jlangham wrote:I just got my 12v battery replaced at the dealer and wanted them to check my main battery because my Battery Kappa is always in the 12 to 13 range - even though my range on the GOM often says 70ish. The dealer checked my main battery and told me that it was at 92%!!!
Did your dealer charge you for the Li-ion battery pack capacity test?
Batt. Kapa. max is just a calculated capacity value that varies with conditions. The only way to truly test the capacity would be to completely discharge/charge the pack and charge/discharge it under controlled conditions. BMW hasn't publicized the conditions under which the nominal usable capacity for a new battery pack was determined. It was almost certainly done at an optimum temperature and at a pretty low current, maybe lower than the pack experiences in normal driving. The capacity increases as the charge/discharge current decreases.
Apparently, BMW dealers can determine a capacity by slowly discharging and charging a battery pack (I've read over a couple of days). This capacity is almost certainly different from the Batt. Kapa. max value.
jlangham wrote:I think the dealers have all been told NOT to replace the batteries under warranty.
BMW has boasted about the modular design of the i3 battery pack which allows the replacement of a single module rather than the entire pack. I would not be surprised if BMW replaces just enough modules to increase the pack capacity to just over 70%. I don't believe that the pack warranty requires a complete pack replacement or even a replacement of modules containing new cells. Honda was using refurbished battery packs (i.e., packs whose modules contained used cells) as warranty replacement packs for our former Honda Insight.
jlangham wrote:So are we saying that the car has a Battery Kappa number that means absolutely nothing? If that's so, why is it even there? Why monitor it? Why display it?
Who knows? This is a hidden, undocumented menu not intended for i3 drivers to monitor.
jlangham wrote:I know some of you will just say it's used in the overall calculation and that other numbers/factors are there to determine what the "real" life of the battery is. I just find that kind of convenient to not have us know and ONLY the dealer. Of course, they will always say that "it's good!"
It is true that there is no instantaneous way to measure a capacity of any battery pack (many different capacities exist depending on conditions). So it would be difficult to provide an i3 driver with a definitive pack capacity.