That's an idea. So, I could get a battery tender and have it in the house to charge up a 2nd battery. Then, when I go on a trip, hook up that 2nd battery to the Prius battery? Does any 12v car battery work for the 2nd battery? How does it hook together? With jumper cables? Positive to positive, negative to negative?
1) Make sure you use a lead acid battery 12 volt. I went to a lawn and garden store and got myself one of those small tractor battery for around $25 2) You can either use a set of jumper cables or make your own. I went to Radio Shack and got some wires and clips and made my own cables. The wires doesn't have to be very think but should be thick enough to carry 15 amps. This is just to be on the safe side. IF you make your own cable, include a 15 amp fuse. 3) Make sure you MOVE SLOW. Check twice before you move. Yes, you're right. It's positive to positive and negative to negative. AGAIN, MOVE SLOW. If you hook it up wrong, the battery could explode.
Based on your given info only, you will have no problems at all. If it makes you feel better, just fire up the car mid-week for a few minutes (until the gas engine shuts down). Battery minders are only useful for longer extended periods of inactivity, say +3 weeks. Jump Boxes similar to what css28 linked are handy to have, regardless of what or how often you drive. Additionally...for what it is worth, before you leave the Dealership with your new purchase, conditionally require that Service demonstrate exactly how to jump start your vehicle. Best wishes with your new vehicle.
If you were sure that the solar panel maintainer has sufficient smart circuitry, it would seem to be a good choice. If you find it for $7.99 at your local CVS it's probably not going to qualify.
Finally. I thought I was the only one that thinks the advice given to OP was overkill. 2 to 3 weeks is a long period of time. 1 week is nothing to a brand new car with a brand new battery. Even if your battery was 3 years old, then you might have to start it up once every two weeks for 10 minutes. Nothing is guaranteed, especially a stranger's forum post on the Internet but your chances of having a problem for the use you describe is next to nil.
If you fire up the car, what's the best way to tell if the 12v has been sufficiently charged before turning the car off again?
Typically, a healthy 12v lead acid battery should last at least two months without charging. However, since the Prius' smart key system draw small amount of power from the battery, it's not going to last 2 months. Your option is to turn the SKS off if you don't want to drain the battery. For me, I'd rather add a second battery since I already have one. The second battery also comes in handy whenever I'm in a blackout. I'll hook the second battery up to the Prius and use the Prius as my generator to power my lights, TV, and computers.
I don't know. With my second battery, I never need to do that. Look at the manual or google it. With the SKS off, I think you'll need your mechanical key to unlock your car.
The Gen 2 cars had a button you could press to disable the SKS. The Gen 3's don't but will shut it down after several days of inactivity.
I have a similar device that I got at Sears. It's very high-techy and digital. It thrills me to know that I have a device that can jump start my car. I have used it twice (plus once unsuccessfully, user error, not the charger's fault) on my Subaru. Not a lot, but it still thrills me.
This was meant more as a warm and fuzzy for the OP based on stated planned usage. However if you fire it up in park with no accessories on, allow it to run until the combustion engine cycles off and see no yellow triangle with exclamation sign displayed you are golden.
One thing for sure, if your power windows are not moving up or down quickly, your battery is either dying or not being charged enough.
Turn the car off, wait four weeks, and turn the car on again. If it doesn't turn on, you should have left the car on for longer.
Use the mechanical key to lock the car. It deactivates the SKS until you unlock the car with the mechanical key again. I do this whenever I'm using my 1K inverter in a park to cook rice in my rice cooker (takes 20 minutes) and will be away from the car while it's running (or not running, depending on the battery level).
