Cold Weather Observations

[rbort]

Oh yeah I missed that during my first waking moments and sips of my coffee which hadn't kicked in yet!

 

-=>Raja.

[larryh]

This afternoon the ICE remained off on the commute home.  The temperatures at the start and end of the trip were a couple of degrees warmer than yesterday:

 

Outside Temperature: 16 F

Coolant Temperature: 18 - 16 F

Transmission Fluid Temperature: 16 - 49 F

HVB Temperature: 30.2 - 44.6 F

HVB SOC: 57% - 23%

 

So maybe coolant temperature of 15 F is the threshold?

Edited November 18, 2014 at 11:53 PM by larryh

[rbort]

I drove in 9 degree weather last winter, I think the temp bottomed at 7 in Millis which is the coldest spot, my wife constantly reminds me of it (riding in the frigid cold) and the engine never kicked off.

 

Of course no heat no climate control just cracked windows and heated seats.

 

Today I drove in the low 30's nowhere near 9 but all EV anyways.

 

-=>Raja.

[openair]

This morning I drove for 8km in -12C (~10f), preconditioned to setting 18.5C (~65F) on 120v charger.  No other heating on the drive.  No ICE.

 

I suppose it's possible the preconditioning kept the engine and fluids warm enough for the whole 8km trip.

Edited November 19, 2014 at 12:30 AM by openair

[larryh]

Preconditioning warms the coolant.  Parking in a garage also keeps the car warmer.  The ICE does not usually start for the morning commute unless it is below 0 F.  Using the EBH in the morning allows me to drive the 8 mile commute to work in EV mode down to about -7 F.  It is the commute home, after the car has been out in the cold for 9+ hours, that causes the ICE to start.   It is the car's coolant/HVB temperatures that determine if the ICE starts.  It can be -20 F outside and the ICE won't start as long as the car is warm. 

Edited November 19, 2014 at 10:08 AM by larryh

[larryh]

As expected, the ICE came on again this morning in EV Now mode.  The coolant temperature was 10 F which is less than the 15 F threshold.  The car entered "Locked Electric Mode (L.E.M.) Override by Driver", the EV Now Icon on the display changed color to yellow, and the ICE came on after 1.92 miles.  The car actually entered the "L.E.M. Override by Driver" and the EV Now Icon on the display changed color to yellow for a short time earlier in the trip (shortly before 1 mile), but the ICE did NOT come on. 

 

The following chart shows the first 2.5 files of the trip.  The red line shows the Maximum Discharge Limit for the HVB (the maximum power output).  The green line shows the Maximum Charge Limit for the HVB (the maximum amount of power from regen that the HVB can accept).  The blue line shows the current power output from the HVB.  The purple line shows the PHEV mode of the car.  40 indicates EV Now and 50 indicates "Locked Electric Mode (L.E.M.) Override by Driver".

 

You can see the L.E.M. Override by Driver was entered just before 1 mile (the ICE did NOT come on) and again just before 2 miles (the ICE did come on).  It is expected the car will enter L.E.M. Override by Driver mode and the ICE will come on after about two miles when the coolant temperature is below 15 F.   However, it also enters L.E.M. Override by Driver mode when the Maximum Charge/Discharge Limits of the HVB fall below a threshold (in this case 15/45 kW).  The ICE may or may not come on at this time. 

 

It appears the battery is strained after periods of significant charge or discharge and needs to recover when the HVB is cold--the maximum charge/discharge limits fall.  For example, at about 0.8 miles, after completing acceleration from a stop and starting to cruise at constant speed, the charge/discharge limits fall.  Similarly, after slowing down using regenerative braking and beginning to speed back up again, at 1.2 miles, the charge limits falls slightly. 

 

Note that the Maximum Charge Limit increase gradually during the first 2.5 miles as the HVB warmed up from 14 F to 19 F.

 

 

Edited November 21, 2014 at 08:41 PM by larryh

[Fat Fusion]

I drove in 9 degree weather last winter, I think the temp bottomed at 7 in Millis which is the coldest spot, my wife constantly reminds me of it (riding in the frigid cold) and the engine never kicked off.

 

Of course no heat no climate control just cracked windows and heated seats.

 

Today I drove in the low 30's nowhere near 9 but all EV anyways.

 

-=>Raja.

 

Geez.  The outside temps drop below 55* and I turn on the heater.  Do you not heat your house either?

[rbort]

I do heat the house but I don't heat the car any more unless its plugged in a 240v station while I'm eating out and its already full (100%) then I might set go times to warm it up some though to be honest its not necessary.  I'd rather my EV range than a heated cabin.

