Ran across this great presentation from Professor Jeff Dahn (Dalhousie University) talking about various issues in engineering batteries for EVs (and other applications) that last a long time. Professor Dahn has been working with GM for a year or two now helping them in their battery testing lab.
[youtube]http://www.youtube.com/watch?v=pxP0Cu00sZs[/youtube]
Notes:
[youtube]http://www.youtube.com/watch?v=pxP0Cu00sZs[/youtube]
Notes:
- Coulombic efficiency is an easy way to compare cycle/calendar life of a lithium batteries without having to run very prolonged cycling tests - the better the efficiency, the more durable the battery.
- Chemistry (and additives) are vital in determining cycle/calendar life of a lithium battery.
- The colder the battery, the longer it will last (Arrhenius' equation).
- The lower the SOC the battery is charged, the longer it will last (example was storing battery at ~20% or 3.5V resting voltage).
- LiMn (as used in the LEAF/Volt) has horrendous cycle/calendar life at temperatures of 30C+ compared to say LiCo (as used by Tesla). LiCo is even better than LiFe (A123).
- Additives can have a very strong effect on coulombic efficiency (and thus durability)