As I understand it, calendar life is a factor with most lithium. (I don't know how much this applies to LiFePO4.) Getting 48000 miles in 3.5 years is probably good service; but coincidentally, 3.5 years is just about where you often begin to see calendar life degradation start in other products. (Think about laptop computers, mobile phones, and so forth.)
I'm no expert on this, but I think I recall reading that one of Tesla's distinctive approaches to battery design was including a way for the battery to sort of "patch around" failing or failed cells. The principle is different, but it makes me think of Lee Hart using his battery balancer to keep weakening modules powering his EV. In each case, you're accepting the fact that some parts of the battery last longer than others, and working around that. Just as Lee's battery eventually got to the point where he could no longer keep it propped up, I suppose there's a limit to how many cells a Tesla can delete from the battery without excessive capacity loss. (Assuming I'm remembering and understanding all this correctly.) All that said, cycle life is heavily dependent on treatment, and those 3- year-battery-life consumer electronic gadgets are notorious for being careless. BMS configuration, temperature regulation, current use, and routine DOD can make a huge difference, to say nothing of cell quality. For example, over the years, I've owned several Thinkpad laptops. The 760EL ran for over 10 years on its original lithium battery; it capacity gradually and gracefully declined, rather than falling off a cliff. OTOH, I couldn't get a battery to last even 3 years in the 600E. David Roden EVDL Administrator http://www.evdl.org/ _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
