12V Battery Replacement-- A Preemptive Strike

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Rokeby, Apr 19, 2010.

  1. Rokeby

    Rokeby Member

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    Executive Summary: It takes ~40 minutes to replace the 12V battery.

    The whole story: Today I was doing some routine maintenance,
    wash/wax, vacuum, check tires, etc. I run at 42/40 and the tires were
    uniformly down 1 PSI since I topped them up a month ago. Very
    quietly the idea formed, "What about the spare tire?"

    I hadn't a clue. I had to mount the spare a little over a year ago. I ran
    it on surface streets for ~5 miles. I didn't check the pressure either
    before or after use. Shame on me. My excuse being that I was
    traveling to my mother's funeral and I was preoccupied and not
    processing peripheral external stimuli very well, if at all.

    So, after digging down thru the hatch area floor and the
    "miscellaneous gear " bin. I got to the tire, removed it, -- the valve is
    on the down-pointing side, of course -- and checked the pressure; 35
    PSI. Not good as inflation pressure is 60 PSI via the Owner's Manual.
    Pumped it up to spec with my elec. pump and started to button up.

    My eye fell on the 12V battery tucked away down on the right,
    snuggled behind the 12V brake emergency capacitor box and under the
    HV battery cooling/heating exhaust duct and a smallish piece of hatch
    area flooring. I'm thinking, "How easy is it to get that thing out I
    wonder?"

    PDR_0362.jpg
    The yellow is a label on the top of the 12V battery.
    The red plastic cover is over the positive cable end block.

    Many a time I have suggested to posters that they were in need of a
    new 12V battery. While an OEM replacement goes for $160,
    installation is often quoted at ~$90. I admit to thinking it is an easy,
    15 minute job. I decided I needed a truely "authentic experience."

    Easy? Well, kind of. 15 minutes? No, at least not for me.

    My owner's manual says nothing about taking the 12V battery out. So,
    I suppose Mother Toyota considers it a dealer job. At ~$90, that would
    not be true if I could at all help it.

    First off, you'll need 10 and 12mm sockets. A 3 inch extension is very
    helpful, though not strictly required.

    To ease the removal process, I decided that the elec. brake
    emergency power capacitor box and the last piece of the HV battery
    heating/cooling duct work should be removed before the battery itself.
    All-in-all, 8 fasteners need to be removed, and two loosened:
    Remove
    * Brake emerg power box - 2, 12mm bolts; 1, 10mm bolt
    * HV battery ducting - 1, 10mm bolt; 1, 10mm sheet metal screw
    * Battery hold-down strap - 1, 10mm boly; 1, 10mm nut.
    * Battery negative terminal wire to body (ground) - 1, 10 mm bolt.
    Loosen
    * Positive terminal clamp - 1, 10 mm nut
    * Negative terminal clamp - 1, 10 mm nut

    I attached an external 12V source to the terminals in the engine bay.

    My order of attack was:
    * Disconnect negative wire from body and securely tape over the end
    to prevent arcing.
    * Remove fasteners securing the brake emerg power box.
    * Remove fasteners securing the HV battery duct and snake it out.

    PDR_0366.jpg
    HV battery ducting and brake emergency power capacitor box unbolted.
    Battery can be easily lifted out after the wiring is disconnected. Black
    square at center top is the HV battery air vent exhaust. It exits into a
    space between inner and outer body work behind the rear wheel well.

    * Remove fasteners securing the battery hold-down bar.
    * Loosen fastener on positive post.
    * Remove positive cable from battery.
    * Remove battery
    * Loosen fastener on negative post.
    * Remove ground wire.
    * Remove vent tube from old battery.

    I then reversed the order to get back to the initial condition.

    At a determined, safety conscious rate of work, keeping track of
    fasteners and where they came from, it took me 40 minutes, start to
    finish. Don't know if that's good or bad. But it sounds like the dealer's
    $90 installation fee represents 1 hour of shop/tech time.

    So, now we know.

