BT, FYI, reportedly Tesla is able to provide an eight year warranty on their batteries ("currently" Panasonic) by limiting discharge to 80% of the total capacity and charging to 80%. I don't think that most ebike systems have "smart" chargers, but Grin (ebikesca) has a charging system that you might be able to set and accomplish this. Personally, battery technology moves rapidly and I won't mind changing in a couple of years.