2010 II 12 Volt Battery Dead After 17 Days of Parking

I'm not sure I want to push the envelope on this, but my Prius has been garage-bound for 5 days now due to tire issues. When I opened the drivers door to get something today, I heard the brake pump pre-pressurizing, so the aux must still be good. I believe the hybrid battery was only about 4 bars when I parked.

I also notice on a different night that the rear overhead light was on even though the car appeared to be closed up tight. After opening and re-closing all the doors, the light went into the normal 30-second timeout and shut off. Might have a weak connection, or the doors weren't shut tight enough?

 

If you walk by the car with the SKS fob in your pocket the interior light will come on - perhaps you had walked by it just before and not noticed it turning on?

 

Entirely possible - I wonder what the range is, if you left your "keys" on a hook by the garage door, would that be far enough away to keep the light off?

 

My 2010 Prius is doing the same lame dead battery stunts. I am going to invest a lightweight jump start back ( $60), then crawl throught the back and open the back hatch. Actually the short fuse deal sounds best. The car is still great but they should let buyers know about this issue since most of us are used to cars that can sit for months and still start. Then again Toyota is slow to disclose problems

 

I have a 2007 Prius with this problem. Let me give you the benefit of my experience and research. Most people who encounter a dead 12V battery, especially with a young battery, assume that they left a door open or a light on. But Prius has 2 problems that are encountered frequently, and several that occur less often.

FIRST, the Smart Key and the Prius communicate constantly (what they talk about, I don’t know). This will drain the 12V battery in as few as 3 days (longer for newer models) and eventually the Smart Key as well. The solution is to not keep the key in a convenient location near the car, but to store it further away. Toyota says 10-12 feet, but I found this inadequate and keep the keys in a cabinet 25 feet away. There is a button below the dash, next to the steering column base, that can be used to turn the Smart Key System off, but due to the second issue I describe, this will only buy you time, not solve the problem. Because the SKS is an important part of the Prius’ anti-theft capability, I find it a worthwhile trade-off. Your post indicates that it is more difficult to turn off the SKS in the 2010 model, but the real problem is the one I describe below.

SECOND, Many (all?) Prius have a constant small electrical drain when parked, from 0.1 to 0.65 amps. This will drain the 12V battery in 10-12 days. This appears to be caused by ECUs (electrical control units) that do not enter sleep mode properly. The Prius has many ECUs, so you will not be able to figure out or access the ones causing the problem (it might be several). If you have this problem, you are stuck. Additionally, once the battery is drained a few times, it will go bad. Unfortunately, the ECU issue is a design problem that Toyota has not addressed. I’m convinced that it is a more common problem than people realize, as most people don’t park their cars for weeks. When they do, and return to find a dead battery, they assume that they left a door open or a light on, etc. Toyota Service will assume this as well. Only people who encounter the problem time and time again persist in getting a better answer, and it is an answer that they do not like. It took me lots of research and 5 visits to Toyota Service before they owned up to the problem; still they say that my driving habits (not operating the vehicle for 2 weeks or more) are not “normal†and the Prius is designed for “normal†driving habits. Toyota says all Prius have this problem, but they don’t call it a “problemâ€. This is the problem that my Prius has. I wish that Toyota had owned up to the problem sooner. I would have been PO’d, but I would have been saved years of aggravation and two occurrences of returning to parking lots late at night to find an inoperable vehicle. In the beginning they told me I was the problem, then they changed the battery, then they changed the battery again and suggested that I trade it in (at 30,000 miles), and finally told me the Prius is designed this way and my driving habits aren’t “normalâ€. In terms of how PO’d I became over the years, I would have been much happier if they had told me what the problem was in the beginning (not to mention how nice it would have been if they had told me BEFORE I bought the car). As it is, I have lost all faith in Toyota’s service honesty. This issue is not addressed in the manual (2007 or 2010).

