I'm seriously considering a 2016 SV given the various incentives/rebates. One of my concerns is also long-term storage. The car would be stored in my detached unheated garage in the Seattle area from about October through April, while I am away enjoying my winter in the Valley of the Sun (Phoenix). Quite a snowbird habit I have acquired!
I have searched through the long-term storage threads here, and it seems the consensus is to leave the traction pack at about 50% SOC, then disconnect and/or use an automatic battery tender on the 12V. Sounds reasonable, and coincides with what other manufacturers suggest for their EVs, specifically the GM Volt. It also fits with what I know about Li-Ion batteries doing best when stored at half-charge, preferably in a cool environment, which my Seattle location fits perfectly.
Here is what I found in the 2016 LEAF manual on long-term storage (Page CH-4):
If the vehicle will not be used for an ex- tended period of time, charge the Li-ion battery using the long life mode once every three months. Do not operate the charging timer repeatedly while the charge connector is connected to the vehicle after the Li-ion battery charging is completed. Doing so may discharge the 12-volt battery. For additional information, refer to the long life mode charging method, in the “Charging timer” section of this manual. If the Li-ion battery becomes discharged, charge it immediately.
Given that 80% is probably not quite that in absolute SOC, and that this would keep it simple for the average owner in all climates, I can see why it would be worded this way. If the DC-to-DC comes on every 5 days to charge the 12V, and potentially (not sure on this), the battery warmers to prevent freezing of the pack, a three month top up to 80% almost sounds like reasonable advice in the keep-it-simple approach.
Well, I wrote to Nissan for clarification, and if they had any slightly different advice for a 6-month absence. What I got back was (paraphrased):
1. Charge the vehicle to 100%.
2. Unplug the vehicle.
3. After three months, have a friend/neighbor drive the vehicle around a bit.
4. Go back to Step 1.
The author (from Nissan Vehicle Connected Services) also noted this was the only Nissan-approved recommendation for long-term storage.
This seems to go against the advice in the manual, as well as the annual Battery Information report card which has a line-item for "Long-term Parking with High State of Charge" (implying that condition is not healthy for the battery).
I would think it is best to follow manufacturer recommendations to maintain the warranty. It is disconcerting to see such mixed messages from both the manufacturer and the MNL community.
Personally, I am leaning in the direction of 50% and disconnect the 12V. Another idea I have thought of is leaving the vehicle connected to my OpenEVSE and using the RAPI interface to enable charging once every three months. I'd have to make sure that wouldn't discharge the 12V battery, or use an automatic battery tender to make sure.