Replace 2005 12 Volt Battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Kirk05Prius, Jul 5, 2021.

  1. Kirk05Prius

    Kirk05Prius New Member

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    Bought used 2005 prius nov 2016. Almost 5 years I've owned, pretty sure my 12 volt battery is going dead.

    I replaced my headlights 3 months ago. They are both sporadically going off now. Flipping them off & on brings back for a very short time. & they aren't real bright.

    I spent $1,600 getting brakes done at mechanic shop. Now all my brake lights are lit up. Vsc, brake, traction control, etc.

    & my mileage is like 35 mpg vs normal 40.

    Three options I'm seeing
    1. Agm battery large capacity project someone posted. More work than I want to take on.

    2 self install Amazon ACDelco Gold B24R 24 Month Warranty Hybrid Vehicle AGM BCI Group...
    • $247.81$247.81
    3. Will price at Toyota dealerships hopefully open after the 4th of July. I'm about 4 hrs from home in Indianapolis.

    If i hadn't seen my dad's 2007 hybrid camry go electronically crazy when his 12 volt went out, I'd probably be alot more freaked out right now

    Anyone with recent price points/experience/advice for replacing gen 2 12 volt?
     
  2. bisco

    bisco cookie crumbler

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    i paid $210. plus tax at the local dealer. i doubt the headlights are a symptom of a bad 12v though. maybe a loss of a few mpg's as the hybrid battery tries to keep it charged, and the engine runs more to charge the hybrid battery.
     
  3. Kirk05Prius

    Kirk05Prius New Member

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    Just got back from Bill Estes Toyota.

    They Tested the battery. The battery was good. Thanks to Bill Estes.

    30 year technician told me to replace the hiid headlights with regular headlights. Computers & ballasts probably have water in them.

    Battery was gonna be $250 installed + tax. 84 month battery. Dealership seems like best deal for battery. Pep boys wanted $115 to install.

    Anyone point me to a thread to replace the hiid headlights with "normal" headlights. Thanks.
     
  4. pasadena_commut

    pasadena_commut Active Member

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    Not too long ago I bought one at the dealership and installed it myself. It wasn't difficult. The worst bit was loosening the nut at the negative post, as it faces "the wrong way" towards the back of the car, which makes it hard to reach. A tiny ratchet (about 4" long) worked but a normal size 1/4" ratchet (more than twice that size) was unusable in the same location.

    Just be sure that you don't let the hatch close while the 12V is out of the car or disconnected or you will have to crawl into the back to use the manual hatch release. That is awkward and uncomfortable.

    As you noted, MPG decrease is a symptom of a very weak 12V battery.
     
  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Oh dear... Prius brake maintenance has a few gotchas.

    If just doing brake pads clean up and relube, you want to disconnect the 12 volt negative cable, and/or make REAL sure the driver's door is not opened.

    If you're going to drain brake fluid, then you either want to have Techstream, OR put the car in "invalid mode".

    More info on those if you're interested. Simplest route: take it to a dealership, tell them the full story.
     
  6. PriusCamper

    PriusCamper Senior Member

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    Very best battery that will outperform all the others and only costs $100 is this one: https://ebay.us/vN4JsP

    If you decide to buy this one let me know and I'll post pics of the bolts and washers you need to buy at hardware store so terminals mount properly...
     
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  7. bisco

    bisco cookie crumbler

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    shouldn't the mech fix the brake lite problem for no?
     
  8. bisco

    bisco cookie crumbler

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    there are lots of hid threads
     
  9. bisco

    bisco cookie crumbler

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  10. Kirk05Prius

    Kirk05Prius New Member

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    Prius hybrids sales and service Scottsburg Indiana

    Prius specialty store about 90 minute south from Indianapolis.

    They changed the hiid lights over to halogen.

    I had a ghost code saying my catalytic converter was blocked. They replaced with aftermarket catalytic converter & gave me some $$s. My mpg was up to 41.5 with AC kicking in 91 degree weather. I was getting 38 or 39 mpg before.

    They got brake codes to go away.

    Overall very happy. But true test is driving it in the dark tonight.

    Definitely will be taking prius for further work to autobeyours.
     
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  11. bisco

    bisco cookie crumbler

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    you found a good one
     
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  12. Kirk05Prius

    Kirk05Prius New Member

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    Car drove great. Headlights very bright.

    All the way up to 43 mpg at one point.

    No warning lights on.

    COUPLE THINGS I LEARNED
    1. HID LIGHTS BAD DESIGN (my car has 205k miles)
    2. Smart key equipped Prius take a bigger 12 volt battery. I turned smart key off after reading how it can drain some 12 volt batteries.

    Hopefully i can get some trouble free miles. Although my tires are about in need of replacing.
     
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  13. Sebpercu

    Sebpercu Junior Member

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    Hi PriusCamper, can you give more information about the 100$ ebay's battery and installation ? I need to change my 12V battery.

    thank you
     
  14. PriusCamper

    PriusCamper Senior Member

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    Here's the link to the 12v: https://ebay.us/vN4JsP

    As for installation, the battery is slightly taller, so I rebend the hold down bar across the top of it, but you could also do this by adding a longer bolt to where it mounts in front of the battery, or by modifying or removing the metal tray the battery sits on top of.

    The existing terminals work fine on this battery as long as you buy the longer bolts below and sandwich the terminal between two washers that are slightly larger than each terminal:

    PXL_20210209_231231938.jpg

    PXL_20210216_005159433.jpg
     
  15. johnHRP

    johnHRP Junior Member

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    I always get original Yuasa or Toyota battery. They last much longer 7-9 years in the past. I heard yellow top Optima works too but not as good as Yuasa in long terms. For 3-6 years it may work fine and cheaper.

    This is the reading of my 12V battery in 3rd Gen Prius 2015 original. Without load 11.9, under load/headlight 11.3, full load heater, blower defroster 10.8 V, outside temperature 5C.
    I have smart keys, never have any problems since 6 years ago with original battery. I won't spend money on something still good.

    I don't believe chinese 12V battery that claims high capacity, etc. We don't trust them and they don't last as long as typical generic 12V battery. We still need AGM because it is on the trunk and next to passanger and HV battery
     

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  16. bisco

    bisco cookie crumbler

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    you should probably carry a jump pack if travelling beyond your 'car won't start' comfort zone
     
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