Prius will be idle for a month

If the car is parked outside a solar charger panel will prevent the battery discharging.

If inside a battery tender/charger left on would do the same trick. If you have SKS system turn it off.

It is difficult to estimate how often if at all you need to charge the Prius battery as it depends on how much running you do on a day by day basis, but charging over night once a month is probably a good thing.

 

There is a lot of "information" about what you should, or should not, do with respect to not running the car for days, weeks, months both in the user manual and on the forum. How about some science? Configurations a, b, c, etc draw this much power and the battery has this much capacity when new and with use/time.

 

Realistically there are to many variables to be able to give any meaningful results.

From the variance in production, how long before the battery stood before fitting to the car, how long the battery stood discharging in the car before it was sold, did the dealer charge the battery when the car arrived at the dealership, what was the temperature during these events,what sort of use does the car get "long or short runs, once a week/every day", has the car got SKS, does the owner sit in the car with the radio on, the list goes on.

We can say with reasonable certainty that hot weather can dry out a battery and cold weather reduce it's apparent capacity and letting a battery sit in even a slightly discharged state will damage it. The length of time for this damage to occur will vary with temperature and humidity as will the amount of damage.

John (Britprius)

 

Yep. It's quite likely the 12 volt will be flat if you leave it for a month.

Make sure it's not one that plugs into the cigarette lighters. At least on my Gen 2 (believe it's the same for Gen 3), they're not "hot" when the power's off, so plugging in a solar battery maintainer there would be useless.

2010 II 12 Volt Battery Dead After 17 Days of Parking | PriusChat has a TSB for what Toyota suggests.

 

I have gone almost a month with my Gen II with no problems. I just turned off the SKS.
Personally, I would only be concerned if I was going say six months with no activity.

 

Well, why don't you run some measurements and calculations and report back to us, Mr Scientist.

 

How do you turn of the Smart Key System?

Is that really the major source of the power drain or is it whatever computer is always running that uses the most power?

 

It's the button on the left under the steering column on Gen 2 Priuses. Sadly, it was removed on the Gen 3.

Prius Storage Time Limitation | PriusChat has TSBs for Gen 2 re: storage.

Supposedly Instructions to disable the SKS without Techstream | PriusChat is how to disable it on Gen 3.

Will park at LAX for 13 days. Dead battery for sure? | PriusChat might prove interesting to some.

 

Since the rule of thumbs for a safe life on a lead acid battery is about 3 years. On my 2004 Prius I got nervous and changed it after 5 years even though it may have lasted longer.

 

One thing to remember is that, unlike a "normal" car you don't need the battery to start the engine just to fire up the computers (the high voltage battery powers M1 to start the ICE). Also once the computers power on and a few checkpoints are passed the 12V battery is essentially connected to the high voltage battery. There is no "alternator" in the Prius as in a "normal" car... the high voltage battery has a feed that's stepped down to 14.7 V to charge the 12 V battery. You can see this with the scanguage as soon as the computers power up when the car us in the 12 V battery voltage jumps to a constant 14.7 V as this is what's being drawn off the high voltage system. Once powered on the 12V system is actually bring mostly powered by the high voltage battery with the 12 V battery there to provide some extra current for peak periods (like say powering all 4 windows when the butt warmers and headlights are on too).

As for the proximity sensors and trying to turn them off in the III this is not necessary. They power down automatically after some time (seems like 5 days +\-) to conserve power. As such there is no "switch" to turn it off. You'll notice after the system powers down the lights won't turn on as you approach the car and the door won't unlock right away when you try to open it. I think it actually powers the system back on upon trying to open the door to check for the sensor which is why the door then unlocks the second time you try.

As for the life of the battery and how long you can leave the car without starting it depends in many factors such as the temp where the car is and age of the battery. I'd say anything up to a month is probably fine for a healthy battery. After 2-3 years its probably a good idea to periodically check the 12V voltage both base and under load to see how healthy it is (this MUST be done with the car off or in accessory mode as once all the systems are on the the high voltage system powers up you'll just read the recharge 14.7 V feed from the high voltage system.

Personally I have a jump pack in the back just as part of my standard kit just in case. Have never needed it with the Prius but has certainly come in handy when jumping other cars (I may or may not have accidentally created a battery drain when fiddling with a different car's audio system once causing the battery to drain after a few days ;-) ). If needed jumping the Prius requires very little current since again you are just powering up the computers not the starter like in a normal car.

 

Not to Worry ... We went to New Zealand last year for six weeks. Left the car in the garage the entire time. Started up fine when we got back. No worries! (2010 Pearl White Model II).

 

Have a good friend take it for a spin once a week.