12v Values, too low?

When my 5 year old battery hit 11.9 it really started to go down hill fast and that's with periodic maintenance charges.
Yours will too. Of course that period will be shortened greatly if you ever had to jump start the car as the battery becomes slightly sulphated then.
If the mileage is getting hammered its way due.
Soon you'll notice a big red exclamation point showing briefly on the dash when you start the car. That means the battery is dipping well below 11.5 volts and approaching death.

If I was the only one who drove my car I would not be concerned but did not want the wife to get stuck and have some helpful person jump start the car with wrong polarity and I get to go pick up my now totaled car all because the 12 volt battery was old and ready to leave me.

Nope, threw an Optima in it.

Next.

 

Your bat voltages Looks ok to me. Check the voltage after the car has set over night. If the voltage is down around 11.1 v. , I'd consider replacing the battery.

 

These were about the values I got just after replacing my battery, so I think they are okay. You will see a significant drop in MPG in the cold.

 

Cold battery? Brrr.
Deep Cycle Battery FAQ
Some good info here page pg 34: http://www.lifelinebatteries.com/manual.pdf

 

Ok, here is my .02 worth. It is based on my experience with our Prius and the 12 volt battery. IMO your battery is not FINE. It is borderline and weak. Yes, voltages do tend to drop as the temp drops. However, the voltages that the OP called out are definitely lower than a new fully charged battery would be at the temps the OP mentioned.

The OP may be lucky and make it through the winter with no problems. Or the OP may find one particular cold morning that when he or she goes to start the Prius the red triangle will momentarily light. Once that starts happening, it is only a matter of time before the battery will be needing jump starts. Jump starts are a whole different issue with the Prius and if not done right, can cause a four digit repair bill.

The OP asked for thoughts. Those are mine. I base them on personal experience with our 09 Prius. FWIW, I just changed mine recently. My voltages were also 12.1, 11.9 and 14.0 However on a cold Texas morning the red triangle lit. I checked the voltage again. 11.8, 11.5, and 14.1 I was also having to charge the battery at least every other week.

With the new battery I am seeing 12.6, 12.3, and 14.0 on those cold 30 degree mornings. Those are the numbers. I will let the OP make his or her final decision.

Ron

 

What brand was that new battery you put in? FWIW, a new fully charged battery should measure 12.6 volts or higher. It seems to me your new battery was not fully charged.

Ron

 

Dorun:

I see the identical numbers with my new Optima. 12.6---12.3---14. Those are good.
11.9 is the battery waving goodbye.

 

I have to amend my statement -- the second number (loaded battery) was 11.9. Unloaded it was 12.6 or so. I still expected higher than 11.9 under load, though.

To answer your question, it was an OEM battery.

 

Ok, that makes more sense now. Evidently, you are placing more of a load than most to get 11.9. Ign On with headlights off, a/c fans off and doors closed should be around 12.3 with that new OEM battery if you are getting 12.6 unloaded. Thank you for amending your statement.

Ron

 

IMO, absolutely!

 

Been there, done that. I saw the same thing right before the red triangle lit up. IMO, you really need to consider a new battery. When the triangle lights, it only does it for a second or two and the master alarm (BEEP) will sound off for a couple of seconds. Edthefox posted about that earlier in this string.

One other point. 11.9 volts is only 40% of full charge.



Like Ed said, your battery is waving goodbye.

Ron

 

There really is no "smart key light" in the Prius. There is a light which will light if you take the key fob out of the car while it is in ready mode. The light is amber and looks like a key laying horizontal with a vertical line through it. If that light is on while the key fob is inside the car more than likely one of two things is happening.

1. Something is interferring with the keyfob signal to the Prius (cellphone in same pocket, etc.)
2. Possible weak battery in keyfob



I suspect interferance more than anything if it is the light I described. If it is not the description you see or as illustrate above, I would suggest you consult the owner's manual for the correct terminology. Again there is no "smart key light" in the Prius.

Ron

 

Hmmm. The battery may be getting weak. Easy fix, but that light should not be on unless you remove the keyfob and then close the door. That is the only way I can make that light work. Are you carrying anything that might interfere with the keyfob? A cell phone gives my keyfob the willy's, and a pocket full of change doesn't help either.

EDIT: If you are getting out of the car while it is in "Ready" mode and closing the driver's door, the light will come on, and does stay on briefly after you return. I do consider this normal. Any other conditions I would consider abnormal. (End of Edit)

Here's a break down on the key that includes how to change the battery. They are real cheap at the local Walgreens. CR2032 I think is the number. Look on page #39 of the attached PDF file. Be sure to get a lithium battery.

My .02 on the Optima, many Prius Chatter's like them. However there have been reports recently concerning Optima's being on store shelves a long time and being sold not fully charged. I opted for a new OEM from Toyota. Mine came fully charged. It measured 13.0 with a digital volt meter. A Optima should measure 13.1 as per Optima Jim when fully charged.

It's your choice, I went with the OEM.

Ron

 

It's very easy to do if you have a set of jeweler's screw drivers. Just take your time and follow the instructions.

If you value the information I am sharing and you think it is worthwhile, you can click like on the post or post's if you so choose.

Good luck to you.

Ron

 

The owners manual address's replacing the FOB battery also.