mogur said:
I still contend that charging to 100 percent is less stressful for the battery than discharging to 10 percent or less... This is true for almost every lithium battery ever made and I have a hard time believing that the Leaf battery would be any different.
In general, if you're talking about a raw cell, and that cell is LiFePO4, then I'll agree. If the cell is LiCo/LiPo, then I will not agree.
Because LiMn2O4 is closer to LiCo in the family tree - and industry tests conducted on LiCo clearly show that max charge voltage has a very, very significant effect on cycle life.
http://batteryuniversity.com/learn/article/explaining_lithium_ion_chemistries
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
We keep coming back to this point, though. Yes - if one has a RAW CELL they can choose to over charge and/or over discharge the cell. The info in places like battery manufacturer spec sheets is for raw cells -
cells not protected by any type of management system - because the intent of those authors is to describe the cell. Places like Battery University tend to mix/match info for raw cells and complete batteries with management devices.
But we are not allowed to access either end of the Leaf's pack - NISSAN has Protected the Pack from US!
As consumers, we are free to use only the capacity Nissan allows us to use.
A good low voltage cut-off point for LiCo/LiPo/LiMn2O4 if we expect a long life is 3.0V. This is what I use when building management systems for LiPo and LiMn2O4 batteries. The Leaf's battery management system will only let us come down to 3.2V-3.4V as an absolute minimum - this sets an over discharge error code that results in a 'no charge/no drive' condition. Minimum cell voltage for a 'ready' condition is between 3.3V and 3.5V. (Service manual, section EVB, P.28, P.93 and P.103)
Bottom line - the car will not let us get into low voltage danger - or into a voltage range that would shorten the cycle life of the pack.