JoeS wrote:DBMandrake, thank you for posting those images and analyses, and thanks for stress-testing your battery in the interest of science. My impression is that your battery is just fine and does not exhibit the dramatic individual cell failure which some of us have experienced (and which was cause for battery replacement by Mitsubishi).
I think you're right - at least at this point there is no obvious individual cell failure. I guess I just have to come to terms with the likelihood that the battery has been 36.1Ah for some time, perhaps even since before I bought the car but the BMS has been providing a "predicted" figure with a predicted linear degradation providing figures which were considerably higher than the "true" state of the battery, which was not revealed until a full calibration was run. Perhaps this diagnostic tool calibration should be run once a year to ensure the true state of the battery is known and that we're not buying into the BMS's delusion...
I won't know for sure until summer but I suspect that my full charge no heater range will be fairly similar to last summer. Fingers crossed.
Incidentally the "GOM" (Guess-O-Meter) expression common on the Leaf forum does not apply to our i-MiEV: our RR (Range Remaining) is very predictable and is a simple algorithm which is a moving average of the car's consumption in the preceding 15 miles (24km). Even though the RR is offset by, for example, 20% whenever the heater is turned on, as best we can tell this does not factor into the RR past consumption equation. It is predictable because we know the type of terrain, wind, and type of driving we had experienced and can mentally compensate for any changes in these conditions.
If only it were that simple...
Yes, the consumption caused by the heater and AC is added on "afterwards" and does not factor into the miles/kWh average that it uses to calculate the base figure (at least as far as I can tell) and yes, while driving it does appear to average your miles/kWh consumption over approximately 15 miles. (Although it seems less than that to me, more like 5 miles)
However.... there is something special about the RR reported after completing a 100% charge that is definitely not just the average of the last 15 miles completed before charging.
Because I often get wildly varying RR on full charge from the exact same work commute with about the same actual consumption. (Judged by the number of bars left when getting home being the same)
At the moment I am seeing a full charge RR of only 53 miles, two full days after driving the car fast, and yet over the first 8 miles of driving the figure actually goes up from 54 to 56, indicating the true figure of distance driven plus range remaining is about 62 miles, which would be about right.
And despite maintaining an average consumption to give 62 miles per charge, the next day I will get an underestimated RR at full charge of 52, which will again go up as I drive.
Conversely I often see a RR on full charge of between 75 and 84 (!) miles despite following the exact same driving pattern, in this case the RR drops rapidly over the first 5-10 miles of driving.
So in my experience the RR figure after completing a full charge is highly unstable and untrustworthy, with figures anywhere from about 50 miles to 84 miles with pretty much identical driving. Only after I have done about 10 miles will I start to trust the RR figure and by the time the battery is down to below 50% it is very accurate.
What's going on to cause this ? I'm not sure. But one thing I'm certain about is it's not just using the average of the last 15 miles driving before charging. It's simply not possible for it to give these kind of figures with my regular commute. I'm still trying to find a correlation to explain where it gets its bizarre full charge RR figures from.
The last thing to stress is that whenever we talk about energy consumption we must distinguish between wall-to-wheels (which some of us had laboriously calculated) and battery-to-wheels which many cars show on their dashboard and we have see on CaniOn. My personal figure-of-merit (efficiency target) for the i-MiEV is 100Wh/km as shown on CaniOn, but I use the wall-to-wheels number of 4.2mi/KWh (meticulously measured over 8000miles) for any calculations.
Yep, I'm well aware of the difference between wall to wheel and battery to wheel.
Prior to getting Canion all my readings were wall to wheel, and that is what matters for working out charging costs and times.
However battery to wheel is what counts for working out driveable range from battery capacity, hence using those figures for the recent calculations.
However to get from 5.3 miles/kWh battery to wheel to 4.2 miles/kWh wall to wheel would imply a charging efficiency of only 80%, which seems a bit on the low side to me. I have a DIN kWh meter in my charge point so I could do a direct comparison between I charge at the wall to the reported figure on Canion to estimate the charging efficiency.
However I think Canion's estimation of current and power at very low powers (like when stationary) is significantly out.
For example it tells me that there is 0.3kW being used from the traction battery when the key is turned on but the car is not in READY mode - which is completely impossible as the contactors are open in this state isolating the battery from the rest of the car! So something is not right with the low power measurements provided by Canion.