Bad 12v or just normal

At 11.9v your 12v battery is low. I would start putting it on a trickle charger to see how high it will charge and how long it will hold the charge. You should have some time left before this battery leaves you stranded somewhere, especially if the temps warm up.

 

My failed battery, for a 2008 Prius, sits on the back porch and still reads 12.1 volts. But it would not start the car one day last week. This was on a 60 degree day after being running a number of errands. A new Yellow Top was the cure.

 

What does it read after sitting overnight in both ACC and IG-ON? (not READY) There will have been more parasitic loss, more time for battery to self-discharge and the evap check (soft whirring noise, about 5 hours after power off) will have run.

 

Same story here and the problem was caused by a bad 12v battery... MFD readings of 9.6v (no load), 9.4v (loaded) and 14.3v (charging) after sitting all night. Battery was replaced (new OEM) and all is well.

 

I note you wrote (new OEM). Would you be so kind as to post the part # of the battery you got? Also, did you get the battery from a Toyota dealer?

 

Toyota P/N 28800-21171 purchased at a local dealer.

 

Thanks for the info. Does you car have the SKS system on it? Is this a touring or a base model? I ask this whereas I can compare this number to other number's found for the OEM Prius battery.

 

Yes when the 12 volt battery is below 11.3 under load it will throw that red triangle momentarily. I say 11.3 because that where mine was when it first threw that triangle. I do not know the official voltage for that trip. It is not a CEL or any other code and does not get stored. Its just trying to get your attention the battery needs replacement.

 

Thanks for posting that, it makes me feel better about replacing the OEM battery on my 2006 just because it was about seven years old despite a 12.1 voltage reading and normal opperation with no codes or dash lights. With the battery that old when my wife said she thought a problem she had might be due to the battery I just ordered one before I even got home and checked the voltage. The problem did not recur and may have been user error due to post timechange drowsiness.

The direct fit replacement from optima is listed on amazon as:
Optima Batteries 8171-767 Yellow Grp S46b24r 450cca

 

I have a 2008 Touring Edition with SKS. The battery for the non-SKS is smaller and has a different P/N.

 

Thanks for the info. I have noted that there is more than two or three number's floating about. I also note that the number you called out comes up more often in reference to the touring model's. I was under the impression that the SKS equipped and the touring model's take the same battery, but am unsure at this point. I am aware that the non SKS takes the smaller battery. Thanks for the clarification and your reply.

If you happen to have a pic of the battery, could you post it please? I am interested to see if the marking's on it look like the battery here that I got from Toyota a couple of months ago. Or could you compare this pic to the one in your car?



Or does the top of your battery look this?

 

It's my understanding that the battery size is determined by whether or not the car has SKS... larger battery (SKS), smaller battery (non-SKS). Whether the car is Touring Edition or Base model does not seem to be a factor.

As for pictures, sorry but I don't have any and everything's all buttoned up.

 

I have the same understanding as you. What compounds things is I saw a add on a website that list's the part # you gave me. It called out a "touring model" on that site. BATTERY for 2009 TOYOTA PRIUS|28800-21171 That is why I mentioned that. I am not sure why there is a different part # on yours versus the one I got. I suspect the batteries are the same, just labeled differently, and possibly by different manufacturers. Don't worry about the pic's, I understand.

Thanks for all of the info and good luck to you.

 

All Tourings have SKS. The low end Touring package had roughly the same equipment as a midrange Standard.

 

Since a fully charged AGM battery should measure a minimum of 13.0 volts at the post's with NO load using a digital volt meter, I would be willing to say your battery is weak and should be replaced. Furthermore, if you are seeing the red triangle momentarily when you are entering "Ready Mode", chances are even greater that the battery voltage is indeed too low.

If it were my battery in my Prius, I would not hesitate changing it. For the record, I changed our's in January of this year. The voltages that I read on the MFD running the test that is recommended here on Prius Chat were the following. I also had once instance of seeing the red triangle upon entering "Ready Mode".

Accessory Mode 12.1
Ign ON Mode 11.8
Ready Mode 14.1

Once I changed the battery the test revealed these numbers.

Accessory Mode 12.6
Ign ON Mode 12.4
Ready Mode 13.9

I also note that as the temperatures have begun to warm here in the southwest I am seeing slightly higher voltages.

Accessory Mode 12.7
Ign ON Mode 12.5
Ready Mode 13.9

If you have a battery charger or tender, you might make it through the summer if you are in the northern hemisphere's, but if you are on the other side of the equator I would suggest you consider changing your battery soon as the cold temp's will cause the voltage's to drop further.

Good luck to you and I hope this info helps you in your decision.

 

I have not had any warning lights on in my car, but out of curiosity I checked the levels tonight after the car had been sitting 4-5hrs.

Accessory Mode 12.1
Ign ON Mode 11.8
Ready Mode 14.3

Based on the ranges I've found, it looks to be kind of mixed results on whether it is good or in need or replacing. Anyone care to chime in with their opinion?

Thanks

 

Read post #3 and think about what that poster said about the battery sitting on the back porch. Note the voltage they posted.

Also look at the values I posted above of what a fully charged AGM battery should read.

FWIW, where you are today is where I was right before I changed ours in January. The cold temps got mine. You might be lucky and make it through the summer, or it might die tomorrow. It's your call. One thing is for certain, when a battery dies, it always seems to happen at the worst time.