Li-On Temperature bar tutorial, please

I am confused about the temp bar, its issues and the import of it.

I though 5 and 6 in the battery temp bar was OK, and 7 was a danger zone.

I have routinely had 5, or so I thought, until all the AZ talk and I started watching it more this summer. I get 5s and 6s, mostly 6s during the day and drive home.

can folks clarify, or is this something we are all speculating about as Nissan has provided little guidance?
of course, the manual is very inspecific about this. it says anything in the middle is good.

I remember using "5's"...
The 5th bar starts at 50°F
And it is almost 5x5 = 25 degrees wide (or 24.4 or something).
Bars 4, 5, 6, and 7 are all the same width.

So, bar 4 goes from about 25+ to 50.
Bar 5 from 50 to 75- (really to 74+)
Bar 6 from 75 to 100 (really 74+ to 99-)
Bar 7 from about 98+ to about 122.

Generally, it appears that the hotter the battery pack,
the faster it "ages" (losing capacity).

so 5 is optimal

4 or less stores less capacity for no permanent long term damage
6+ is not good and does cause long term damage. the higher the #, the faster the damage. generally 6 is pretty mild.

thanks.
so the transitional temperature line is about 75 degrees between 5 and 6 bars.

the garage at work is above 75 degrees. maybe I will move to the lower level and walk up an extra flight.
it is cooler down there.

what is this chart's source?
the shop manual?

LEAF battery temperatures for a new, not degraded battery.
Source: Nissan Service Manual

Segments Degrees C (F).     Temp difference 
12----------60---------(140).........4.5F
11----------57.5-------(135.5)......4.5F
10----------55---------(131).........4.5F
9-----------52.5-------(126.5)......4.5F
8-----------50---------(122)........23.8F
7-----------36.8-------(98.2)......23.9F
6-----------23.5-------(74.3)......23.9F
5-----------10.3-------(50.5)......23.9F
4----------/ -3---------(26.6).......5.4F
3----------/ -6---------(21.2).......5.4F
2----------/ -9---------(15.8).......5.4F
1----------/-12--------(10.4).......5.4F
0----------/ -15---------(5).........5.4F

Battery heater activates (if equipped) at -20C

so, as the battery degrades, you see fewer 6s and 7s; because the threshold temperature is higher.
OK.

The problem with the temperature bars is that they are way too coarse to give us the information we would like. Thus:

"Low" 6 temp bars - 76 degrees, pretty darn close to optimal
"High" 6 temp bars - 94 degrees, not good for battery, will double the rate of battery capacity loss (difference of 18 degrees F. = 10 degrees C.). compared to 76 degrees.
"Low" 7 temp bars - 99 degrees, not good for battery, just a bit worse the "High" 6 temp bars.
"High" 7 temp bars - 117 degrees, really bad for battery, quadruples rate of battery capacity loss (difference of 36 degrees F. = 20 degrees C.) compared to 76 degrees; on the edge of voiding warranty if prolonged (Leaf 24 hours in 120 degree ambient temp)

As you can see, we need much finer gradations to get meaningful information about how hot the battery is getting (and staying). That's why we want the LeafScan!

It appears that garygid, EdmondLeaf, and TonyWilliams are all quoting from the first edition of the LEAF Service Manual. That table was removed in the second edition (April 2011) and replaced by a bar graph which shows much wider ranges depending on battery degradation. RegGuheert did some interpolations of the second edition graph and came up with a very different set of numbers which I put in the Battery, Charging System section of the Wiki after checking that his numbers agree with what I see in the graph.

Note that in the original table it was not clear whether the numbers were "bar off" trigger values or "bar on" trigger values so, with a new battery, 6 bars could have been either 51F-74F, or 74F-98F. Frankly, I think most people have been reading that incorrectly, including three statements above in this thread. There is no doubt in the new bar graph as to which range goes with which number of bars, so I showed possible temperature ranges based on the number of bars currently showing. What is not clear in the new graph is whether the transition points are adjusted upward or downward as the battery ages. But the full table EdmondLeaf showed (which I hadn't seen before) clearly has transition points moving upward with battery degradation.

