pbui19 wrote:By "calibration charge", I meant to charge from the blinking 1-2 bars to 100%. My understanding is that when the guessometer hits 2 and below bars, the BMS goes into some sort of integration mode to reset the available Ah. In fact, I don't understand how does the software calculates and reports the pack Ah without a calibration charge.
Yes, only a near full discharge from full or charge to full from nearly discharged gives the BMS the opportunity to measure the Ah capacity properly.
In between those few times when it can measure it it simply follows a programmed in "assumed degradation" model. If you have a look at my Ah graph
You can see the shallow gradient of about 0.1Ah per 1000 miles is the programmed in degradation model. Periodically the larger drops are based on actual measurements so it can be seen that for my car the actual degradation over the full time I've owned the car is at a much greater rate than assumed by the model in the BMS...about a 3x steeper drop. (in other words Mitsi underestimated the battery degradation)
I would say in general, the pack capacity is the input Ah between the SOC when ONE cell reaches the bottom, 2.9 v ?, and ONE exceed the top at 4.10xx ? essential in between the high/low knee voltage curve.
Yes, although fully discharged (0% SoC reported in Canion and the car shutting down) is 3.63 volts per cell on my car. There is some evidence that as the batteries degrade and lose capacity, a little bit of capacity at the bottom end is "unlocked" by allowing the cells to discharge lower than 3.63 volts. But not too much lower.
Both Canion & Hobdrive are reported my pack at 36.9 Ah at 22Kmiles; but I can't honestly tell whether my range has diminished. It's the range that matters, not the reported Ah.
Mine was at 39.9Ah at 28k miles which at the time was good and seemed better than most other Ion's however after a series of large drops in reported capacity I'd say that mine is now significantly worse than most. I definitely have at least 2 weak cells that are probably responsible for most of the drop and have toyed with the idea of replacing them, however sourcing known-good second hand cells at an affordable price, and having the where with all to replace them (requiring a full day with access to a 2 post hoist) is not easy, so I'm not sure whether it's worth the trouble.
I've definitely lost range on mine - summer range has gone down from about 63 miles to 55 miles in the 2 years I've had the car, and who knows what the next 2 years have in store for me. As I can barely make my daily commute in the winter as it is now, the next two winters will be tough. I have a rapid charger to fall back on but that adds significant time and cost to the journey home.