jaapv wrote:
In general Li-Ion batteries should be stored at about 50% charge. I don't know the self-discharge rate of the Mitsubishi ones, but for four months I would charge them three-quarters full, disable WiFi and disconnect the 12 V battery and hope for the best.
I would certainly not leave the car connected to the charger which would keep the battery at 100% (at least at Mitsubishi's implementation of "full").
Li-Ion self discharge is almost zero
I have old Lithium battery that I stored for years and I can't notice any significant reduce in voltage
Personally ... I would store my PHEV with 10/15km range left .. so with the EV indicator below the 50% charge .. that is around 66% real SOC.
About the 12v battery ... I would keep a trickle charge connected ... there is no issue on having the trickle charge connected even if the car try to charge the 12v battery too
I'm using a cheap "BLACK+DECKER BM3B 6V and 12V Automatic Battery Charger / Maintainer " for my BMW, and I don't even have to disconnect it when I start my BMW for wake up the engine in the long winter break
I took the cheapest charger which start to work (charge) automatically even after a power cut (this can be useful in case of a power black out which my reset more advanced charger unit) .. since actually this charger is connected to a timer that cut the power 2 times a day for take advantage of cheap electricity .. not a big saving, but this plug ins in parallel to the PHEV 10A charger box