What happens when 12v battery dies?

It will normally start giving you random fault lights, fault messages and fault codes. In this extreme cold weather it may not go to Ready mode or start the ICE.

 

on my Gen II, I seem to remember having to start twice because weird things would happen on the first try. Bad gas mileage not associated with seasonal change is also a sign.

 

it can do a million different things. on my '04, after 8 years, the sks stopped working and i had to press the fob button to unlock the door. if you're really unlucky, the car just won't start at the worst possible time.

 

The no tools method to test is to try the power windows in ACC, then try them again in Ready. If they were slower in ACC the 12 volt battery is weak.

 

Simple, it will go to the recycling heaven and be reincarnated. Believe me, you will notice.

 

If you wait too long, you will look goofy just sitting in a non functional car. Get the optima from elearn aid, it drops right in.
Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 + including Plug in

 

The SKS will stop working or barely work, or just work once. You can still get in with the mechanical key. The car won't start and the lights on the dash will be wrong but you won't quite know what's different, or what the different lights mean. You will push the start button again and it will change color, but now it won't turn off either. You will wonder if some staggering thousand dollar problem has just surfaced when all you wanted was to get to work. Just that morning the car will have started the same as always, but now dome light will barely glow. It will jump easily, (maybe)

You will come to understand that the stock Toyota battery is just to weak and small and will resolve to get an Optima yellow top fitted in there. It will be a nuisance to change over the battery terminals to take an adult size battery, but you will realize later that it feels good and was totally worth it.

 

It is such an coincident that I had the exact same problem on the day of your posting. I also have the 2010 model year too.
The battery in question was the original that came with the factory. It was a 50-month old unit. The weather was really cold (down to -30C at night) last week. I guessed the battery was close to its end of life and lost its cold cranking power under such severe weather condition. What happened below would probably answer your question.

After parking the car outside the driveway overnight, the door couldn't be opened with the key fob. I had to use the key to open the door manually. When I pressed on the Start button, the yellow engine light on the dash board came on. The car made a continuous and low whining noise but the system won't boot up. I pressed the Start button again in order to turn the system off but nothing would happen. The low whining noise continued. Since I had to leave the house, I just let the whining noise continue and locked the door. I returned about an hour later, the whining noise had stopped and the battery was drained completely.

So to summary the senarios:
(A) If the battery is totally dead, the car won't start and you won't see any light on the dash board.
(B) If the battery charge state is very low, you'd see the engine light on and hear continuous whining noise. You won't be able to stop the "booting process" or do anything about it until it drain up the battery.

My advise is to replace it after 4 years so you won't get stranded. I got the Optima Yellow and am happy with it.

 

I think my 12 battery is dying. I have a couple of weeks left on my 36 month new-car warranty on the car (I got my 2010 at the beginning of February 2011).

My question is is the 12V battery covered by the car's 36 month warranty? Does anyone know? The warranty book doesn't say anything about an exclusion for the battery. But I just called the dealer to schedule an appointment to have it looked at before my warranty expires, and the person on the phone said they weren't sure that the battery would be covered, they said batteries usually aren't. But, I didn't have a lot of confidence they knew what they were talking about. I'm wondering, because if it's not, I might rather go out and buy an Optima battery. But if the Toyota battery is under warranty, obviously I'd rather have them replace it.

A couple of months ago, my car wouldn't start one day, after sitting for 2 days. On the day I didn't drive it, I had the doors open for 1o to 15 minutes while I cleaned the interior. I'm quite sure I closed all the doors when done and didn't leave any lights on. But the next day, I tried to start it, and the interior lights were very dim, the motor sound you usually hear when starting (I believe this is the ABS pump) was very slow, the dash lights were dim, and the car wouldn't go to ready. Instead, I got a parking lock error message and some other errors. I tried a number of times, but it wouldn't go ready. I left the car, and took another. The next day, after several attempts, it went to ready. I continued having trouble getting to ready, it often failed on the first try, but usually went ready on the second try. And the interior lights were dim while trying to start, and dimmer when the ABS pump motor was running (more slowly than usual). After a long trip, it's fine for a few days, starts fine, then goes back to hard starting.

I put a volt meter on it. When running, the voltage climbs up to about 14.8 volts, indicating the charging system (inverter) seems to be fine, and tries to charge it. It starts fine after a long trip (2 hours) suggesting it charges. But I find if I leave the car parked for 2 to 3 days, the battery voltage drops to about 10 volts. It doesn't drop further, though. I left the car parked for 2 1/2 weeks when on vacation, and came back thinking it's never going to start now and then I'll clearly have a warranty claim, but it behaved the same: after a couple of presses on the start button, it went ready. I think one of the cells in the battery must be bad, and won't stay charged (12V batteries are made of 6 cells that are 2V each). I think one of the cells must go dead, while the other 5 are still good.

