Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by 2009Prius, Mar 26, 2010.

  1. Starkie

    Starkie Junior Member

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    I tried using the information described in this thread to test the 12V battery.
    But the procedure is apparently for 2010 and below Priii and neither work in my 2011 IV.
    So I'll take my friend James' advice and invest in a mult-imeter.
    And check the 12V battery in my 2011 IV monthly via the jump ports in the PDU.
     
  2. akm3

    akm3 First time Lebowski'er

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    12.3 with everything off (Except the aftermarket double din nav system) dropping to 11.9 when I turn the lights on would indicate everything is good right?

    I ask because since the aftermarket double din nav system was installed, I see purple on my traction a lot more, the car feels 'heavier' or more sluggish, and my mpg seems to have dropped from 48-50 to 40-44. But that might be I'm not driving as carefully because I'm playing with the aftermarket double din nav system.
     
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  3. Starkie

    Starkie Junior Member

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    I tested mine with my new $39 Radio Shack multimeter (thanks for the tip, James).
    So easy to test with a multimeter.
    Just touch the red wand on the metal tab under the red, flip-top cap in the under hood fuse box.
    And then touch the black wand on the chassis.
    Mine read 12.85 volts with everything off and after the car sat for 4 days without use.
     
  4. Bronze84

    Bronze84 Member

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    Sorry to bring up an old thread but I didn't want to start a new one unnecessarily. I've just done this test on my 2008 Prius. First reading (idle) is 11.9v, second reading with load is 11.5v and in 'ready' mode it shows 13.9v - is this a healthy battery?

    Cheers

    Martin
     
  5. dorunron

    dorunron Senior Member

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    Martin,

    If you ran the test without the headlights on, or any other type of heavy load I would say your battery is definitely weak and should be replaced as soon as possible.

    If you ever see the triangle with the explanation point come on along with a loud long beep, that too is saying the voltage sagged below 11 while going through the start up process.

    I recently changed the 12 volt on our Prius. My numbers when I pulled the battery were about what you are reporting and I also saw the triangle once. Since I put the new one in my numbers are now 12.6, 12.3, and 13.9

    If you do change the battery, check the voltage of the battery with a digital meter. A fully charged 12 volt should read at least 12.6 volts. Our NEW Toyota "True Start" (OEM) battery measured 13.0 volts straight out of the box.

    The graph below gives you an idea of % of charge on the 12 volt battery based on measured voltage.

    Ron
     

    Attached Files:

  6. Britprius

    Britprius Senior Member

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    Martin knowing that you have just purchased your car I would charge the battery at leased over night at no more than 4 amps "the maximum charge rate for the OEM battery" because your car could have been stood for a few weeks and the Prius uses some current all the while and only charges at a maximum of 4 amps.

    John.
     
  7. dorunron

    dorunron Senior Member

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    Charging it may help, but I have a feeling that Martin will probably end up having to change the battery. If the car sat for a while, the chance of the battery being sulfated is there. Even with a good desulfator, he still may end up having to replace the battery.

    I am not saying not to charge the battery. What I am saying is that by charging the battery, it may only be a temporary fix. The real question is whether or not the existing battery will hold a charge.

    Ron
     
  8. emosca

    emosca Junior Member

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    The first time I tried, the directions given for entering the maintenance mode did not work on my 2006 Prius. With the car off, I put it in Park, engaged the parking brake, pushed in the Power button and then pushed the Display button. Nothing happened. The MFD remained dark. However, I tried again and this time I stepped on the brake when pressing the Power button. In addition, I activated the MFD by pressing the MAP button and then pressed on Display button. That worked.
     
  9. Terrell

    Terrell Member

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    Mine reads 12.60v with a digital multimeter with nothing turned on (battery is 4 years old).

    Reading the battery in Ready mode isn't reading the battery, it's reading the DC/DC inverter which supplies charging to the battery (14.67v on mine).

    Is there a built-in check that'll show the battery voltage on a 2010 that doesn't have the GPS system?
     
  10. Britprius

    Britprius Senior Member

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    Terrell 14.67 volts is a very high charging voltage suggesting the battery was in a low state of charge. That sort of voltage level into a battery in good condition (but low on charge) would represent a charge current of at leased 50 amps. A fully charged battery in good condition would show a charge voltage of 13.8 to 14.2 maximum.

