fotajoye wrote:Shortly after I purchased my car, I read that the expected increase in battery density would be about 10 to 15 percent each year.
I seem to recall Carlos Ghosn being quoted as saying 8%/year. But battery technology improves in fits and starts, so you must consider that an average over many years. Is his prediction correct? We'll have to wait a while for the answer to that question!
fotajoye wrote:I had the idea that if that was going to be the battery growth rate, that would be directly proportional to the future range of the car and that 70 miles on the first generation battery wasn't that hard to deal with.
Actually, I expect the range to increase at a faster rate than the energy density of the batteries. There are three reasons I expect this:
1) There are overhead functions such as climate control that take energy from the battery. Assuming these loads stay the same or get smaller in future models, a growing percentage of the battery capacity will be available as the battery capacity increases. Reductions in these loads will improve range without any battery capacity change.
2) Batteries are not the only area of EV technology that will be improved. Other improvements such as weight reduction and improvements in the efficiency of the electric drivetrain will also be realized.
3) Peukert's effect says that as you draw energy from a battery at a lower rate you will be able to draw more energy from the battery. The same thing occurs if you draw the same amount of power but the battery is larger. However, please note Li-ion batteries like the one in the LEAF have a fairly low Peukert's effect since battery resistance is so low. Also, this really only applies to batteries with the same chemistry and I expect the biggest gains to come from changing battery chemistry. Still, this concept should apply if you have a choice of different battery sizes within a given model year.
I think reasons 1) and 2) apply to the MY2013 LEAF in which there are supposedly no improvements in battery capacity yet there should be an improvement in range.