If so, RegGuheert's numbers would suggest that 6 bars in a new battery is really about 50F-73F.

Ray

planet4ever said:

If so, RegGuheert's numbers would suggest that 6 bars in a new battery is really about 50F-73F.

Click to expand...

Common sense tells me this can't possibly be so. My parking garage generally runs 60-70 degrees F. I almost always see 5 temperature bars when Leaf has been in garage for a period of time. Yesterday, my Leaf had 5 temperature bars, garage temp about 70 degrees F. I took it out for a few errands (ambient temp outside was 75 degrees in the shade) and in about 30 minutes it showed 6 temperature bars). My battery has about 6% capacity loss. Temperature bar changing to 6 right at the expected junction (74 degrees F.)

deleted

Using temp logger located by emergency disconnect my experience is that TB 6 starts at 74F and go back to TB 5 at 72F. I did measure that quit few times to see if logging by emergency disconnect is good indication of battery temp. Used 74F (switch from TB 5 to 6 and back) as my reference point.

EdmondLeaf said:

Using temp logger located by emergency disconnect my experience is that TB 6 starts at 74F and go back to TB 5 at 72F. I did measure that quit few times to see if logging by emergency disconnect is good indication of battery temp. Used 74F (switch from TB 5 to 6 and back) as my reference point.

Click to expand...

this sounds reasonable and roughly correlates to what i have seen. i kinda thought the switch to 6 TBs would be higher (i was guessing 76-80) but the switch back to 5 being nearly the same (70-72)

now i did not use any measurement other than thermometer in garage and the fact that our Summers generally run right at the temp where 5 and 6 switch

Stoaty said:

planet4ever said:

If so, RegGuheert's numbers would suggest that 6 bars in a new battery is really about 50F-73F.

Click to expand...

Common sense tells me this can't possibly be so. My parking garage generally runs 60-70 degrees F. I almost always see 5 temperature bars when Leaf has been in garage for a period of time. Yesterday, my Leaf had 5 temperature bars, garage temp about 70 degrees F. I took it out for a few errands (ambient temp outside was 75 degrees in the shade) and in about 30 minutes it showed 6 temperature bars). My battery has about 6% capacity loss. Temperature bar changing to 6 right at the expected junction (74 degrees F.)

Click to expand...

I agree. The reason that I like the chart in the first edition of the service manual is that the tipping points for four/five and five/six bars are nearly identical to what I've observed with my garage ambient temperatures. So that chart seems more useful to me.

What I don't get is why Nissan changes the temperature scale as the battery degrades? I can't fathom why they deemed that change in temperature bars useful. It would have been nice if they had just given us the actual battery temperature (an average of the sensors would be fine) rather than the obscure bars.

dgpcolorado said:

Stoaty said:

planet4ever said:

If so, RegGuheert's numbers would suggest that 6 bars in a new battery is really about 50F-73F.

Click to expand...

Common sense tells me this can't possibly be so. My parking garage generally runs 60-70 degrees F. I almost always see 5 temperature bars when Leaf has been in garage for a period of time. Yesterday, my Leaf had 5 temperature bars, garage temp about 70 degrees F. I took it out for a few errands (ambient temp outside was 75 degrees in the shade) and in about 30 minutes it showed 6 temperature bars). My battery has about 6% capacity loss. Temperature bar changing to 6 right at the expected junction (74 degrees F.)

Click to expand...

I agree. The reason that I like the chart in the first edition of the service manual is that the tipping points for four/five and five/six bars are nearly identical to what I've observed with my garage ambient temperatures. So that chart seems more useful to me.

What I don't get is why Nissan changes the temperature scale as the battery degrades? I can't fathom why they deemed that change in temperature bars useful. It would have been nice if they had just given us the actual battery temperature (an average of the sensors would be fine) rather than the obscure bars.

