I have a 2013 Leaf (75 mile range), the 2015+ models are advertised with a 107 mile range. So, I'd like to find out if it is possible to do a battery upgrade, expensive I'd imagine, but is it possible? Also, if my current battery dies within the warranty period, would I get the new longer range battery as a replacement? If not, could I pay an upgrade charge to get the new battery?