 

Let's just say it works because I have not had to use gas since October 12th when I was on a trip to VT.  If I was running heat this past week in all the recent cold then for sure I wouldn't be still sitting pretty at 100% EV ratio.

 

-=>Raja.

[larryh]

The following chart shows the first 2.5 files of the trip.  The red line shows the Maximum Discharge Limit for the HVB (the maximum power output).  The green line shows the Maximum Charge Limit for the HVB (the maximum amount of power from regen that the HVB can accept).  The blue line shows the current power output from the HVB.  The purple line shows the PHEV mode of the car.  40 indicates EV Now and 50 indicates "Locked Electric Mode (L.E.M.) Override by Driver".

 

Note that the Maximum Charge Limit increase gradually during the first 2.5 miles as the HVB warmed up from 14 F to 19 F.

 

 

One more thing to note about this chart.  The power output of the HVB never exceeds the discharge limit and regen never exceeds the charge limit (note that positive power output from the HVB indicates traction and negative power output indicates regen).    Initially, the charge limit is 15 kW and gradually rises to 25 kW.  When it is warmer, the charge limit is 35 kW.  So when the HVB is cold, the HVB can't capture was much regen.  You can't slow down as fast when it is cold and still maintain a 100% brake score.  If regen exceeds the charge limit, the car will use the friction brakes.  It is harder to get a 100% brake score when the HVB is cold.   If you use Low when the HVB is cold, you will most likely cause the ICE to come on.  Low attempts about 25 kW of regen.  Since the HVB can't accept that much regen when it is cold, it will use the ICE instead to slow the car down.

Edited November 22, 2014 at 11:21 AM by larryh

[rbort]

Larry, try to charge the car to 90-95% instead of 100% and see if you can use L to slow down when cold.  I thought that the engine came on if you used L because the battery was full and that was the reason it cannot accept a high regen value.  Same thing goes for the brakes.

 

Try it on Monday and see if you see any difference in that.

 

-=>Raja.

[larryh]

The ICE will come on in Low or the friction brakes will be used, if you exceed the charge limit.  When the HVB is full, the charge limit is 0.  The charge limit is 0 anytime the actual SOC (not the displayed SOC shown by MFT) is above 98.5%  So you won't get any regen and the ICE will come on when you shift to L to slow down the car when the SOC is above 98.5%. 

 

The charge limit also depends on the HVB temperature.  If the HVB is cold, the charge limit will be low.  The friction brakes will be used or the ICE will also come when you exceed the charge limit.  The SOC does not play a factor in this case.  In my case, the SOC was well below 95%. 

 

So there are two reasons the ICE comes on or the friction brakes are used:   the HVB is too full or too cold.  This will most likely also happen if the HVB is too hot. 

Edited November 22, 2014 at 04:02 PM by larryh

[jdbob]

The Energi really needs a gauge that show actual regen power instead of just an up and down arrow. On the Tesla a dotted line is drawn on their gauge to show reduced regen availability due to a cold battery (or for other reasons I'm sure).

[murphy]

The obvious reason for no regen at all is if the battery is at 100% and a Tesla doesn't have any other way to provide back pressure except for the service brakes.

[jdbob]

The obvious reason for no regen at all is if the battery is at 100% and a Tesla doesn't have any other way to provide back pressure except for the service brakes.

 

Yes, if the battery is already at 100% you lose the regen. This is rare on a Tesla because normal daily charging is to 90% or less to save on battery wear. Also, the higher the charge the lower the current the battery can accept so getting a full charge can be tedious. For instance at 30% charge the car can accept 300 Amps but when up to 99% you will be down to less than 10 Amps.

[Hybridbear]

Larry - what was the temp of the HVB during that drive?

[larryh]

The temperature of the HVB ranged from 14 F to 19 F.  ETE begins to drop rapidly when the HVB temperature falls below about 20 F. 

Edited November 23, 2014 at 08:32 PM by larryh

[Hybridbear]

During a remote start event in winter I observed the heater drawing 4422.2 Watts to warm up the car. The HVB was discharging at a rate of 5.1 kWh during the remote start event. The DCDC converter was drawing about 700 Watts. This shows why preconditioning doesn't work on 120V. When plugged in to L2, the car can pull up to 3.3 kW which would give you a maximum of about 2700 Watts for heat if the fan & electronics require 700 W. On L1 you only have 1400 W total, that means you only have about 700 Watts for heat.

