If there really IS any
If there really IS any unusual 'capacity' loss in these vehicles, as their owners believe, the ONLY way to know for sure is to remove a suspect battery pack and bench test it by fully charging it, then discharging it through a known load while periodically measuring the power dissipated, the sum being the capacity in kWhrs - that's what a professional grade watt-hour meter does, in essence. This is the MOST accurate way to measure battery capacity. I know this because I am an electrical engineer. So far no one has done this, have they? No, what both Nissan and the testers are relying on is data coming from the vehicles in question, which could be faulty. The range test fails because if the Leaf detects faulty data it will go into 'turtle mode' prematurely - the driver will never know that there COULD be significant unused capacity. Recently, some Leaf owners experienced charger failure with the GE WattStation - the fault turned out to be in the Leaf on-board charger which failed when there was a brown-out condition during a charging cycle (a power surge could possibly cause the same issue). I suppose Phoenix and other hot area probably experience brown-outs, so these Leaf's in question may have had a failure of some component in the charging or sensing circuitry. Such a failure could result in a misreading of battery terminal voltage level (which as I understand it the Leaf uses along with a Hall-effect current measurement, despite inherent inaccuracies, for capacity calculations) which in turn could result in the loss of bars reported, or even, worst case, an overcharging of the battery pack and resulting damaged cells. There is an old expression - garbage in garbage out - so relying on the Leaf's data output derived from sensed terminal voltage, when the sensors could be at fault, is NOT definitive. Heat affects all sorts of electrical components - copper wire resistance goes up with temperature for example. Undetected errors could also be present in the firmware - perhaps if the calculations use a temperature measurement, then the hot climates could cause some glitch to appear in the calculations. I think the folks in AZ have jumped to the conclusion that it has to be heat damage to the battery pack, perhaps spurred on by comments by certain Nissan competitors? Rigorous controlled testing of the Leaf's in question down to the circuit level should be performed before any conclusion is reached. As a fellow-Leaf owner, I look forward to that. In the meantime, Nissan should settle with the few disgruntled Leaf owners out there.