    Other discoveries:
    * The 2008 Owner's manual says that a wheel chock is needed to
    stabilize the car when up on the jack. Yet it is not provided in the OEM
    equipment. What's up with that? I checked the Owner's Manual when I
    mounted the spare last year, but this tidbit escaped my attention. I
    guess I was lucky; the road was flat and level.
    (I'm hoping I can find one/a pair that will fit in the "misc. gear" bin or
    the triangular storage are to the driver's side of the hatch floor.)
    * The HV battery heating/cooling exhaust duct has a cutout on the
    back side, hidden unless you take the piece out. It is right next to the
    12V battery. I guess that this is a "good enough" effort to provide
    some heating /cooling tho the 12V battery. As the air would have
    already passed around the HV battery, it it's rapid effectiveness is up
    to question.
     
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  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Did you replace the battery with a new one, or did you remove and reinstall the old battery just for fun?

    I suggest that it is more important to tape (or otherwise protect) the positive cable terminal connector after it is removed from the battery, in the instance where you have an external 12V source hooked up. Other than that suggestion, glad to hear that you had success with your battery work.
     
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  3. Rokeby

    Rokeby Member

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    Patrick.

    I took out and replaced the same battery. I don't consider it "old" yet
    at a little over 2 years service. I consider the exercise to be "just for
    info."

    In retrospect, I can appreciate your comments on the positive battery
    cable. I only had the red cover off when I loosened and removed the
    cable from the positive battery post. I immediately put the cover back
    on, even though the battery was not hooked up.

    At the time, it seemed to me that the thickish battery cable and the
    connected smaller cable bundle leading to the capacitor box precluded
    the positive cable end from flopping around much. The thin negative
    (ground) wire looked like a real risk to do so.

    I admit that I may have been wrong, or perhaps just not thinking
    things completely through. In the future, when I have to run through
    the drill for real, I will also shield/insulate the positive cable end if I
    use an eternal power source.

    Thanks for you comments. :)
     
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  4. roderunner

    roderunner Junior Member

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    So what happens if you don't have a spare 12v battery, and you disconnect the and pull out the battery to check fluid levels?
     
  5. boppo

    boppo Active Member

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    it a sealed battery, so you can't check the level. if you pull it out you will loose all your setting.
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    You just need to reset the following:

    1. Driver's window auto up/down
    2. Radio station presets

    The trip odometer reading and MFD mpg may be lost. The fuel gauge will show a blinking one bar after power is restored and the car is started, until that system figures out how much fuel is in the tank.

    The 12V battery is absorbed glass mat, so you don't need to check fluid level. There is little or no free fluid within.

    If you want to look into the battery, you need to peel off the label on the top using a single-edge razor blade (the label has a warning printed on it, not to remove.) The label covers a translucent plastic cover over the six cells. The cover can then be removed and you can look into the cells.
     
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  7. roderunner

    roderunner Junior Member

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    In reply to Boppo - the following comes from another thread.

    Prius Auxillary Battery Not Maintenance Free
    Toyota claims the auxillary battery is maintenance free since it is a sealed lead acid battery. Not true! The battery is vented to exterior atmosphere. With over 200,000 miles of Toyota hybrid experience, I suggest removal of battery annually to check each cell for elctrolyte level. With a normal charge system voltage level of approx. 14 volts, there will be a small loss of water vapor through the vent line due to normal charge-discharge cycles over time. When the electrolyte level gets well below the top of cell plates the battery efficiency drops off and may even go "open circuit" where it will not accept a charge. Ignore instructions on battery "Do not add water". Peel off lable on top of battery and pry translucent plastic plate off. By lifting small rubber caps on each cell one can then determine if distilled water should be added. Approx 3/8 - 1/2 inch above top of cell plates is adeqate. When replacing translucet plate, snap into recess area so it is flush with battery top. Toyota denies that any battery maintenance is required. The vent line is a safety requirement to avoid possibility of a faulty charging system over-charging a sealed battery (not used in Prius models) and exploding it in passenger compartment. Unlike other models using true sealed lead acid batteries, the Prius uses old technology which requires at least minimum annual inspection depending on vehicle use and climate.
    Dave Weaver (Prius 200,000 + miles)
     
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If your battery is AGM, you certainly do not want to add water above the cell plates. An AGM battery has white fuzzy mats between the lead plates, and you can see this fuzziness when you look into the cells. Typically an AGM battery has no free liquid, so you can tip the battery over and nothing will leak out.

