Temperature bars & real temps

[TomT]

Many seem to be forgetting one key point: The Tesla battery chemistry is different than that of the Leaf. It does not have to be kept as cool to prevent heat related degradation... Thus, comparing Telsa battery temperatures directly to Leaf temperatures is not possible and is misleading... A much better, but still far from perfect, TMS comparison would be the Volt...

I too was impressed at how little Tesla's TMS does in "normal" activity and modest temps (ie not Arizona).

 

[Weatherman]

Before everyone starts to dismiss active cooling as unneeded, the Volt, actually, does active cooling very well.

It will kick in when the battery temperature approaches 90 (which would still be 6 temp bars on a LEAF) and cools things down into the lower 70s. It doesn't have a significant impact on the battery range (as long as you keep it plugged so it can keep the battery cool until right before you leave). The battery is very well insulated, so it takes a long time to warm up. And even during the charge cycle, it only seems to increase the amount of energy required by about 10-15%.

After owning a Volt for a year, in a very warm climate, there has been no drop in EV range. I sure can't say the same thing about the LEAF. With the LEAF, I had already lost one capacity bar after only 11 months and a little over 8,000 miles. I'm about to lose the second bar any day, now, and I have less than 15,000 miles on the odometer.

 

[asimba2]

But do you have the luxury of having your Volt plugged in while you are at work? My coworkers with Volts drive in gas mode so they can leave enough charge (must be over 75%) for TMS to function on hot days while they at work.

 

[Weatherman]

I don't, but South Florida heat is "persistent warm" rather than "blazing hot". We, almost always, top out in the 90s, even during the summer months. Record high temps are around 100F. The battery seems to be well-enough insulated that temps in the 90s are not a problem.

Another thing to consider is that persistent warm temperatures can be just as damaging, if not more so, than extreme heat. Even if the Volt battery temp peaks in the mid 90s each afternoon, it's cooled back into the 70s on the drive home. The LEAF's battery stays in the 90s, day and night, for months on end.

 

[asimba2]

Another thing to consider is that persistent warm temperatures can be just as damaging, if not more so, than extreme heat. Even if the Volt battery temp peaks in the mid 90s each afternoon, it's cooled back into the 70s on the drive home. The LEAF's battery stays in the 90s, day and night, for months on end.

That is consistent with what I have seen on my Leaf. I go from the sixth temperature bar to the seventh on my way home from work. Due to the large thermal mass of the battery, it doesn't drop back down to the sixth bar until very late into the evening. It does-so quicker if I leave the car outside vs my garage with no air movement.

 

[RegGuheert]

It has been 103 degrees in Sacramento lately and for the last few days I have seen 7 temperature bars. The chart Tony posted says 7 bars show at 98.2 degrees F where the wiki says 117F.

That's not what the Wiki says. It says that if you have 7 temperature bars lit, your battery temperature is somewhere between 73F and 117F:

Battery Gauge Segment / Temperature Chart[4]:
Segments   Min Degrees C (F)   Max Degrees C (F)
12            56 (133)             none
11            52 (126)           59 (138)
10            49 (120)           56 (133)
 9             47 (117)           52 (126)
 8             36  (97)           49 (120)
 7             23  (73)           47 (117)
 6             10  (50)           38 (100)
 5             -3  (27)           27  (81)
 4             -5  (23)           15  (59)
 3             -8  (18)            4  (39)
 2            -12  (10)            2  (36)
 1            -15  (5)            -2  (28)
 0              none              -5  (23)

 

[davidcary]

Many seem to be forgetting one key point: The Tesla battery chemistry is different than that of the Leaf. It does not have to be kept as cool to prevent heat related degradation... Thus, comparing Telsa battery temperatures directly to Leaf temperatures is not possible and is misleading... A much better, but still far from perfect, TMS comparison would be the Volt...

I too was impressed at how little Tesla's TMS does in "normal" activity and modest temps (ie not Arizona).

