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Hi. I am going to take a week off from work & going out of town. I like to get information on how to put the 12V Battery in sleep mode, disable or unplug it. (what ever the technical terms you call it)
Reason why when i was out of town for 3 days weekend back then, the battery die on me! I had to called AAA to jumped start on the next day morning before driving to work. it was quite a shock to me when that happened!
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please reponse
thank you for your expert help
Prius_lam (05-2007 / 52.6MPG / 50000K+)

As long as you don't have any interior or exterior lights on, there is no need to do anything to the 12V battery. I have left mine for over a month with no problems. You can also turn off the SKS which will reduce the drain slightly. Also lock the car as it will insure that all doors are closed tightly, thus no interior light is on.

If your battery died after 3 days, either you left a light on or your battery has a problem. Draining this battery does damage it, so you need to have it tested to see if a replacement is needed. A good source (other than your dealer) is: http://www.elearnaid.com/12vo1topraub.html (2004+)

JeffD

Hi, prius_lam (& any new owners who may not be familiar with this proceedure),

As just suggested, turn off your Smart Key System if your car has it. Do you have the little square black buttons on the hatch & the 2 front door handles? If you don't then don't worry about it. If you do, open your driver's door & get down on your knees (so you can get a better view). At the bottom edge of the dash & just to the left of the steer'g column, you should see a little push-button. Look at its position before you touch it. I think it should be stick'g out about a half inch for the system to be on. If I'm right about the distance then push it in & see if it stays in (only stick'g out about 1/8 of an inch now). I'm not sure which position is for "on' & which is for "off" because I only do this once or twice a year. You'll know if you turned it off by trying to power the car up (without the fob in the dash, of course). Or you can close the door & see if you can lock the car by the little square black button. If neither works now, you've turned the Smart Key System off to avoid the small current drain that it uses. Now you have to lock & unlock the car doors & hatch by puhing the buttons on the fob. If your fob battery happens to be weak & not work too well, in a pinch you can always use the little metal key (hidden inside the fob) to unlock or lock the driver's door (it will lock/unlock all the doors, but only has a keyhole for the metal key in the driver's door).

If you don't normally lock your car, then as already suggested, lock it (with your fob) before you leave. If you get one short confirmation beep or chirp from your car & the lights flash, then all the doors are tightly closed so no interior lights will be on. The hatch is the one place that fools us all about being tightly closed. You think it is, but you can't see the light in the cargo area if the window shade style cargo cover is in use. When you try to lock the car if you get one LONG beep & no flash of the lights, then either a door or the hatch is still partially opened or you are still powered up (but you would have probably already noticed the triple beep when you closed the door with the power on). Interior lights that stay on will kill the undersized 12 V battery in only a few short hours.

The one thing firepa63 didn't mention was to turn your headlight switch to the "off" position (in case you normally leave it in the "on" position for "instant-on" use when you start your car). If you normally leave your lights on (even if they go out when you get out of your car), with the manual/stalk switch left in the "on" position, there is a current draw still in the headlight circuit that can kill the 12 V battery if the car isn't used for a long enough period.

This has been a continuing topic for years, but I think people must be leaving something on in their Prius's.

Since we bought our Prius in 2002, we have taken numerous vacations where the car sat unused for several weeks at a time; and we have never had the 12v battery go dead.

My 2004 Prius has 125k miles and the original 12v battery is fine as well. A number of batteries were delivered in a weakened state by dealers who let them fully discharge while in their care.

You can do a quick check of your battery status using the MFD and the Maintenance mode screens:

In ACC mode press and hold the MFD info button while turning the lights on and off three times to go into Maitenance mode
Press the on-screen menu field
Press signals - the battery voltage is shown and should be about 12.4 volts
Press the power button (no brake pedal) to put a current load on the battery - the voltage should stay above 12v
Now put the car into ready mode (press brakes and hit power again) - the battery is now charging at about (or just under) 14v
turn to car off to get out of maintenance mode

JeffD

Just in case you -still- want to disconnect the 12V battery, it can be done, but it's not easy. It's in the rear hatch area, and once you have no power you can't open the rear hatch (electric latch). If you do disconnect it, just disconnect the -ve terminal. You will have to reprogram the radio and the auto-down drivers side window once you reconnect it.

How about just getting a "booster"? They are sold at auto places and even in department stores auto sections. Shouldn't cost more than $30-$40. Use it on the under hood "boost terminal".
Or get yourself a "battery tender", that will keep the 12V battery charged. They cost in the $50 range.
A new battery will cost $150-$250 or so.

Thank you all for your replied / these comments, they are all very useful to me especially from Jeff.
this is D greatest Prius forum!
I really appreciated, thank you again!
Lam

Many thanks to jdenenberg. Slightly more explicit version of his procedure:

- Without brake pedal, press the Power button once to enter ACC mode
- Press and hold the MFD Info button while turning the headlights on and off three times to enter Maintenance mode; release Info button
- Press “Menu” (on screen)
- Press “Display Check”
- Press “Vehicle Signal Check” - the battery voltage is shown and should be about 12.4 to 12.8 Volts (normal for an unloaded battery)
- Press Power button without brake pedal to put a current load on the battery - the voltage should stay above 12.0V (if less than 12.0V the battery is not well, or there is an unusual load somewhere)
- Press brake pedal and press Power button once to enter "Ready" mode - the battery is now charging at about 14V (if less than 13.6V or more than 14.4 there is a problem, possibly with the charging circuit)
- Turn car OFF to leave Maintenance mode