    If your battery is the traditional liquid acid type, then the advice in post #7 has some validity.
     
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  9. whodat

    whodat Member

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    Just curious has anyone had experience adding water to the 12V aux battery?
    Thanks
    Dave
     
  10. tsteineman

    tsteineman Junior Member

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    Roderunner,

    Finally replaced my battery after 6 years.

    HOW do I reset the drivers side window to open/ close automatically? [email protected]

    Thanks.


     
  11. hpartsch

    hpartsch Member

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    So is there any way for used prius buyers/owners to recognize how old their battery is? I remember quickly looking at the top sticker on mine, and could not find any type of date.
     
  12. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Manually hold the button to roll the window up and down (one full cycle).
     
  13. andyprius

    andyprius Senior Member

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    I have just changed my battery again, about the 3rd. time in 6 years. Patrick mentioned before that he had added 1 oz to each cell. I added 1/2 oz to each cell then closed it up and put it on a trickle charger (500ma) I was suprised to see after I took the plastic plate sealing the cells that there was a small amounts of droplets ( 2-3)scattered just on top and under the plastic strip. Before doing any of this I checked the battery with a multimeter and surprisingly it read 12.83 open volts. So it still looks like a pretty healthy battery. :rockon:
     
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes. If your car has the original equipment GS Nippon Denchi battery, there is a date code. See my photo and note the date codes of 061200 on the top battery (Dec. 6, 2000) which was the original equipment battery in my 2001; and 171203 on the bottom battery (Dec 17, 2003) which was the original equipment battery in my 2004.

    Also note that the battery terminal polarity is reversed on the two batteries, because the Classic battery is mounted on the left side of the trunk while the 2G (and 3G for that matter) battery is mounted on the right side of the hatch.
     

    Attached Files:

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  15. hpartsch

    hpartsch Member

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    I changed/checked the date, 09/17/04 so I guess it was about time to replace this old battery. Plus with the diagnostic it was showing <12 and I was getting really low mpg.
     
  16. GRRtinybattery

    GRRtinybattery New Member

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    Thanks for that.
    Unfortunately your post did not show up when I searched for "remove 12 volt battery"!!
    By the way one does not have to remove the power assembly but one does need a log extension for the ratchet socket!
    Grtiny
    Prius t-spirit from new august 2007.....Flat battery every 6 months since!
     
  17. seilerts

    seilerts Battery Curmudgeon

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    GRR, Optima sells a battery in your country that is a drop-in replacement, model YTS 2.7J. If your battery goes flat every 6 months, first of all, why does that happen? And second, if it goes flat often, then install this Optima, which is 100 times more tolerant of being run flat and recharged compared to the Toyota one.
     
  18. cjcj1949

    cjcj1949 Junior Member

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    It is easy to undo the bolts that hold the brake power supply and move it out of the way. The official workshop manual shows that it is not necessary. Like most jobs, doing it the first time is the most difficult and moving it out of the way makes it easier to see what's going on. I found it easy to remove the awkward screw that hold the vent duct in place, but dropped it twice while refitting. My magnetic socket wasn't magnetic enough. I think I will try sellotape inside the 10mm socket next time, as fishing for the screw with a magnetic pickup is a bit uncertain.

    I also had to do it all again, as I thought the vent end fitted to the body, of course it doesn't.

    Here in the uk, the battery is fitted free at the moment. At some dealers it is cheaper to get it fitted than to buy it. £90 Jan 2012

    The new battery is a Yuasa AGM which is 13.20V open circuit when fully charged. Mine was not fully charged, but I'm not sure that matters very much.

    The original battery seems to be a mixture of AGM and normal technology. It is 13.0V open circuit after charge, but there is a lot of liquid in the battery. It is not all absorbed. If anyone has the manufacturers spec, I would appreciate a link.

    I don't understand the problems that you are having in the States. I have discharged my battery to below the point that the computer fails. If you then turn off the load, the battery quickly recovers to enough volts to start the computer.

    Obviously you get in the car, put your foot on the brake and hit the start button. It takes about a second to get the HV battery charging the 12V one.

