My 2013 Leaf 12-volt battery dies every 6 to 12 months or so. The dealer has replaced the 12-volt battery several times, but neither they nor the dealer have been able to figure out what's really wrong. Sounds like others have had the same problem. So I'm offering my simple solution to get up and running reliably (for the next 6 months at least).Updated Nov 21, 2017
1. If the 12-volt battery voltage is very low, but not totally dead (i.e. you can power on the car, but there's error messages on the dash), reboot the car by disconnecting and reconnecting the 12-volt battery. If you don't reboot, the built-in 12v recharger/maintainer will not turn on and the 12-volt battery will die again within a few minutes.
2. Jump start the car.
3. After disconnecting the jumper cables, leave the car on in ready-to-drive mode (not in accessory-only mode) all day or over night
. For safety's sake, I make sure the emergency brake is on and my garage is locked.
As long as the car is in ready-to-drive mode, it is recharging/maintaining the 12-volt battery. The owners manual says to leave the car in ready-to-drive mode for 20 minutes after a jump start, but that's not enough, and it will die again very soon, so don't take it out on the road.
I've been through this cycle many times, and to my surprise when the dealer tests my 12-volt battery, they say it's in good condition.
Another option to simply get more 12-volt recharging/maintaining time is to use your old level-1 120v charger to charge your drive battery instead of your 240v level-2 charger for a while.
The key here is to understand that the car's built-in 12v recharger/maintainer is operating only when the drive battery is engaged, i.e. in ready-to-drive mode or with drive-battery charging (actually charging, not just plugged in).
Of course, if anyone is aware of any fix from Nissan for the battery dying in the first place, I'd love to hear about it. After going back to the dealer with this problem so many times (and even leaving the car with them for a whole month once) with no solution, Nissan is suggesting I use their buy-back program. With 55k miles on the car after 3 years, I don't expect a very good offer, but we'll see. Hoping for the best.Updated Nov 21, 2017
Nissan declined to buy back the car, but did give me an extended warranty instead with an additional 4yrs/48k miles (and that's already saved me around $1,000 on 3 wheel bearing replacements).
I recommend purchasing this cheap and convenient way to keep an eye on the 12v battery during the process above and to learn how it's maintained.https://www.walmart.com/ip/Equus-Innova-3721-Battery-and-Charging-System-Monitor/15137663?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227009075049&wl0=&wl1=g&wl2=c&wl3=40839218672&wl4=pla-78652684352&wl5=9009731&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=15137663&wl13=&veh=sem
When in accessory mode, you'll see around 11-12v - any less and you're having trouble. When in drive mode or when charging the drive battery, you'll see either 13v or 14v - a few minutes at 14v then drops to 13v. Ignore the red, yellow, green lights which seem to be calibrated for a gas car.
2013 Leaf SV - Built 03/13 - Pearl White - QC Port - LED Headlights - Bosch PowerMax 240LC EVSE - New drive battery for $500 (mostly covered by Nissan) at 75k miles!