GaleHawkins said:
You followed my testing procedure and was able freeze your SOH I Iake it.
I think Sagebrush's point was that the SOH value came only from the BMS, and that the margin of error on that value is high enough that you really can't conclude that you've halted SOH degradation by simply disconnecting the 12v battery for a fully disconnected "shelf-storage".
As a data point, while waiting for the 4th bar to drop (mine did it at 65.84% SOH, while others dropped a little earlier than this), I noticed that the SOH value went UP a day later (probably due to weather change?) by about 0.08%. With that kind of error rate, you're going to need to have a ton more data before you can be sure that the degradation had actually dropped.
As a shade-tree electrician (computer engineer by training), I can see the logic that disconnecting the main pack from the 12v battery would remove a parasitic load from the main pack (and thus reduce the charge cycling). But that thinking is incomplete. Even though you've removed the electrical load, the thermal load on the liquid electrolyte is still present, which is why calendar degradation is a thing. You're in KY, so your weather is better for maintaining battery health, but it would NOT work in warmer climates like the southwestern states.
As for the Prius C, it's a non-plug-in hybrid, why forgo putting miles on the Leaf just to preserve its battery for 10 years?
Edit: @ RandalC, mine dropped the 4th bar at 65.84%, I've seen others dropped within 1% of that value. So 66.8% - 64.8%.