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Re: Cabin Air Cooling the Battery

Posted: Thu Jul 21, 2016 11:23 am
by knightmb
I just did some testing and it appears that the waste heat from the AC might actually work against this.
I started a L2 Charge at 15% SOC.
I put the Leaf in standby mode so I could activate the AC, set the Climate Control 72F at full fan power and vent outside air through both top and bottom vents. The outside ambient temperature at this time was 92F. I used LeafSpy to monitor the Leaf from my Office next to it and it was using 1,500 watts the entire time for the AC. I then recorded the T1 through T3 temperatures every 5 minutes with LeafSpy.

11:50AM
93.6 92.4 92.2

11:55AM
94.0 92.8 92.4

12:00PM
94.2 93.2 92.6

12:05PM
94.2 93.6 92.6

12:10PM
94.4 94.0 92.8

12:15PM
94.4 94.4 93.0

12:20PM
94.6 94.8 93.2

12:25PM
94.6 95.2 93.4

12:30PM
94.8 95.8 93.6

12:35PM
95.0 96.2 93.8

12:40PM
95.2 96.4 94.0

12:45PM
95.2 96.8 94.2

12:50PM
95.4 97.0 94.4

As you can see, there was a steady temperature climb for the whole hour. I then shut-down the AC in the Leaf and let it continue charging as it had reached 45% SOC by now. I then recorded the temperatures from this point via LeafSpy.

12:55PM
95.4 97.0 94.4

1:00PM
95.0 96.4 94.4

1:05PM
95.0 96.2 94.4

1:10PM
95.0 96.2 94.2

1:15PM
94.8 96.0 94.0

1:20PM
94.6 95.8 94.0

As you can see, the temperature started to decrease. I finally stopped after 1:20PM because I could already see the pattern. The ambient air temperature was actually up to 94F when I finished.

The AC was actually making the temperature rise and I suspect it is because the Leaf is designed to allow air flow from the front of the vehicle to out the back around the battery pack. With the AC running, the waste heat was being sent around the battery pack. The inside of the Leaf was nice and cold after I ended the AC test and it was using 1,500 watts the entire hour so I know it was doing max cooling allowed the entire time.

So I think any benefit from having the vent AC to cool the battery pack is defeated by the waste Heat produced by the AC since this air also flows around the battery pack. :(

Re: Cabin Air Cooling the Battery

Posted: Thu Jul 21, 2016 11:53 am
by Stanton
^ ^ ^ Nice test. Higher ambient temps (than @Danl) may also have a compounding affect: we all know that pack has a lot of mass.

Re: Cabin Air Cooling the Battery

Posted: Thu Jul 21, 2016 12:09 pm
by LTLFTcomposite
Here in FL we almost always run car ACs in recirculate mode because the humidity is so high the latent heat (if that is the correct term) of outside air coming in makes it nearly impossible to cool the car.

So this may explain why LEAFs in FL do so poorly.

Re: Cabin Air Cooling the Battery

Posted: Thu Jul 21, 2016 12:55 pm
by Danl
Stanton wrote:You are full of surprises @Danl! I don't remember this phenomena being discussed much way back, but there's one thing I would like to see (with all of your data actually): hotter ambient temps (like 100 degrees). If this method can drive a 7TB event to a 6TB event (or even lower), that would be a big benefit to the battery pack.

Yes, I would like to see that also.

Where I live we normally get a few days that hot, but not last year and so far not this year. So what is needed is people further south collecting data. If anyone can get the data log file from LeafSpy to me then I can get a chart like this back to them and also post it here.

Thanks,
Dan

Re: Cabin Air Cooling the Battery

Posted: Thu Jul 21, 2016 7:38 pm
by JejuSoul
Danl this is another great post. Thank you.

This should be the same in the Soul EV because cooled air will use the same exit pipe for air from the cabin as it uses for forced air cooling. Hence some cooling will occur before the battery temps get to 31C and the battery fan begins running.

Image

Re: Cabin Air Cooling the Battery

Posted: Fri Jul 22, 2016 9:18 am
by LeafMuranoDriver
knightmb wrote:I put the Leaf in standby mode so I could activate the AC, set the Climate Control 72F at full fan power and vent outside air through both top and bottom vents. The outside ambient temperature at this time was 92F.

Do you think the effect would have been greater if the AC was set to 60 instead of 72? Why set it to only 72?

Re: Cabin Air Cooling the Battery

Posted: Fri Jul 22, 2016 3:50 pm
by Danl
knightmb wrote:I just did some testing and ........ :(

Just sent you a PM. Can you send me the log file over regular Email?

Today I did the fan with the AC not turned on. That may be the right answer.

Thanks,
Dan

Re: Cabin Air Cooling the Battery

Posted: Fri Jul 22, 2016 3:51 pm
by Danl
LeafMuranoDriver wrote:
knightmb wrote:I put the Leaf in standby mode so I could activate the AC, set the Climate Control 72F at full fan power and vent outside air through both top and bottom vents. The outside ambient temperature at this time was 92F.

Do you think the effect would have been greater if the AC was set to 60 instead of 72? Why set it to only 72?

No, He had the AC running max already.

thanks,
Dan

Re: Cabin Air Cooling the Battery

Posted: Fri Jul 22, 2016 4:18 pm
by knightmb
LeafMuranoDriver wrote:
knightmb wrote:I put the Leaf in standby mode so I could activate the AC, set the Climate Control 72F at full fan power and vent outside air through both top and bottom vents. The outside ambient temperature at this time was 92F.

Do you think the effect would have been greater if the AC was set to 60 instead of 72? Why set it to only 72?

The AC can only use 1,500 watts when the vehicle is traveling less than 15 MPH (In parked included), so it wouldn't matter if I set it for 72 or 32, it will run the max cooling that it can until it reaches the set temperature. I did the test in blazing heat, so I never reaches a low enough temperature to start using less cooling power.

Re: Cabin Air Cooling the Battery

Posted: Fri Jul 22, 2016 4:23 pm
by knightmb
Danl wrote:
knightmb wrote:I just did some testing and ........ :(

Just sent you a PM. Can you send me the log file over regular Email?

Today I did the fan with the AC not turned on. That may be the right answer.

Thanks,
Dan

That would be great, it would use a lot less power. :mrgreen: