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12 volt batteries problems

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by KailuaPrius, Sep 13, 2010.

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  1. KailuaPrius

    KailuaPrius New Member

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    2008 Prius
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    is it a hassle to replace my 12 volt battery? went to the dealer and he said Toyota doesn't recommend me to replace it myself.
    has anyone replaced it themselves? any info will be helpful.


    Mike
    2008 Prius Gen II
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Here is a complete replacement with an Optima Yellow Top from elearnaid.com, replacement with the stock battery would be even easier.

    Prius 12V swap
  3. boppo

    boppo Active Member

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    I put the yellow top in mine and it was real easy and simple.
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you have a reasonable set of metric tools (sockets and box/open end wrenches) then you can replace the 12V battery. This project is a bit more cumbersome than replacing the 12V battery in a regular car, because you need to remove the traction battery vent that runs above the battery and also move the brake power supply which is next to the battery, for service clearance.

    When disconnecting the negative battery terminal you will find it is much easier to remove the cable where it connects to the body. Then swap the negative cable over to the new battery before installing it.

    Note the vent tube that runs from the battery to the body, and feel around so that you know where the tube should be reinstalled (through a grommet in the body.)

    When moving the brake power supply, you don't have to actually remove the wiring harness connector, just unbolt the power supply and move it out of the way.

    MSRP of the correct 12V battery is $139 but you will find that some dealer parts depts charge more, so you may want to call around to see who has the best price in your local area.
    1 person likes this.
  5. okiebutnotfrommuskogee

    okiebutnotfrommuskogee Senior Member

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    I put the Optima battery in mine and it was no problem at all.
  6. jreed

    jreed New Member

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    I installed the eLearn Aid kit and it took about 2 hours. There were excellent instructions but many steps (approx 30 individual steps). I would do it again over the dealer battery if given the choice.
  7. jayman

    jayman Senior Member

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    Yes, it is more complicated than a regular vehicle, but certainly doable if you're patient

    I used to back off and snug up the negative cable bolt where it attached to the unitbody, did this every spring and fall to ensure a good corrosion-free connection

    [​IMG]

    My 12 v battery with the VDC Battery Minder charge harness hooked up. The thing outlined in blue is the vent tube

    [​IMG]

    Speaking of charge, make sure the replacement battery is fully charged before installation! The Prius charge system is anemic at best, and if you do a lot of short-trip ops, the battery will become chronically undercharged

    This will result in much lower service life
    1 person likes this.
  8. vertex

    vertex Active Member

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    Battery replacement is definetly an easy DIY job. Purchase on from the dealer, it should run about $130. The Yellow top battery is better, but a little extra work. Seach this site, there are other options as well.
  9. richard schumacher

    richard schumacher shortbus driver

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    Only if you want to cobble up your own cable and mounting solution. There is no drop-in aftermarket replacement.
  10. vertex

    vertex Active Member

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    I thought that is what I said, buy it from the dealer, otherwise there is extra work.
  11. partsmore

    partsmore New Member

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    I changed the battery with an Optima already in my 2010 and installed a battery brain (Batter Minder) from batteriesareus . com

    The Optima d51 is Deep Cycle and will maintain a higher voltage under a load.
    They also sell the XPC-550 for higher capacity for audio and deep cycle demands,
    which I am going to order next for my stereo upgrades, and reduce engine charging demand / load while maintaining higher voltage.
  12. JimboK

    JimboK One owner, low mileage

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    Of course not. It cuts into the dealer's potential revenue stream.
  13. partsmore

    partsmore New Member

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  14. lrchome

    lrchome New Member

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    I bought the 12volt battery from SUN Toyota in New Port Richey Florida for $138 and they charged $12 to install. If you install yourself put 12 volts on the jumper terminals under the hood so you do not lose your computer settings.
  15. korat102

    korat102 New Member

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    Anyone found a non OEM battery available in the UK? They're surprisingly difficult to track down. Seems the usual suppliers only go by voltage and Ah rating. If you inform a sales droid that the thing they suggest won't physically fit and has the wrong terminal posts they look at you as if you're mad.

    My battery seems to have some life in it yet but after 5 years I'm starting to get a bit twitchy about it, especially after I allowed it to drain completely last year!
  16. Bob64

    Bob64 Sapphire of the Blue Sky

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    As long as you don't screw up (install the battery backwards). You should be fine...

    If you screw up, however, you can do serious damage.
  17. korat102

    korat102 New Member

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    Changed mine today, the original battery still had some life in it but wasn't holding a charge as well as it used to - better safe than sorry I thought. Tracked down a supplier of the D51 Optima Yellowtop recommended here. Everyone here is well aware of the procedure so I won't bore you with that.

    Something probably worth mentioning is that it's known as an Optima Yellowtop S 2.7 over here in the UK. The SR 2.7 is the same battery with the terminals reversed.

    Only extra work was the new ground lead and a new clamp for the positive terminal which I ordered at the same time from a different supplier. Got problems with the vent tube which I need to look into but apart from that it was a mostly trouble free installation.

    Only issue was the that floor piece didn't quite fit properly so I was forced to trim a little off one of the posts: This battery comes with a hefty plastic strap for carrying it around which doesn't lie flat. Although the floor initially fitted properly, over time it was pushed back up by the strap. Just trimming a few milimetres off the post cured that problem.
  18. okiebutnotfrommuskogee

    okiebutnotfrommuskogee Senior Member

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    Elearnaid removed the carrying strap from the one they sent me before sending it. They explained that it was in the way when the battery is installed in the car.
  19. korat102

    korat102 New Member

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    I considered removing the strap but decided to leave it in place. I thought it'd be quite difficult to heft around much less extract from that little cubby hole without the strap. Did you have any problems getting it in there without the strap installed?
  20. okiebutnotfrommuskogee

    okiebutnotfrommuskogee Senior Member

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    It wasn't a problem at all. I did remove the capacitor bank for the brakes and set it aside while I was doing the battery work. That gave plenty of room for the job.
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