 

I figured I'd share the numbers which show why L1 doesn't do much to precondition the car.

[jetjam]

During a remote start event in winter I observed the heater drawing 4422.2 Watts to warm up the car. The HVB was discharging at a rate of 5.1 kWh during the remote start event. The DCDC converter was drawing about 700 Watts. This shows why preconditioning doesn't work on 120V. When plugged in to L2, the car can pull up to 3.3 kW which would give you a maximum of about 2700 Watts for heat if the fan & electronics require 700 W. On L1 you only have 1400 W total, that means you only have about 700 Watts for heat.

 

I figured I'd share the numbers which show why L1 doesn't do much to precondition the car.

 

 

How does that compare to the juice needed to precondition the car on a hot day?   Does the AC use less juice??

Edited November 25, 2014 at 01:53 AM by jetjam

[Hybridbear]

I've noticed in the Energi that right now in the winter the grille shutters always show up as being 12.9% open. Does anyone else experience that? In the warmer weather they usually showed up as 0% open except when the coolant would go above 200F.

[Hybridbear]

How does that compare to the juice needed to precondition the car on a hot day? Does the AC use less juice??

Less for AC.

[larryh]

I've noticed in the Energi that right now in the winter the grille shutters always show up as being 12.9% open. Does anyone else experience that? In the warmer weather they usually showed up as 0% open except when the coolant would go above 200F.

 

Yes--it is always 12.9%.  I'm not sure how accurate it is reporting the position of the shutters.

[Hybridbear]

Yes--it is always 12.9%.  I'm not sure how accurate it is reporting the position of the shutters.

But in warm weather it isn't. In warm weather is says 0.0. When we begin the day in the warm garage the shutters start out at 0.0, they cycle to 99.6 to test and then they close again back to 0.0. But after less than 5 minutes of driving they open to 12.9 as the temp drops with leaving the heated garage & going outside. I don't understand why the shutters stay closed in the hot summer but open in the cold winter.

[Russael]

You were on the hybrid forum for a long time.  I remember seeing a thread where people were putting a piece of plexiglass or some other clear, solid object in front of the grill and zip-tying it in place.  I don't suppose the hybrid had the same problem with the grill shutters keeping open a touch which is why the car ran inefficiently.  I remember people saying they had substantial mileage increases after blocking the (upper) grill completely.

[Hybridbear]

You were on the hybrid forum for a long time.  I remember seeing a thread where people were putting a piece of plexiglass or some other clear, solid object in front of the grill and zip-tying it in place.  I don't suppose the hybrid had the same problem with the grill shutters keeping open a touch which is why the car ran inefficiently.  I remember people saying they had substantial mileage increases after blocking the (upper) grill completely.

I don't recall the hybrid going to 12.9% open like the Energi does. I have also blocked the grille on the Energi. The issue is more about getting heat in the cabin than MPG. Without grille blocking it's very hard to get heat in the cabin because the coolant cools down so quickly.

[Hybridbear]

Yesterday morning while driving to Wausau with the outside temp in the low 40s I was able to turn on the heat as needed and the car just used the hot coolant from running the ICE on the freeway to give me heat. Today returning home the outside temp was about 45 and every time I tried to turn on a little heat the car would isolate the small coolant loop and run the electric heater. This would cause the coolant2 temp to drop from 185 (the temp of the overall ICE coolant loop) to about 130-140 while pulling about 1900 watts average load. While this loop was isolated the ICE loop would increase up to 190+F since less coolant was now circulating in that loop. As soon as I'd turn off the HVAC the system would stop separating the loops and return to overall 185F for the entire loop. 

 

Why in the world would the car behave this way? Doesn't it know to use the hot coolant from the ICE when it's on? 

 

The only difference I can think of is that when I left home on Wednesday I had plugged in the block heater overnight so the coolant was already hot before the ICE turned on the first time. This morning the coolant was under 40F to start the day and when I left work to come back to MN the heater loop was at about 140 from remote starting the car while the ICE loop was only about 45F (ambient temp). I did not turn on any heat until after the entire loop showed 180+F. Could the different starting temps have caused this? I did not shut the car off the entire trip home so I wasn't able to restart and test to see if that improved matters.

This happened again today. I think that it happens when the ICE coolant is cold and you remote start the car in EV Now which heats up the small coolant loop. Then you switch to EV Later while driving and even when the coolant gets hot the car still wants to use electric heat only. I don't understand why it does this, but I think I have figured out why it happens.