Extended Vacation

Your 12V battery will be dead after 45 days, if you don't take either of two actions:

1. Disconnect the battery, either by removing the negative battery cable where it bolts to the body; or else the positive wire at the dedicated jumpstart terminal in the main relay/fuse box next to the inverter.

2. Hook up a battery tender so that the battery will remain charged up - which requires access to an AC outlet where the car is parked.

 

I would do several things; First, do a force charge on the traction battery. This is very easy, once the car is warmed up, put the car in drive, and with 2 feet, hold the brake HARD with your left foot, and press the accelerator pedal with your right. You can press the accelerator all the way, the Prius will safely limit the charge amps, and as the battery nears full, you will hear the RPM drop. You can also watch the MFD, when you see all bars lit, you can release the accelerator and shut off the car. It should only take a few minutes to get the charge full. Note that this is not strictly needed, especially for only a short trip, but won't hurt.

The other, and most important thing to do, is disconnect the 12V battery. If you don't do this, you will have a dead battery upon return! It will also drastically shorten it's life even after you recharge it.

There is an easy and very safe way to disconnect the 12V battery without tools, and anyone should be able to do it even without experience:

1. Open the rear floor hatch, (under the cargo mat if you have one) remove it, and set it aside.

2. Lift out the big black cargo tray, and also set it aside.

3. Locate the carpeted triangular-shaped plastic piece on the right that fills in the floor of the cargo area. This is the battery access cover.

4. You should be able to carefully unhook it from the surrounding trim by lifting it up and out towards the left. Note: There is a little plastic cover panel that is connected to the rear of this cover that sticks up. Do not try to separate this from the battery cover! It has 2 little hooks that keep it engaged with the rear trim panel. If you are having trouble, be sure to verify the top of this plastic cover panel is free of the surrounding trim.

5. Now you should have full access to the battery area. Unsnap the red plastic battery terminal cover as shown in the picture below. It slides toward the front of the car once the 3 tabs are released. I find it easiest to hook my finger under the red cover on the side farthest from me and pull the red part away from the black part while also pulling toward the front of the car.

6. Locate the large white connector with the thick black wire. (see picture below) This is the positive wire that feeds 12 volts to the car. It's connected into to the black junction box assembly, and there is a release tab located under the white body. Simply pull up on this tab while pulling it toward the front of the car, then the connector should easily unplug from the housing.






If you are storing the car inside, You can then put the car back together, but BE SURE to place something in the rear hatch so it doesn't shut all the way! This is because the hatch will not open with the battery disconnected! If you do not have a garage and will store the car outside, I recommend you leave the seats down and the car apart in the rear so you can crawl back in through the front and reconnect the battery.

Note that you should verify your mechanical key works before locking the car, as it will be needed to gain entry after locking.

When you reconnect the battery, you will have to reset your clock and radio presets (if any), then reset the driver's auto window: Once the car is on, roll the window half way down, stop, then pull it all the way up and hold the switch for 1 full second even after the window stops. Voila!

 

Looks like Patrick beat me to it! =)

The battery tender is probably not needed if your trip is a few months or less as long as it's disconnected. If your trip is going to be longer, in addition to the things I mentioned, also fill the car up with a full tank of fuel before storage and add about 10-15 PSI to the tires. This will help the fuel not degrade and your tires from getting a "flat spot".

 

Nice stuff pEEF. Thank you.

 

Is two weeks pretty safe? We do not have SKS.

Rudy has a new 12V battery, and he will be sitting unused while we are on our cruise. Otherwise, I can arrange for him to be driven a couple of times while we are gone.

 

Just follow my 6 easy steps in the post above to disconnect the battery, no tools needed! It will help it last longer!

 

i have left my 04 and 08 for 45 days every winter in an unheated attached garage for 6 years without doing anything and have had zero issues.

 

You are saying your 04 still has the original 12V battery? I seriously doubt it!

Letting the Prius (even w/o SKS) sit for an extended time will deep-cycle the 12V battery. Even if it still somehow manages to have enough left to start your car, it will take a lot of life out of it, as the life of a lead acid cell is a function of depth of discharge times the period of time it sits at that SOC.

It's also a good idea to top off the traction pack, especially on longer trips. If the traction battery happens to be low when you park it, it could get dangerously low after sitting unused for an extended time. The force charge ensures that it's at least at 70% SOC.

 

to be more specific, i left the 04 every feb and march for the first 4 years. my daughter has had it since then and it doesn't sit more than a week or two at a time. is it the original battery? i've been wondering that myself. we've never replaced it and the only work she has had done was when a deer hit her a few years ago. didn't damage beyond the rear door but they might have replaced it if they saw damage? can't find the paperwork and i took a look at the battery without removing it and couldn't find a date code.

 

Even here in the mild bay area weather, I find that that most all 04's have already needed at least one battery by now. If your battery is over 5 years old I recommend you replace it simply as preventative maintenance unless it's an Optima. I have yet to see an Optima go bad in any car from around here.

My 2008 is on it's last legs, but I've not been kind to it. During my research for the PHEV project, I beat the snot out of it, letting it run into the ground several times accidentally. Now it will fall below 12 if I leave Ig-on for more than a few minutes. Since I plug my car in every night and the PHEV charger also tops up the 12V, I haven't yet had to replace it. Probably do it before my next big trip though. I'm considering a small pack of A123 cells just like my PHEV pack has, that would lighten my weight in the back, and I'd probably be real close to my original weight at that point!

 

I have no idea what condition the OP's 12V battery is in. If the battery has like-new capacity (~35 Ah) and is fully-charged then I agree that the 12V battery can withstand 45 days of quiescent current draw and still start the car.

~0.020 A quiescent current draw x 24 hours / day x 45 days = 21.6 Ah

Hence, a new battery will be discharged around 62% with a 45 day idle period. For long battery life, it is recommended that the battery not be discharged more than 50%.

This also assumes that upon your return, you either charge up the 12V battery or else drive it sufficiently to bring the charge up over the next few days of usage.

A Toyota TSB on this subject recommends that the 12V battery be disconnected if the vehicle is stored more than 10 days.

If the OP's battery is in marginal condition, then it will definitely be dead at the end of the 45 day period.

 

i'm not arguing and i probably should start throwing a trickle charger on mine for best practices.

 

another method is to simply remove the top 15 amp fuse on the left side of the fuse box. there are 2 red 15 amp fuses. remove the top one. when you return, push it back in and you will be fine.

 

85,000 miles on my '05, and it's still the original battery. Stored for 4 months one winter.

 

What about the traction battery on a longer storage period?? I'm going to be away for 110 days and while I use a "smart charger" on my 12v battery whenever I'm gone, I'm concerned about the "big battery". Is it going to be OK for that length of time? I have a 2006 Prius.

 

lucky !

 

I was in Germany for three months, no problem. Just follow Pat's suggestion and Forcecharge HV Battery.

 

Easiest way to disconnect 12V, is to install a battery disconnect switch at the + terminal at the front ( charge,jumper) access point, under the hood.

I plan on doing this when my PIP arrives :cheer2:

 

I have a 2010. Ten DAYS is the max time to not drive the car before the battery won't function. This information comes straight from Toyota. My reaction - Wth! Solution is to disconnect the battery OR pull the "short pin" in the fuse box under the hood (as illustrated in a service bulletin - email me for it). Very Poor Engineering I'd say.