Time for Battery to Equilibrate with Ambient Temperature?

[Stoaty]

Now that we have a way to monitor battery pack temperature with the ELM327 and the android app by Turbo3, does anyone have any data on how quickly the battery pack equilibrates to ambient temperature. I know it takes a fair amount of time because of the thermal mass of the pack, but wanted to get an idea of the time frame. For example, if your Leaf is parked in the hot sun and the battery pack temp is 90 degrees F. and you move it to a parking garage where it is in the shade at 70 degrees F. how quickly does the pack reach the new temperature? A curve showing the temperature vs. time in this scenario would be very interesting. I can't check this myself as I don't have the ELM327 (yet).

 

[RegGuheert]

Here is a little bit of data from Phil:

I've noticed I can start out with a pack temp of 70, then take a long drive and return home with it reading only a few degrees higher, but still slowly climbing. It will continue to rise once the car is parked (even when inside a building with cool temps and not charging) and sometimes I've seen it get close to 80 before it starts to cool back off. This process takes hours because of the large thermal mass of the pack.

 

[JeremyW]

From this afternoon after L2 in the sun, quick charging and freeway driving at ~75mph:
1: 41.3
2: 40.6
3: 39.1
4: 38.3

After sitting for 4 hours in the shade with a light breeze and cooler temps:
1: 35.6
2: 34.2
3: 33.1
4: 30.7

Note all temps in degrees C.

 

[Stoaty]

After sitting for 4 hours in the shade with a light breeze and cooler temps:
1: 35.6
2: 34.2
3: 33.1
4: 30.7

What was the ambient temperature in the shade (roughly, if not known exactly)?

 

[tbleakne]

I am also very interested in determining the thermal time-constant of the battery. Thanks for your data, Jeremy. It indicates a shorter time constant than I have postulated.

Another useful experiment for those with the battery sensor readout would be to record the battery temperature before and after a Quick Charge. A QC represents a delta-function wrt battery internal temperature. Monitoring how fast the battery temperature returns to its pre QC level would yield the time constant.

 

[surfingslovak]

Interesting thread, look forward to learning more. On the topic of quick charging. Please note that the battery appears to cool a lot faster when driving per TickTock's post in the CANary thread.

 

[tbleakne]

Interesting thread, look forward to learning more. On the topic of quick charging. Please note that the battery appears to cool a lot faster when driving per TickTock's post in the CANary thread.

In this post TickTock says that battery discharge is endothermic and charge is exothermic which is consistent with my understanding.I have seen a graph for general Li chemistry that shows a dependence on SOC for both charge and discharge. IIRC the charge heating increases at high SOC and the discharge is reversed, switching from endothermic to exothermic as the charge declines. However, at modest to higher discharge power levels the endothermic characteristic of the chemistry is overwhelmed by ohmic losses in the conductors connecting the cells.

While driving electrochemistry is not the only process affecting battery temperature rise or fall. Air flow can be important, especially if the ambient temperature is significantly higher or lower than the battery temperature. Radiant heat transfer from pavement much hotter than the air to the bottom of the car may also be significant. Radiance goes as the 4th power of the absolute temperature, so this effect is much more important on hot days.

 

[Berlino]

Battery temperature just after driving at midnight according to LEAF Battery app: -4.1°C.

(Had been as high as +10.1°C earlier in the day after a full charge in a heated garage.)

External temperature: -21°C according to meteorological sites. Winds Under 10km/hr.
Overnight low: -23°C

LEAF battery warmer activated at 8:44am. External temperature -21°C, Winds Under 10km/hr.

Does the heater come on at -20°C, at -17°C, or at another temperature? I've since different temperatures stated.

If it's -20°C, I'm a bit surprised that it took less than nine hours to cover ~85% of the difference between the battery's initial temperature and the external temperature.

 

[Den]

Does the heater come on at -20°C, at -17°C, or at another temperature? I've since different temperatures stated.

If it's -20°C, I'm a bit surprised that it took less than nine hours to cover ~85% of the difference between the battery's initial temperature and the external temperature.

It comes on at -20C and off at -10C

Battery temperature just after driving at midnight according to LEAF Battery app: -4.1°C.

(Had been as high as +10.1°C earlier in the day after a full charge in a heated garage.)

How much "battery bars" were at these points?

 

[Berlino]

How much "battery bars" were at these points?

Sorry, I don't remember, I just use the battery app for temperatures.

 

[Goodtohave]

Past 3 weeks I have not seen the pack above 0 celcius on the dash display.

Last night my battery pack temp was at 0 bars, first time I have seen that. I preheated for 20 minutes and drove a half hour down to 70% before it went up to 1 bar. DD still at 0.

Does the elm get data below 0 from the Canbus? I am wondering if it is a limitation of the DD.

I will post some pics soon. -18 outside last night. Had the pack down to 70%, still would not regenerate when braking in ECO mode.

Battery measurements are weird in extreme cold. But car performs flawlessly. Kind of amazing!

 

[DaveEV]

LEAF battery warmer activated at 8:44am. External temperature -21°C, Winds Under 10km/hr.

How can you tell if/when the battery warmer turns on?

 

[Berlino]

How can you tell if/when the battery warmer turns on?

With MY13 you can configure Carwings to alert you to that.

 

[Den]

I will post some pics soon. -18 outside last night. Had the pack down to 70%, still would not regenerate when braking in ECO mode.

Wouldn't regenerate at all? :shock: Or just regenerates less than usually?

We still didn't have such temperatures this winter (we even still doesn't have any snow :/ ), but as I remember from last winter regeneration should work even at these temperatures, somehow very lazy couple of first kilometers, but then should work OK.

 

[tivollix]

no regen at all not one watt... Until the battery temps reach -10C.

 

[Den]

no regen at all not one watt... Until the battery temps reach -10C.

Hmm.. hope real winter will come finally here to check this (unfortunately did the sw upgrade at summer :/ ).