If you've had issues with the 12V battery in your leaf failing prematurely, go out and unplug the low voltage connector on the negative terminal.

[NoahJ]

Going to try this as well after having disconnected the cellular system which I believe was also killing the battery. Thanks for the suggestion.

Edit: that was weird. I was reading the post about disconnecting the negative terminal and posted to reply there and it ended up here….

 

[Pepperoni]

Thank you so much for digging into this! I am currently going through the dead 12v movie with my '22 Leaf that has 12,000 miles. I managed to recharge the battery and get the car to Jim Bone Nissan 60 miles away, four hours later they told me the battery was fine but offered to sell me a new one for $250. We made it home but the 12v battery was dead the next morning. Because I bought the car used, I do not qualify for Nissan Roadside Assistance and my insurance only covers a 10 mile tow before the $8 a mile charges kick in. Plus the idea of paying $500 to tow a car to someone that cannot diagnose a bad battery seemed silly. I've ordered an Interstate AGM and put a piece of double sided tape between the connections of my temp monitor to maintain the stock appearance, hopefully this will put my battery problems behind me.

 

[mcmancuso]

Just for the sake of A-B testing, I plugged the connector back in, and the car was right back to dead battery within a couple weeks. Connector off and it's staying charged. IDK if the fault is the sensor or the programming of the ECU or what, but clearly there's something very wrong with how the ECU interacts with the 12V battery and this sensor.

 

[cornbinder89]

Those that are have the shortest life, most dead batteries, I have a question. What trim model do you have? The higher trim models came with a solar cell on the rear spoiler. Nissan must have recognized a drain problem and added the cell to address it. There is really no other reason to do so.
So far I have not noticed a problem. I have mentioned before that I have three vehicles with these Gr 51 batteries, all charged by different charging systems.
I am hoping to get a used current sensor I can modify and play around with to see what can be changed on the Leaf system.

 

[cornbinder89]

Nissan service manual say "dark draw" on the battery should be less than 50 ma. or 0.050 amps when the car is off, and in "sleep mode".
Has anyone with premature battery failure accurately tested the current draw? That is a fairly small current and most automotive clamp on inductive battery testers would not pick that up. I know mine will not read something that low, I would use a series meter for accuracy at those levels.

 

[mcmancuso]

Those that are have the shortest life, most dead batteries, I have a question. What trim model do you have? The higher trim models came with a solar cell on the rear spoiler. Nissan must have recognized a drain problem and added the cell to address it. There is really no other reason to do so.
So far I have not noticed a problem. I have mentioned before that I have three vehicles with these Gr 51 batteries, all charged by different charging systems.
I am hoping to get a used current sensor I can modify and play around with to see what can be changed on the Leaf system.

They dropped the 12v solar cell with the gen2 (2018 and newer) I have an SV Plus.

 

[cornbinder89]

They dropped the 12v solar cell with the gen2 (2018 and newer) I have an SV Plus.

Thanks for the info, would still like to hear from those with problems, and how their cars are equipped. I'm trying to dig into why some have problems and some do not.
A solar cell diode that failed shorted can increase the "dark current draw" 3x the amount the manual says is acceptable, and will not throw a code. Failed open will just make it in-op. All this according to the manual.