2020 Prius Prime Long Term Storage

Safest bet with 12 volt would be fully charge it and then disconnect the neg cable. You could completely remove too. Or if you have a secure garage and a decent smart charger, you could leave a charger connected. Still, for that long, I’d side with disconnection.

air up the tires to max sidewall pressure, even slightly higher. Alternatively you could raise the whole car and settle onto safety stands. Just high enough to take almost all the weight off.

change the oil and filter.

Fill the gas tank.

Assuming sheltered garage, leave the car windows slightly cracked.

tuck rags under the wiper arms to get them slightly off the glass.

wash the car, and if you’re energetic wax it too. Pay attention to the corners, wheel wells and underbody.

 

Traction battery not at 100% eg. 50->75%

 

It only trickle charges the 12V while it's actively charging the traction battery. In fact ,the manual warns agains leaving the EVSE plugged into the car for long periods as it will add to the drain on the 12V.

Run the traction battery down to below 50% (the manual says to use up the EV range). For sure don't leave it full. Li-Ion batteries don't self discharge, so it'll be fine at medium to low SC.

Use a trickle charger on the 12v or disconnect the 12v negative.

 

Jerry,
Could you please explain why a long term plug in of the EVSE drains the 12V? Is it because the computer is constantly drawing current from the 12V battery to monitor the plugged in EVSE?

 

Yes, II believe so. The charger in the car and it's ECU is aware that the plug is connected and it monitoring the communication pins with the EVSE. That's not a LOT of energy, but it adds up.

 

Could you put the 12 volt on a smart charger while having the hybrid battery plugged in?

 

Sure! Actually, while the hybrid battery is charging, the 12v gets a trickle charge, but that stops when the hybrid battery is done charging.