It seems more likely that the marginal batteries in the 2013 just made obvious an underlying problem that is usually brought to light only when the car is left plugged in for longer periods, or driven on lots of short trips. I'm fairly sure I've read posts from drivers of gen 1 leafs with the same issue. Also, I had the issue with mine over a year ago, and the battery has been fine ever since with the maintainer in use. Bad batteries don't usually last that long after being drained even once.