I did some additional testing with the prototype SOC meter, focusing on the range of charge from 1 bar down to the Very Low Battery warning. The motivation for this experiment was the consistent finding that a reading of 1 bar of remaining charge corresponds with a SOC percentage of about 25% on the SOC meter. At a recent breakfast meeting, we were discussing this unexpected finding.
Question at hand: If the SOC meter is going to be useful near the bottom of the range (which IMHO is the range where it is most critically useful), is the burn rate from 25% to 5% similar to the burn rate for the majority of the range of charge, or does the burn rate increase, i.e., does SOC "fall off the table" rapidly below 25%, leading a person using the SOC meter to overestimate their remaining charge, and therefore their remaining miles, at this point?
I started the experiment on July 20 at 1 bar and 25% SOC on the prototype meter. I drove around my neighborhood, in D mode, headlights on, AC off, on local highways and residential streets, stopping at lights and stop signs, and reaching perhaps 50 mph at times. This was not a steady speed run by any means. I recorded the SOC% and SOC number at every half mile and at the Low Battery and Very Low Battery alert points.
I've shown below the data that I already reported for my July 2 run, which was a smooth freeway run, along with the data from my July 20 run. I realize that the driving speeds and burn rate are different on a freeway run than with slower stop-and-go driving, with some regen happening at stop lights, etc.
I did a rough plot using Excel. The slope of the burn rate from the July 20 run from 1 bar down to Very Low Battery, appeared slightly steeper than the slope of the burn rate from the freeway run from 100% charge down to 1 bar, but it wasn't very much steeper. Of course, there might still be a faster burn rate from 1 bar down to 5% charge, but it was masked by the fact that I was driving stop-and-go with some regen.
Someone with better plotting skills than mine might want to plot this data and calculate the slope of the line from the two runs to see if we can draw any conclusions from it.
Code:
Miles Pct SOC# Alert and bars
0 99 279 12 bars
4.4 92 257 11 bars
9.2 84 236 10 bars
13.9 78 219 9 bars
20.8 71 199 8 bars
25.8 66 186 7 bars
35.1 58 163 6 bars
40.8 51 143 5 bars
51.7 36 102 3 bars
56.6 31 88 2 bars
61.8 26 73 End data collected July 2 (1 bar showing)
--------------
65.5 25 72 Begin data collected July 20 (1 bar showing)
66 25 71
66.5 25 70
67 23 67
67.5 22 64
68 22 62
68.5 21 59
69 19 55
69.5 17 50
69.7 17 49 Low Battery (last bar disappears, miles display starts flashing)
70 16 47
70.5 16 45
71 15 42
71.5 14 41
72 13 39
72.5 13 37
73 11 32
73.5 10 30
74 10 29
74.5 10 28
75 9 27
75.5 8 25 Very Low Battery
76 7 22
76.5 7 20
77 6 18
77.2 5 16 LEAF parked