Just a quick retort since you quoted me. What I said was that the issue isn't lack of a TMS but battery design - so I certainly wasn't forgetting that.

People seem to clamor for a TMS when perhaps the best solution is a battery design more like Tesla with no TMS. I think it is pretty obvious that a TMS would be helpful for the Leaf design and perhaps needed for the Volt design.

No real disagreement here, more just semantics. But from an efficiency standpoint, it is far better to just have a more robust design rather than rely on active cooling. Now upfront cost - that is a tough one. I think most people would agree that Tesla's battery is a bit cheaper per kwh than Nissan's. Which does make one want to buy TSLA.....

 

[asimba2]

That's not what the Wiki says. It says that if you have 7 temperature bars lit, your battery temperature is somewhere between 73F and 117F:

Battery Gauge Segment / Temperature Chart[4]:
Segments   Min Degrees C (F)   Max Degrees C (F)
12            56 (133)             none
11            52 (126)           59 (138)
10            49 (120)           56 (133)
 9             47 (117)           52 (126)
 8             36  (97)           49 (120)
 7             23  (73)           47 (117)
 6             10  (50)           38 (100)
 5             -3  (27)           27  (81)
 4             -5  (23)           15  (59)
 3             -8  (18)            4  (39)
 2            -12  (10)            2  (36)
 1            -15  (5)            -2  (28)
 0              none              -5  (23)

I really don't understand this chart. If 6 bars can be anywhere between 50deg and 100deg and the 7th bar is anywhere between 73deg and 117deg, what dictates a move from the 6th bar to the 7th?

 

[MikeinDenver]

That's not what the Wiki says. It says that if you have 7 temperature bars lit, your battery temperature is somewhere between 73F and 117F:

Battery Gauge Segment / Temperature Chart[4]:
Segments   Min Degrees C (F)   Max Degrees C (F)
12            56 (133)             none
11            52 (126)           59 (138)
10            49 (120)           56 (133)
 9             47 (117)           52 (126)
 8             36  (97)           49 (120)
 7             23  (73)           47 (117)
 6             10  (50)           38 (100)
 5             -3  (27)           27  (81)
 4             -5  (23)           15  (59)
 3             -8  (18)            4  (39)
 2            -12  (10)            2  (36)
 1            -15  (5)            -2  (28)
 0              none              -5  (23)

I really don't understand this chart. If 6 bars can be anywhere between 50deg and 100deg and the 7th bar is anywhere between 73deg and 117deg, what dictates a move from the 6th bar to the 7th?

I was thinking the same thing. Way too much overlap to be that useful.

 

[dgpcolorado]

^You may find the table on the first page of the thread more useful:
http://www.mynissanleaf.com/viewtopic.php?f=27&t=16631&start=5" onclick="window.open(this.href);return false;

That table came in the first edition of the service manual. It was later replaced by the table with the overlap. IIRC the theory behind the overlap is that as the battery ages and resistance increases the temperature bars will change when they light. But, yes, that table with huge ranges isn't helpful. And they wide ranges represented by the temp bars on the dash aren't very helpful anyway. Best to get a direct read from the battery temp sensors via a meter, such as the Leaf Spy application.

 

[abasile]

My coworkers with Volts drive in gas mode so they can leave enough charge (must be over 75%) for TMS to function on hot days while they at work.

That seems silly of them. The reason the Volt's TMS functions above 75% SOC, with the car off, is that the combination of high SOC and high temperatures causes more rapid degradation. At a lower SOC, TMS isn't so important. Plus, their battery packs are starting each day cool. Tell your co-workers they can drive on electricity!

 

[RegGuheert]

I really don't understand this chart.

I don't think anyone does. I'm not even convinced Nissan does.

 

[asimba2]

I really don't understand this chart.

I don't think anyone does. I'm not even convinced Nissan does.

Okay, at least it's not just me.