My 2004 will be parked for 3 months while I'm away. Is there anything I should do to protect and or prepare the hybrid battery for 3 months of non-use? Toyota's website says: "For the hybrid vehicle battery, charge the battery at least once every two months by starting the hybrid system for about 30 minutes." But, I won't be able to do that, since I'll be gone for 3 months. Ideas?
I have seen the battery gurus here say that the Hybrid Battery can go longer than three months with no problem. If it is reasonably full at the start, it would have to be in very poor shape not to start the engine. I would be more concerned about the 12V battery. A trickle charger would be needed. Also, push in the SKS key under the steering wheel, if you have that. Having someone turn the vehicle on and running it occasionally would be best.
I would make sure the hybrid battery state-of-charge shows six bars or better before storage. You can force-charge the traction battery by making the Prius READY, shifting to D, pressing hard on the brake pedal with your left foot to hold the Prius stationary, then flooring the acccelerator pedal with your right foot to rev up the engine. The engine power is directed to MG1 since the car is motionless, which will provide power to the inverter to quickly charge the traction battery. After the traction battery SOC is adequate, then I suggest you turn off the car, close all windows, then disconnect the 12V battery. You can either disconnect the battery at the main relay/fuse box by removing the nut at the dedicated positive jumpstart terminal and removing the attached cable; or you can disconnect the negative battery cable where it connects to the body. The former is easier as it will be hard to open the hatch without battery power connected. For a complete job, you should fully charge the 12V battery, using a battery charger. I also suggest you check tire pressure and inflate at least to spec; or higher if your practice is to observe 44/42 psi, for example. That will reduce the likelihood of flat spots developing. Even better is to raise up the car with four jackstands.
