I'm way late to this discussion, but I started at page 1 and read thru page 12 - and the result is a spinning head (that would be mine). If there's anything definitive about whether to get a new battery, it didn't sink in, but really I think it's because every situation is unique - by year, climate, use, maintenance, etc. My wife loves her 2012 SL, and we really can't afford a new one (though we'd think about it if Nissan ever matches what the Bolt and Model 3 can do). I'm no expert in figuring out this car - navigation confuses me, and my wife can't even find the driver's controls for windows and locks so she just reaches over to lower the passenger window. I think it's maybe because we're kinda old. But I do know we're down a bar in 5 years and 17,000 miles. The car spent all of its life in Los Angeles, always parked on the street in all kinds of weather (well really there's only two kinds of weather in LA, warm and hot - anything else is an anomaly). I've read all kinds of stuff about the effect of heat, even if the car isn't even being driven. Been using a 240v charger conversion for 4 years. Read all kinds of stuff about how/when to charge the battery - let it drop to 20 miles (we always looked at potential miles, not percentage charge), or charge it when you need to, or don't charge it when you still have half or more of the charge/miles left, or whatever. She would get range anxiety, mainly because she had to drive home late at night through The Street of L.A. with lights on and stop-and-go-and-stop-and-go block by block, a long gradual uphill until near the house when the climb became steep, and she did NOT want to run out of juice. So she'd get home with 40 miles or so remaining, and charge it up. She averaged 3.5kw/mile over all those years. About a year ago we noticed we'd lost a bar of charge, and instead of predicting a 90-100 mile range as when new, it was now 80 max and mostly mid-upper 70s. That seems like a greater proportionate loss of miles than it does of charge, which is confusing.
OK - a week ago we moved to Eugene Oregon (Subaru country). Still no garage but at least we've got a carport. It's been in the 40-60-degree range since we got here and it's only going to get colder (though the cold here can't compare to cold in the Midwest, for example). I don't know if 40-degree temps qualify as cold when it comes to battery power, but we do have to have the heat and defroster on a lot. It still shows one bar down, but suddenly the miles forecast is only 60 max. Well, Eugene is small, every place is close, it has timed lights on one-way streets - a traffic paradise. We're just concerned that we're going to lose more and miles per full charge, it worries my wife, and so we're looking into a new battery - more affordable than a new car, and really there is nothing wrong with this truly solid car (17k miles in 5 years) other than the loss of battery capacity.
So - what's your best guess for what we should do? We're past the 5-year warranty (if that's the one that matters in batteries). We'd spring for a new one even if we had to pay for the whole thing. It seems really hit-or-miss and who you talk to at Nissan as to whether they'll pay any of the cost. And it's only 1 bar - yet what's confounding for us is that we've lost almost 40% of our range. I've read that the early Leafs can't take the 30kwh battery, but a new 24 would be great. And we'd sure appreciate some sound advice on when/how to charge it to maintain its capacity as long as possible.
And thanks to everybody for maintaining this really great forum. One of the best things about the Internet - it widens your circle of acquaintances exponentially.