ice cold" if you do this. I did a bunch of experimenting with this when the car and torque pro were new to me, but I don't remember the details I had battery heating but I don't remember how it worked... and I am pretty sure it cut off when pack temp reached 60F, so the OP's not heating above 59F sort of makes sense. Try looking it up under my user name if you are interested.

Keith

<edit> found a relevant post, it wasn't about preconditioning, preconditioning has no effect as far as I can remember. It was about how charging affects battery temperature and heater behavior. If you leave the car plugged in, after the car reaches your charging setpoint the battery heater will kick on and cycle as needed until pack temperature reaches 60F. L2 charging speed has some effect on battery temperature, but not much compared to the battery heater when ambient temperatures are below freezing. Here is a link: L2 charge on cold soaked battery experiment. This thread has lots of good info about battery conditioning behavior.</edit>
 

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Discussion Starter · #13 ·
It will do it if the vehicle is plugged in. It won't if not. I thought the temperature was 65F but I haven't had a chance to observe it this year, maybe it won't go that high on L2.
I believe Wesley posted some data that after the Cold Weather Robustness fix, when he plugged into DCFC, the pack heater warmed the battery to 20C. I must have assumed that the same thing would happen when preheating/On while plugged in. But it's looking Iike both charging and preheat waem the pack to the same temp of 15C (on a 2017 with Final Fix).
 

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I believe Wesley posted some data that after the Cold Weather Robustness fix, when he plugged into DCFC, the pack heater warmed the battery to 20C. I must have assumed that the same thing would happen when preheating/On while plugged in. But it's looking Iike both charging and preheat waem the pack to the same temp of 15C (on a 2017 with Final Fix).
Did we ever get any confirmation that the "don't burn to the ground" software included the cold weather robustness patch? If not, then nobody has the cold weather robustness any more. Since the same patch was applied no matter what climate the owner lives in, I would suspect they did away with the cold weather robustness fix when the applied the battery fire software.

Keith
 

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Discussion Starter · #16 · (Edited)
Did we ever get any confirmation that the "don't burn to the ground" software included the cold weather robustness patch? If not, then nobody has the cold weather robustness any more.
I was out of warranty and unable to get it for free, so I never got it to begin with (probably would have been wasted money).

On my T-day trip, (11 DCFCs), I have screenshots of the following (note: Wesley’s cutoffs 15C=59F, & 20C=68F)
  • NO pack heat @58% SOC, 66F/68F pack/coolant temperature
  • 0 @68% 66/54
  • … next stop
  • 2kw @20% 43/59
  • 2kw @28% 48/72
  • 0 @43% 61/77 (maybe heat turned-off at 59F?)
  • 0 @57% 66/70 (pack is heating due to DCFC)
  • … next stop
  • 2kw @6% 63/54 (YAY! We have heating above 59F!)
  • 824w @17% 66/84 (tapering as we approach 68F?)
  • 0 @24% 70/61 (heat is off completely at 70F)
  • … next stop
  • [email protected] 5% 70/46 (pack is 70F but coolant is down to 46F from radiator!)
  • …next stop
  • 0 @12% 72/68
It looks like sometimes heating will come-on at low temp, and continue to 68F (tapers near the end). I think this means that the “final fix” may have included the “cold weather robustness” patch.

But other times, pack temp is between 59F and 68F, but heat is off (observed with SOC 58%, 43%, 57%). There may be other factors, like: the heater only starts below 59F, but once it starts, it will continue to 68F.

This would be a bit awkward: during each leg of your trip, you may actually hope that pack temp drops below 59F, so that the heater would raise it to 68F faster. If it only drops to 60F, maybe you get no heating at all during the DCFC session.

(regarding AC charging, that still never seems to continue above 59F, so maybe 59F is always the starting point of every road trip).
 

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I was out of warranty and unable to get it for free, so I never got it to begin with (probably would have been wasted money).

On my T-day trip, (11 DCFCs), I have screenshots of the following (note: Wesley’s cutoffs 15C=59F, & 20C=68F)
  • NO pack heat @58% SOC, 66F/68F pack/coolant temperature
  • 0 @68% 66/54
  • … next stop
  • 2kw @20% 43/59
  • 2kw @28% 48/72
  • 0 @43% 61/77 (maybe heat turned-off at 59F?)
  • 0 @57% 66/70 (pack is heating due to DCFC)
  • … next stop
  • 2kw @6% 63/54 (YAY! We have heating above 59F!)
  • 824w @17% 66/84 (tapering as we approach 68F?)
  • 0 @24% 70/61 (heat is off completely at 70F)
  • … next stop
  • [email protected] 5% 70/46 (pack is 70F but coolant is down to 46F from radiator!)
  • …next stop
  • 0 @12% 72/68
It looks like sometimes heating will come-on at low temp, and continue to 68F (tapers near the end). I think this means that the “final fix” may have included the “cold weather robustness” patch.

But other times, pack temp is between 59F and 68F, but heat is off (observed with SOC 58%, 43%, 57%). There may be other factors, like: the heater only starts below 59F, but once it starts, it will continue to 68F.

This would be a bit awkward: during each leg of your trip, you may actually hope that pack temp drops below 59F, so that the heater would raise it to 68F faster. If it only drops to 60F, maybe you get no heating at all during the DCFC session.

(regarding AC charging, that still never seems to continue above 59F, so maybe 59F is always the starting point of every road trip).
The robustness patch (now defunct) was not a warranty repair, it was a recall... anyone trying to get you to pay for it was scamming you. I have detailed posts about how to get them to apply it for free when they don't want too... but the point is moot.

The main improvement of the robustness patch wasn't heater use, it was charging speed in spite of having a cold battery. What charging speeds did you see on your adventures where pack temp was 43F and 48F?

Keith
 

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Discussion Starter · #18 · (Edited)
charge speed was slowwww.
DCC KW would start higher, then go down as the pack warmed (!).
Here's the charge speed dropping by 17% over 10 minutes of charging.

time, Batt Avg F/Batt Coolant F, Batt %DIC%, DCC KW

22:52, 43F/59F, 20.4% 25kw
22:54, 45F/63F, 22% 22.1kw
22:55, 45F/64F, 22.4%, 22.3kw
23:02, 48F/72F, 27.8%, 20.8kw
 
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