What are the symptoms of the battery dying?

I'd look into replacing the 12v battery first.

 

+1

Chris,
the conditions you noted are classic symptoms of the 12V battery needing
replacement.

If you're still on the OEM battery, they have typical service life of 4 years...
and you've gone six. :thumb:

Time to pay the piper.

 

Here is some info on 12V battery testing:

http://priuschat.com/forums/gen-ii-...y-check-without-switching-headlights-off.html

Good luck!

 

Your Prius has (at least) 3 batteries, with different symptoms.

The Fob Battery runs the doors and ignition functions If the door don't open or the car needs the key inserted to start, suspect the fob battery.

The 12v battery runs accessories when not READY, and powers the computers so you can start the car, as it runs down the HV Battery may spend a great deal of effort recharging it, leading to poor gas mileage, and the computer may become more and more confused, forgetting presets. Also when not READY, it may have difficulty with the power windows.

The HV battery has computers watching after it's every need. if it is not doing well, the instrument panel lights up like a christmas tree.

 

And let us know your findings.

 

I tried the battery test on my 08 but the display screen is different and doesn't allow me to hit the display icon, opening up the next series. is there another test?

mine is a #6, 2008

 

There is no need to hit a "display icon". Take a look at:
http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html
For the method I use to test my 2004 Prius 12v battery.

JeffD

 

Yes the graphics is for older models (04-05?) but the same procedure worked fine on my 09. Not clear which step you are having problem. Note in the instruction the "display switch" refers to the actual button labeled "display" on the side of the MFD, not the "display" word on the screen. If you still have problem please clarify exactly which step you can't do. There is always another alternative to invest in a digital multimeter which has become very affordable and is generally very useful. Good luck!

 

I'd like to note that the symptoms of the HV battery dying are as following:

VERY RAPID changes in state of charge. (green to purple in less then 3 minutes) or
You park the car with blue bars and turn it off, then next morning, it has 1 red bar.
You hear the battery cooling fan on all the time.

 

The voltage readings imply the battery is borderline. However keep in mind that error potentially exists in the readout, possibly as much as +/- 0.7V.

Nevertheless, since your 12V battery is six years old I recommend that you replace it now. This may or may not address the symptoms that you described in your OP. Regardless, installation of a new battery will reduce the likelihood that you'll experience a no-start situation in the near future.

 

Yep that battery sounds like it's close to end of life. I'd replace it soon.

Re your state of charge (SOC) dropping to one bar and the engine staying on (it will do that when the SOC is low). Can you think of any driving conditions that might have caused that low SOC. The one that most often effects me is if I start driving up hill from a cold start. I find that can run down the battery a fair bit in the first few minutes and then depending on where and how I'm driving it can take a while to get the SOC levels right back up there.

Anyway, do make sure you let us all know how it turns out after you get a new 12V battery.

 

4 years later. .. I have a 2005 with 232,900 miles. On my commute to work it always seems to stay at 6 bars SOC except one place where it goes to green at 7 bars.
Well this morning it randomly dropped to 5 bars, 5 minutes in to the drive.
Thought it was due to having rear defrost on. . Maybe? But then where it goes to 6 7 bars (due to braking down a hill at 6 mph) it went completely full!
And then while driving along after that 2 mins later @ a steady 55 it drains to 5 bars?? It has never done that and I drive this road 5 times a week.
Battery voltage after a long drive 12.2 volts no load. It's a optima battery and I have no clue how old it is

 

And just got my grid charger in the mail yesterday.. I'm almost afraid to use it now! What do I do? I hope the battery isn't dieing!
I also don't hear the fan running

 

As long as it hasn’t thrown trouble code using charger to SLOWLY overcharge it may repair it for long time. If fan doesn’t that is first thing to repair. Check battery temperature and/or use something to command fan on.

 

Well today on the way home from work it never acted odd or fluctuated. Started grid charging it today

 

Same as a dying cat. Won't get up and run, walks slow, makes a lot of noise, something stopped up.

 

my 2007 HV batt died @ 128000 mi. 2 cells were bad - it does the same thing a laptop battery does. You will get a couple of codes - can't remember what they were but it is a stretch to assoc them with the HV batt. A Techstream will show exactly which cells are bad.The dealer did that for me. The 12v batt went bad at the same time - about 6-7 yrs. They are rather pricey also. The HV batt is about $3000. at a dealer but there are options if you are handy or not - even just replacing the bad cells.