Click to expand...

probably the same reason the delta is ridiculously large. to create confusion.

the bars are obviously controlled by some other entity than a standard temperature probe.

i am guessing resistance, voltage also play a part

Stoaty said:

planet4ever said:

If so, RegGuheert's numbers would suggest that 6 bars in a new battery is really about 50F-73F.

Click to expand...

Common sense tells me this can't possibly be so. My parking garage generally runs 60-70 degrees F. I almost always see 5 temperature bars when Leaf has been in garage for a period of time. Yesterday, my Leaf had 5 temperature bars, garage temp about 70 degrees F. I took it out for a few errands (ambient temp outside was 75 degrees in the shade) and in about 30 minutes it showed 6 temperature bars). My battery has about 6% capacity loss. Temperature bar changing to 6 right at the expected junction (74 degrees F.)

Click to expand...

I can certainly see your point, but common sense also says that your interpretation of the original table can't be possible. If 74°F is the minimum for 6 bars, then 5°F is the minimum for 0 bars, meaning that you would not be allowed to start the car if it had been sitting outside for some time at zero degrees. That hardly seems likely. On the other hand, if 74°F is the maximum for 6 bars, then you lose the last bar at 5°F, and 140°F is the maximum for 12 bars, meaning that you would not be allowed to start the car if the battery temperature was 140°. This makes lots of sense.

OK, so we have two interpretations, and neither of them seem to be possible. Please note that my statement started "If so," and the condition was that the transition points start at the low end of the ranges shown in the graph, and move upward as the battery ages. The only justification I have seen for that is that the first edition table Nissan removed showed that happening. So let's think some more about this:

dgpcolorado said:

What I don't get is why Nissan changes the temperature scale as the battery degrades?

Click to expand...

Why indeed? Could it be that a degraded battery becomes less sensitive to heat, so can be run hotter without further damage? If so, they could raise the bars, on the assumption that we would be thinking "6 bars is OK, 7 not so good." But, help me out here, some of you battery chemists, I wonder if a degraded battery might not become even more sensitive to heat, so the Nissan engineers would want to warn us earlier by lowering the transition points. If the transition points actually start at the high end of the ranges, then 5 bars in a new battery would go up to 81°F and Stoaty's observations with a slightly degraded battery could be right on.

It's the wrong time of the year to ask this, unless we have a reader in southern Chile, or possibly (if it gets colder than I think) in the mountains southwest of Canberra, but have any of you cold weather folks tracked your battery temperature bars against the car's temperature during the winter? Do you really see 2 bars if the car sits outside starting at about 10°F (-12°C), or does it have to be more like 28°F (-2°C)? Have you ever tried to start the car after it had been sitting at less than 5°F (-15°C)?

Ray

planet4ever said:

I can certainly see your point, but common sense also says that your interpretation of the original table can't be possible. If 74°F is the minimum for 6 bars, then 5°F is the minimum for 0 bars, meaning that you would not be allowed to start the car if it had been sitting outside for some time at zero degrees. That hardly seems likely.

Click to expand...

I think data (observations) should always trump some hypothetical situation. All observations agree that the transition point is about 74 degrees F. for a new(ish) battery.

If we can discover how to read the Battery Pack temperature(s) from the LEAF's CAN bus,
then the SOC (GID) Meter could possibly be updated to display this very useful information.

Maybe somebody who is friends with a Nissan tech-person, with access to a Consult III+
device, could determine how to read the four Pack temperatures?

Anybody willing to try?
Asking politely is unlikely to cause a problem.

We have no actual data that indicates that the 5th Temperature Bar is not 50°F to 74°F
for a new battery.

The little data reported indicates that about 74°F is indeed the temperature where
we observe 5 Bars changing to 6 Bars, again, for a "new" battery.

Does anybody have actual data that disagrees with this?

Probably for the same reason that they won't give us actual SOC...

dgpcolorado said:

What I don't get is why Nissan changes the temperature scale as the battery degrades? I can't fathom why they deemed that change in temperature bars useful. It would have been nice if they had just given us the actual battery temperature (an average of the sensors would be fine) rather than the obscure bars.

Click to expand...