RegGuheert
Well-known member
Agreed.Nubo said:dsh said:I wanted to make a comment regarding my lost capacity bar just a few days ago. Prior to losing the capacity bar(Now have 10 vs. 11), I noticed my temperature bars totaled 6. After losing a capacity bar, my temperature guage now shows 7 bars.
Correct me if I wrong but, it seems the more the batteries are degraded due to heat, the hotter their temperature becomes...Does that mean they are working 'harder', thus are now giving off more heat?
My understanding is that yes, as the battery degrades its internal resistance increases = more internal heat generation.
I'm not too confident in Nissan's prediction of a declining rate of degradation. First, because of the aforementioned increase in heat generation which makes a bad situation worse. Second, because an owner trying to maintain the usefulness of the car will begin to use a greater percentage of SOC. Meaning more frequent charges, more charges to 100%, deeper discharges.
In a lab the batteries might show a declining rate of degradation. In the real world people will work them that much harder.
Also note that it seems that according to the service manual as the battery degrades Nissan adjusts the meaning of the bars as a function of temperature:
(Please note that I have interpreted the graph so that the range values can be read as numbers.)RELATIONSHIPS OF THE NUMBER OF LIGHTING SEGMENTS OF LI-ION BATTERY TEMPERATURE GAUGE AND LI-ION BATTERY TEMPERATURE
0 Bars: Up to -5C (23F)
1 Bar: -15C (5F) to -2C (28F)
2 Bars: -12C (10F) to 2C (36F)
3 Bars: -8C (18F) to 4C (39F)
4 Bars: -5C (23F) to 15C (59F)
5 Bars: -3C (27F) to 27C (81F)
6 Bars: 10C (50F) to 38C (100F)
7 Bars: 23C (73F) to 47C (117F)
8 Bars: 36C (97F) to 49C (120F)
9 Bars: 47C (117F) to 52C (126F)
10 Bars: 49C (120F) to 56C (133F)
11 Bars: 52C (126F) to 59C (138F)
12 Bars: 56C (133F) and above
Note:
- Li-ion battery temperature gauge shows Li-ion battery temperature by correcting it according to the battery capacity. Consequently, the number of lighting segments of Li-ion battery temperature gauge can be different regardless of the same Li-ion battery temperature.
- This graph shows corrected temperatures. These to not agree with the CONSULT temperature shown in data monitor item "BAT TEMP".
Note the text in the first note. I am not at all sure what "correcting it according to battery capacity" means but perhaps they are attempting to calculate the temperature inside the cells by using a crude thermal model and adjusting losses in the battery based on degradation information. That would imply that they might show more temperature bars after the battery degrades than they did when it was new for the same temperature..