Magiclamp wrote: ↑
Mon Sep 14, 2020 10:55 pm
Based on ur formula, i am only getting 12.5 kap. Did it 2x and both time getting the same result.
You may want to try a few more times to get an idea how consistent the result is. My experience is that any metric used to calculate battery state of health has some variation in it that makes it hard to point to a definitive number.
The other piece to consider is that unless you ran the battery until the car literally stopped (I'm not advising doing so), there was charge left. You could divide your value by (100 - the % remaining) to factor in any leftover charge. However, my experience also suggests that the i3 does not display discharging as linear so this value may be skewed.
Here are all the ways I have found to measure state of health. I have been tracking all of these for a while on my car and have seen each one bounce +/- multiple kWh between readings in some cases with little rhyme or reason. These numbers are all from the same reading. Even here, the range between them is 1.4kWh:
1) Batt. kapa. max from the hidden menu
2) Batt. Ladung kWh from the hidden menu / State of Charge.
(eg. Batt. Ladung kWh of 1.8 / SOC of 15% is 12.0
kWh total capacity)
3) (Trip Miles / computer's consumption rate (mi/kWh) for the trip) / (100% - State of Charge)
(eg. (54.7 trip miles / 4.8 mi/kWh) / (100% - 15%) = 13.4
4) (Trip Miles / computer's consumption rate(mi/kWh) for the trip) + Batt. Ladung Wh
(eg. (54.7 trip miles / 4.8 mi/kWh) + 1.8 kWh = 13.2
5) If you have the Electrified app and a OBDII dongle, you can get the SOH reading from there. Mine claims 69%.
6?) Folks have said BMW's test runs the battery flat and measures the amount of energy it takes to recharge the battery to 100%. My Juicebox smart EVSE measures the energy it passes to the car, however without knowing the exact efficiency for any given charge (did the car use the AC/heat for battery conditioning? etc.) I haven't found a way to use this as an accurate estimate.
If all of these consistently
point to a number below 70%, I think you have a good case to go to a dealer and ask for a test (and argue that it should be free), however since BMW claims the car will notify you if the battery has lost enough capacity to trigger a warranty claim you might want to be prepared to have to pay for the test no matter what your data says.
Having said all that, I am paying attention to these threads as well for evidence of battery replacement/ what BMW is actually using to determine the threshold.