    The major difference in the uk, is that we do not have the smart key system fitted. I do not know the current draw of the system, but it can easily be disabled.

    The current draw of my uk car is around 15ma. So thats 360mah a day or about 2.5aH A week. A new fully charged battery should last 10 to 20 weeks when not used.

    It is possible to buy portable chargers from radio control people. They have gone over to Balanced Lipo mainly and there are many chargers available cheaply which will charge to 14 or 15V. They can be charged from small 10AH batteries that are available from your local shop that sells small electric vehicles for people who have problems walking. The batteries have to be reycyled and if you promise to recycle them eventually you can get batteries that will recharge your 12V veru quicly.

    I used to use solar, on my last car whch gave 200mah for about5 hours inthe summer. In the summer it might improve mpg as the DCDC convertor will wait longer to start the battery.

    Thanks for all the help. These forums are amazing. When you get stuck. You just google it.

    If we keep the 12V battery fully charged, we have achieved a cheap and reliable plug inPrius. I seem to get better mpg from a fully charged battery.

    The Prius is the best car I'v ever owned.
     
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  19. AzWxGuy

    AzWxGuy Weather Guy

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    All these aux battery discussions got me inspired to check my own. I did the built-in test with the MFD, and after a 24-hour sit the battery voltage reads 11.9V. Cycled the Power button and the battery voltage briefly drops to 11.1V and then rises to 11.6V. Not good numbers according to the group consensus. Next I pulled panels and extricated the battery to inspect further. The date code indicates that this is the original battery, 251007W, or October 25, 2007. I bench checked the voltage again with a DVOM and it reads 12.38V with no load. I think a new OEM battery purchase is in my near future. I haven’t noticed any electrical/electronic wackiness yet, and MPG for mostly highway miles is holding steady at 47.3mpg. The regular 12V batteries in my other vehicles only last about 3-4 years anyway, so it is about time.
     
  20. tv4fish

    tv4fish Member

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    This may be/probably is redundant ? but these are the "step by step" instructions that I did when I recently replaced my 12V battery in my 2005 Prius.

    I bought the Optima Yellow top battery (with the adaptor kit)?. The "adaptors" are kind of "hidden" in the slots on the sides of the new battery.
    1) Make sure your "power" button is off
    2) Attach another 12v car battery by using jumper cables to the jumper battery and then to the jumper connectors in the fuse panel under the hood.
    3) Then you need to "get at" your existing battery - you need to first remove the rear deck so the spare is exposed - then remove the battery panel on the very rear RH side.
    4) You will see your battery on the "outside" and a fairly large "black box" sitting just to the left of the battery. Remove the bolts that hold the black box brackets to the frame of the car, not at the black box. The black box can than be swung out of the way.
    5) There is a dark red plastic "cover" over the + terminal of the battery - it is held in place by 2 press-in clips on the sides - remove that.
    6) Carefully remove the battery ground (-) strap from the car frame - again,- keep in mind that there is 12v on the system - so try not to touch your wrenches, etc. to the frame.
    7) Remove the (+) battery cable from the battery - same warning as above.
    8) There is a black battery hold down strap that has to be removed - one bolt on the left of the battery - other on the RH side - the one on the RH side won't fall down - just remove the nut on the top. Then swing the hold down strap out of the way.
    9) There is a black plastic air duct that needs to be removed in order to get the battery up and out of there - just 2 bolts -one at the front of it and one on the outer side at the back of it.
    10) You should then be able to lift the old battery up and out with the battery strap.
    11) If you DID get the "older" style Yellow top, you will have to add the adaptors to your set-up - the main one is for the (+) battery terminal - put it on the cable first (bolt up from the btm) NOT onto the battery post - as it only goes on the post one correct way.
    12) Make sure you get all the little pieces out of the sides of the new battery - there is a vent adaptor in there also.
    13) Then drop the new battery in the hole - make sure it sits all the way in - mine wanted to "rock" a little to start with.
    14) Then put the black plastic duct back on
    15) Attach the ground cable, the positive cable, battery hold down, etc. and pull off the existing vent fitting and replace with the one in the battery kit.
    16) Then just reverse the dis-assembly process.
    17) Unhook the battery up front and you s/b A-OK.
     
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