    John (Britprius)
     
  11. ToyotaPrius2005

    ToyotaPrius2005 Junior Member

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    my battery still reads: (using MFD)
    14.3 car on ready
    12.1 car on (not ready)

    checking every so often now..

    original battery from 2005
     
  12. dorunron

    dorunron Senior Member

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    Sounds weak to me, especially if the 12.1 is accessory mode.
     
  13. Armacham

    Armacham New Member

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    I just tested mine today. Assuming I did it correctly I got 11.9 with nothing on, 10.3 with headlights on, defroster going and heater on full blast, and 13.9 with the car running. Sounds like time for a new battery?
     
  14. dorunron

    dorunron Senior Member

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    Sounds like your battery could use replacement. It might last the winter, or it might fail tonight.

    A fully charged AGM battery will read a minimum of 12.8 volts measured at the battery posts with no load applied.

    Battery SOC Chart.jpg
     
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  15. Armacham

    Armacham New Member

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    Thanks for confirming for me. I just bought the car, a 2008, a short time ago and I'm sure it still has the original battery. It looks like amazon has a decent price on the optima yellowtop right now so I'll order that and install it myself.


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  16. dorunron

    dorunron Senior Member

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    Make sure whatever battery you purchase is "FULLY" charged before you install it. Measure the voltage at the battery posts with a digital meter. The chart I posted above will give you an idea of what the measurements mean in relation to the "State Of Charge". Remember a fully charged AGM type battery will measure a minimum of 12.8 volts. Do not accept any new battery if it measures 12.6 volts or less.

    Finally, there have been numerous reports in the past few months where "new" Optima Yellow Top Batteries were being sold that are not fully charged. So, with that said, it is important that you check any "new" battery BEFORE you install it.
     
  17. Armacham

    Armacham New Member

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    Yes, I have a battery tender plus that I've used in the past.


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  18. w2co

    w2co Member

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    Yup our 06 prius (on 2nd 12v battery) is getting weak now, will not hold overnight and in the morning upon first startup the car gives the Red Triangle for an instant then comes ready when inv. kicks in. So it's on the verge of throwin a dtc. Obviously we need a new 12v battery, so in the meantime I just connect a 13.8V-14.2v variable power supply to the jump terminal up front in the fuse compartment (drivers side) for ten minutes before turning the car on the first time, this will charge the 12v batt up enough to get going for the day, it comes up perfect now.. just don't park it for 8+hours and you're fine. The problem is because as the lead acid battery ages (around 4yrs) it cannot hold the charge for long and will slowly drift down in a few hours especially in below freezing temps, and this is normal. Now onto another note I discovered by helping a stranded prius one day who couldn't start up (Red Triangle) and lights very dim etc.. so I jumpered my 12v batt to his (both cars off), which enabled his to come up then disconnected and off he went. A few months later I ran into this gentleman again and he said he actually got stuck again (same problem) but that time he got some kid in a hot rod who was all gung ho, he didn't shut his engine off and was even revving it when they connected to the front jumper terminal and he blew up the invertor! So please keep in mind these cars do not use the 12v battery to start the engine, rather it only needs the 12v to bring up the computers etc. and then it goes "ready" if all sensors are in range at POST (Power On System Test). By having that car running it caused voltage spikes from the brushes in his alternator, even more so if he's revvin it. No -the proper way to "jump" a prius with a low 12v batt is to have another vehicle next to it (turn both cars off!) and then just jumper his batt terminals over to either the 12v jump terminal up front, or directly to the batt terminals in back. And remember to connect the + on both vehicles first then the neg to the jump vehicle frame then the neg to prius frame last. This will protect the inverter from any voltage spikes.
     
  19. 32kcolors

    32kcolors Senior Member

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    Bumping an old thread but just so people know it works in the Gen III, follow the youtube video


    Function Check/Setting > Vehicle Signal > Battery


    Avoid touching the blue lines when doing the finger dance. You should be touching the areas below and above the lines. Keep trying repeatedly (more than 3 times) until you get to the service menu.

     
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  20. bruceha_2000

    bruceha_2000 Senior Member

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    My wife's 2006 is due for a new 12V ASAP. It is starting to do weird things such as beeping when the driver's door is opened even though it had just been shut down properly. Ignoring that noise yielded a dead 12V. And yesterday it threw an error on the screen related to putting the transmission in Park - even though it was in Park all night, I was checking the fog light I replaced. I think that is the same message I was getting before my '04 12V died. But that was after only 4 years. Almost 8 years on the '06 battery. Can't complain about that. Hopefully it will last long enough for a new battery to arrive.

    Bruce
     
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