10-month storage

There is a product for maintaining batteries in storage.
12 Volt-1 Amp Charger and Maintainer

JeffD

 

This corresponds exactly to Toyota's advice regarding long-term Prius storage.

 

Worst case, dont buy a new Prius when you return, just buy a new battery. If your battery is five years old, it is approaching the end of its life anyway. However it would seem the absolute peak price for a used Prius is right now today, which may not be so true in ten months.

But best case, just buy one of these battery chargers and leave it connected while gone:
http://www.amazon.com/dp/product/B0009IBJAS?tag=priuschatcom-20 have the Schumacher, and it's great.

These are low power battery chargers (more specifically, a "maintainer"), which are expressly designed to be used during long storage to keep the battery fully charged. These are very small chargers, which may take a full day to recharge a low battery, but is designed then to easily and safely keep the battery fully charged in storage. Basically the same effect on the battery as leaving the car in Ready 100% of the time, which is a very good thing to do for the battery. Keeping the lead-acid battery fully charged is the best possible thing you can do for it to insure its long life. This prevents the sulfurization which always occurs in a low battery, which ruins the battery.

These just clip on in the fuse box under the hood. Be very careful to observe correct polarity, red to red, and black to ground. However for 10 months, I would disconnect the battery from the car, and connect the charger to the battery.

Be sure to turn off the Smart Key button under the steering wheel, to prevent the continual battery drain that it causes.

 

You might also what to consider a fuel stabilizer like STA-BIL.