LeftieBiker wrote:The plates get sulfation that won't go away again under normal circumstances.
The term "sulfation" normally refers to lead sulfate which has hardened (crystallized) after sitting for some time in the battery. The shortest period I have read about for lead sulfate to harden is three days (in very hot weather). Otherwise, lead sulfate is in the form of a paste and it is the normal product whenever a lead-acid battery discharges. In that form it readily dissolves and participates in the charging reaction. As such, I have difficulty seeing how a single overnight discharge could result in the hardening of any lead sulfate. That said, it is important to perform a FULL, SLOW recharge following such an event to ensure that none of the lead sulfate remains after the event. As you have said, the LEAF is certainly not up to that task!
That said, I can think of a few reasons why a battery might be damaged by such an event:
1) The battery might be damaged by jump-starting the battery, which subjects the battery to extremely high currents. Such high currents can be hard on the battery and can lead to things such as "flaking" of the lead paste from the plates, resulting in a permanent loss of capacity.
2) By fully discharging the battery, much of the lead on the plates is removed. During recharge, the lead is not replaced in the same manner as it previously existed, which can affect the battery's resistance and perhaps even reduce capacity a bit.
3) Some cells in the battery which had less charge or capacity before the incident may be forced into a reverse-voltage situation during the deep discharge, which could result in permanent damage to the battery.
My E350 van has an annoying problem with the interior lights: they don't have strong detents to hold them in place. As a result, they can be turned on simply by vibration caused by the vehicle being buffeted by the wind. The result is a frequently-dead battery. This problem has occurred on many occasions (perhaps 20). When it does, I use my 1.5A trickle charger to recharge the battery and after all those discharges it still takes the full 36-hour+ time I expect for a full charge. (If the voltage is below about 4V, the charger will not recharge the battery, so I trick it by putting a couple of D-cell batteries in series with the 12-V battery so that the charger sees enough voltage to begin its charge. Once the battery itself is above about six volts, I remove the D-cells. This allows me to fully recharge the battery without ever subjecting it to more than 1.5A of current.)