Storing charged Li Ion batteries varies on chemistry, but they typically have a self discharge rate of 8%-15%, depending on temperature. Discharge usually tapers off in these batteries, as cobalts are good to store around 40-60%... as the loss is 2-4%.
80% sounds like a lithium ion polymer storage charge, no idea what the recommendations are specifically for the leaf's chemistry.
Honestly, while discharge rate is interesting, I think it is mostly irrelevant unless the car is going to be sitting for extremely long periods of time. If you are talking about six months, id be concerned, but even a month is probably going to not be much of a bother.
You are going to charge it anyway...its not like its an emergency locator beacon where you need a good chunk of the power available on a moment's notice 5 years from now!
The key to good battery life is frequent usage/exercising of the battery.
Anyone in the armed forces should probably take special care -- i had a friend park a car for years. It was almost comical that he had a 4 year old car with only a few miles on it and brand new! It was a hybrid too .. wonder how the battery pack did (NiMH are especially nasty when left to waste)
Ordered 11/24/2010 (November)
Red SL-e, ECO package, cargo, splashguards
Commute: 75 miles round trip (60 miles highway, 15 side roads)
miles: 45,000 miles
Charge daily to 100%, lost 1st bar at 43k
" onclick="window.open(this.href);return false;