THIRD, there are some problems encountered less frequently. A few people have encountered brake pedal switches that don’t turn off when the vehicle is parked. Toyota Service should be able to find this if they look for it. On older Prius models (I don’t know about newer ones), the carpet in the hatch area can gradually slip forward and prevent the hatch from latching, even though the hatch looks closed. A couple of people have found intermittent electrical shorts, which are difficult to diagnose; this appears to be a very rare problem.

Over the years, Toyota has provided better 12V batteries for Prius, but no battery will keep a charge if it has a constant drain on it. Fortunately, we have two vehicles. When the Prius will be parked for lengthy periods, we turn the Smart Key System off, attach the 12V to a trickle charger, carry an emergency back up supply (make sure that the clamps will fit on the small Prius posts), and we NEVER leave the Prius at the airport for longer than 3 days. I especially would not recommend this vehicle for elderly folks who drive only occasionally.

I hope that this helps. At least don’t assume that you are the problem.

--- Ento ---

 

I installed a toggle swtch to shut the battery off

 

Install a battery switch

 

To preclude this problem I keep the interior and trunk and door lights OFF

 

With ref to the 1st. para. I installed a toggle swich in series with the ground connection.

 

Now that is interesting! So Toyota has finally attempted to address this problem. It only took NINE years. Now if I had a 2010....

 

Mike, you have been lucky. If you search PC you will find this problem occuring hundreds of times.

 

Except......in many cases it was thought, that in shipment problems occured, ( a crewman listening to a radio, on a different car, every day) cars leaving the dealership with defective batteries. Batteries NOT being charged before sale. Most, if not all dealerships do not have the proper charging systems ( with load ) Some, IF, they had it would not use it, or would not know how? after all a new battery only cost (them) < $100 Probably in 50% of the cases it is the customers fault BUT only because Toyota has not explained how really PUNY the battery is. Boils down to: All Toyotas fault! :cheer2:

 

The dealer is not capable of properly checking the 12V.

 

What kind of car do you have?

 

No not really, you only have to use the mechanical key, put the rear seats forward, crawl forward ( take shoes off first ) Oh, go back and get flashlight, crawl in again, try and release cover, will not release? to hell with it, now lift small somewhat triangulat shelf protecting battery access, can't remove it? Oh that's right, that little cover does not come out unless trunk floor is removed, OK, I'll do that. Oh can't remove trunk floor because carpet is on top, so remove carpet, go back and get flashlight, now cannot remove trunk (main cover) because I am laying on it. To hell with the whole thing, I will call the dealer! Seriously, install a battery switch AND ( very important ) buy a small battery, for underhood connection so you can get access to car door, trunk and start car. Step 25: Disconnect emergency 12 V battery :cheer2: P.S. Do not store spare battery in tire compartment

 

Very interesting post Ento, I didn't realize that the parasitic drain was 650ma. You keep this up and you are going to stir up all the Techies and they will be quibbling for weeks.

 

This last winter I parked my 2010 Prius III for 15 days and had no problems. This summer I left for a trip and parked for 18 days and came back to a dead battery (the parking lot attendant brought a portable jump starter, which I connected to the jump points under the hood and got restarted easily). I always carefully check the car before I leave to make sure no lights are on, so I am sure that this is the same long-term "dead battery" problem others are describing.

I went to the dealer and their advice to me was to disconnect the negative terminal from the 12v battery in the rear whenever I won't be using the car for >2 weeks. I love my Prius, but having to disconnect the battery whenever I go on a long-term trip is a real bummer.

Is it possible for me to reprogram the smart key system (SKS) to "off" by myself without having to go to the dealer? I wonder if this might buy me a couple more days parking...

 

this is interesting because I go oncall for work and won't drive the Prius for a week. I'm guessing I won't have problems after just a week.

 

Probably not, and not everyone has problems leaving the car for longer periods. Some people have posted that they left their cars for over a month with no problems whatever.

If you are uneasy about it try to have some way to jump it using the under hood connector. You don't need standard jumper cables, #12 or #14 wire should be more than big enough because the 12V system doesn't run the starter. You just need enough current to boot the computers and run the brake booster pump for a few seconds.

 

hey thanks tumbleweed. 12 gauge wire huh? we have some at the shop. I'll keep it in mind.