So my question is, can anyone confirm if the battery is warranted under the 36 month vehicle warranty? If it's not, I'd rather get an Optima, than pay the dealer top dollar to install a new Toyota battery. My other concern is I have kind of a long drive to the dealer, by the time I get there my battery will probably be fully charged and not appear to be bad.

 

I confess I am used to tires and 12 volt batteries having a separate warranty and not being covered by the automobile manufacturer.

Your Warranty Guide, however only mentions tires as having a separate warranty.
http://www.toyota.com/t3Portal/document/omms/T-MMS-10Prius/pdf/2010_Prius_WMG_0W20_lr.pdf
(Page 16 of the PDF, page 14 of the manual)

 

I looked there too, and don't see any exclusion for the battery, just for tires. So by that I'd think it's not excluded? But I agree I think batteries may not always fully be covered by warranties, and the person who scheduled my appointment said this. So I'm a bit confused. I don't know if I should believe what the service writer said on the phone (they sounded like they weren't sure), or assume it's covered since the warranty guide doesn't exclude it. I don't want to to back to get my battery replaced thinking it's under warranty, then end up with a big bill when I could have bought an Optimus and installed it myself.

 

Please let us know what happens at your appt.

 

Teacher says when a Prius 12V battery dies, and angel get's it's wings.

 

It's not chiselled in stone that you have to wait 'till it dies. My 2 cents: if it's done you good for say 4 years, at the least start researching, window shopping, for the replacement. And do the deed before it dies.

 

My nearly 5 year old 2009 Prius Touring Edition 12 volt started to come up on the diagnostic screen as ~12.o after sitting overnight, so on my day off I had AAA replace it. Less than $130, they did all the labor, warrantied the new one (for two years, I think) and I am a happy camper. If you don't know how to access the diagnostic screen, maybe we should start a new thread, whaddyathink?

 

It's not, but in my case since I'm hoping it will be covered by warranty, I think I may have a better claim if it's more obviously bad. That's why I'm wondering if the battery is covered by warranty. Or if it's a pro-rated warranty, I have almost no months left, so maybe it won't be covered hardly at all? Will let you know when I get there.

I don't know how to get into any diagnostic screens on Gen III, but I do have a driving monitor from my insurance company (I'm sure this could start a long side discussion, but this is a battery thread). It does include some diagnostic capabilities. I could pay extra for full access to scan codes, but even without that, they do give me this basic maintenance summary. The car isn't displaying any battery errors on the dashboard, but this thing is. This is my current status:


If the computer internally recognizes a fault it's not showing on the dashboard, maybe the dealer will also be able to read this and confirm a battery problem. I expect though after my long drive back to the dealer, the battery will be recharged and be back to green (that's how it's been going with this thing).

 

I notice one other thing too with this bad battery: once it's low, the car usually doesn't go ready the first time I press power, but usually does on the second. A few times, it's taken more than 2 presses. Even though I have my foot on the brake, the first try seems to end up in accessory mode (with a bunch of warning lights on, the same ones I think that are normally on in accessory mode).

I found this on page 438 of my owner's manual, this sounds a lot like what my car is doing:

This sounds like what I get. I put my foot on the brake, press power, get to accessory mode, then press power again, and get to ready.

Today, I checked the battery from the jump point under the hood before trying to start. It was at 10.22 volts (I haven't used the car enough in the last few days to keep the battery charged). The car only went into accessory mode the first time I tried to start, but went ready on the second attempt. The battery voltage went up to 14.83V within 5 to 10 seconds after starting, showing the car is trying to charge the battery. Oh, and the outside air temperature showed 6 degrees. So, even in the cold, this weak battery is still able to start the car. I've been carrying around a 12V battery borrowed from a lawn tractor (that's not being used in the winter), and a set of jumper cables, just in case it finally reaches the point of not starting. I haven't had to use it yet. And tomorrow is my appointment with the dealer to have the battery checked, so it appears I won't be needing it.

 

I think it'll depend entirely on who you talk to at the dealer, and how generous they feel. Batteries are generally considered consumable, and could be excluded by the "normal maintenance" clause in the warranty that also excludes things like spark plugs and wiper blades. On the other hand, if the person handling your checkup is feeling nice, they might still replace it.

 

That's exactly what I'm wondering. I see the exclusions for spark plugs, fuses, etc. but none for battery, so I'm not sure what to expect. My warranty book also excludes wiper blades. I hadn't considered that the "normal maintenance" might apply to the battery. I'd think there would be a more firm yes or no policy, rather than being up to the dealer, but I don't really know. We'll see.