Just to add to herode10's comments from a few months back, I've collected data from a repeat of a 300 km drive going from 90% down to 15%. This time I've logged the Ah (coulomb) registers as well so I could plot Ah as well as energy against SoC. It's pretty clear now that SoC follows Ah more closely than kWh and that meshes with my experience on this round trip where I noticed a greater rate of loss in SoC as I approached 15%. The plots are not about driving efficiency, rather they are more about if the SoC reading correlates linearly to energy remaining. For what it matters battery temp ranges from 11 to 22°C, noting that it's a sunny day but still the middle of winter.
The upper two lines are cumulative net Ah out of the battery plotted against SoC displayed and BMS respectively. The lower lines are cumulative net energy out against the two SoCs, with a correction of returned regen energy to accommodate normal battery loses. All four lines have linear trendlines overlaid with the slopes noted. It's hard to see in the image this forum renders but the linear trendlines fit the upper lines somewhat better than the lower.
As we've noted before the slopes of the upper Ah line (1.805 x 100) and upper energy line (0.639 x 100) closely match the 180 Ah and 64 kWh battery pack ratings, respectively. This should allay speculation that the usable capacity is less or greater than advertised.
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The second plot is how I determined the cumulative battery cycle efficiency of 98%. Once every charge cycle the CDC and CCC (colulomb) counters pass each other. Coulombs don't disappear as losses like energy does so they will match every time a certain SoC is passed, which I would assume matches the battery state when the counters were zeroed. Here I have all four odometers plotted over 90% down to 15%. As I pass through 55% SoC(disp) the charge and discharge coulombs match and at that point the ratio of the energy counters will reveal the cycle efficiency achieved since these counters were zeroed. That would be at the 196 update I had in Dec 2020.
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This plot is the cell voltage while driving compared with LG's definition of "open cell voltage" vs SoC for a new cell.
There are two caveats here: One is that, while driving the voltage is all over the place and is certainly not "open circuit". It sags on power and rises on regen. The second is that we don't know if the SoC(BMS) matches LG's published definition of SoC. It appears that it may match but even though that's probable, it's not certain. The matching of the black 15% moving average curve to the blue LG spec does somewhat support this conclusion.
In this plot of 2590 data points you'll note that the peaks (during regen) are narrower than the sags (while powering up hills), because they are plotted against SoC rather than time. The SoC doesn't drop much on downhills so the data stays horizontally compressed.
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One last plot, the red dots show 12V system voltage every 5 seconds over the same trip. The point here is that the 12V battery does not have a good opportunity to charge while driving, however it is not allowed to discharge. I'm pretty sure this was a change since Campaign 196 because it used to charge for the first 30 minutes of the first drive of the day. The normal charging voltage is 14.65 V, yet it dithers around 13.5.
This plot is against time with a 15 minute moving average in black. You can see a point where I stopped for about 4 minutes and despite the car being "off", because I was still drawing OBD data it pulled down the aux battery quite a bit.
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