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    Cory151 Junior Member

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    There seems to be a lot of discussion on when and if you should change your 12v battery. I figured people could post up what/if any change in how the vehicle drives or acts after? Ill start:

    Original 12v battery changed (Optima) at 130k, traction battery maintains a more consistent charge and isn't on 2 purple bars when I first start the car in the morning.
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    PriusCamper Can a Prius be a Campervan?

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    At the end of Jan2012 I bought a 2007 Prius with 102K and the original 12volt battery... Priuschat fanatics make me want to spend what little money I have left after the purchase on a new 12volt battery right away. But whenever I ask a Prius owner (other than one owner) they always brag about how they still have their original 12volt battery and all the people trying to get 'em to replace it aren't worth listening to...

    Their theory is that as long as you drive your car every day you won't have a problem. One guy said the state of Oregon has a 2004 Prius with 400K miles on it and still the original battery? Most everyone boasting of still having their original battery have priuses older than mine and with many more miles than mine. Yet Priuschat is the opposite of that?

    It'd be nice to hear from an expert on the pros and cons of adding a fresh 12volt battery? The best arguement of course is better gas mileage, but the only person who said they noticed that was the person who's Prius broke down because of a dead 12volt battery. Maybe she's just rationalizing all the money she spent at the Toyota dealer?

    My last car got 200K miles (75% freeway miles) and 9 years on the cheapest auto parts store 12 volt battery and I was also running two 750 watt power inverters off that battery. So I'm partial to thinking replacing a battery early is more about battery makers making more money than me having a car that runs better/gets better gas mileage.

    Anyways, I very much look forward to what the less paranoid / more knowledgable Prius experts think about this issue.
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    RobH Senior Member

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    I have no problem believing that a 2004 Prius with 400K miles still has the original traction battery (the big one).

    An original 12V battery in that old a car? Now that's a stretch. It's probably the first non-scheduled maintenance item on a Prius.
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    cnschult Active Member

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    if an optima was standard equip for our 12V could you believe than an optima could last that long for that many miles?
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    The Electric Me Go Speed Go!

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    I don't have a dog in this hunt, but I've hung around this website a long time. I don't see "regulars" or "Prius Chat Fanatics" recommending changing the 12volt capriciously or without reason.

    Often times people will post odd symptoms of operation and THEN people will recommend changing the 12 volt battery (or at least checking it )....which often IS the right thing to do.

    But I've never read a thread where anyone was recommending replacement for no reason.

    I would think if you are happy with your vehicle, aware of the age and risk you would take with any vehicle operating with an older 12 volt battery, by all means stretch replacement out as long as you wish.
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    uart Senior Member

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    Rob, my 2005 Prius still has the original 12V battery (date code Nov 25 2004), so I don't find it that much of a stretch. As for the 400k miles, that just implies it's been driven often, which is a good thing for 12V battery longevity.
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    wjtracy Senior Member

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    ...same here, my traction batt is usually either green or just into blue. I have not seen purple in ages....used to see it fairly often.
    Changed to Optima at 95K 6 months ago.
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    usnavystgc Die Hard DIYer

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    Let me start out by saying I'm about the tightest "tightwad" ever. With that said, I have a 2001 and I just changed out the 12V battery last October. I was getting intermittent error codes (CEL, TOD etc) but the car ran and drove fine with no depreciation in mpg. One cold morning (the first frost) I went out to start the car and nothing happened (no lights, nothing). I jumped the car and it started fine. Drove it around and no problem. After reading all of the posts about 12V batt problems, I decided to replace it with an Optima YT. Just out of curiosity the other day (about 2 weeks ago), I hooked up the original 2001 GS 12V battery to the charger to see if it would take a charge. To my suprise, it was at 95% SOC. I charged it to 100% for fun. I am confident I could put that battery back in and use it (for how long, no one knows).

    Since replacing the battery, the weird error codes are gone and don't come back so, go figure. It is known that lead acid batteries have a limited life and age is one of the major factors that cause them to fail.
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    Cory151 Junior Member

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    Did you have that batt load tested? I bet if you did the needle would start to dive immediately.
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    bobeast Junior Member

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    Its just a battery. I say 1) replace it when it no longer holds a charge, and 2) don't pay extra for the magic dealer battery (the one that makes your money disappear). I would also point out that this battery is not used to turn over the engine, so Its not unreasonable to expect them to last longer than would a battery in a conventional vehicle. As for these anecdotes about mileage changes, affects on the traction battery, mysterious error codes, and the appearance of unicorns....I don't buy em'

    fwiw. I'm at 130k+ on the original battery. So far, no unicorns have appeared.
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    usnavystgc Die Hard DIYer

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    No I didn't and that's a good point. I'll bet you're right. It probably has no useful life.
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    Cory151 Junior Member

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    Yeah unfortunately voltage without a load doesn't give a true measure of capacity. Very good input though.
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    Eileen82 New Member

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    [IMG]I would think if you are happy with your vehicle[IMG]
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    Artemus Clyde Frog Junior Member

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    Re the original post, other than the obvious, nothing has changed since I recently replaced my 12 volt battery in my 5-year-old 2007 Prius.

    By "the obvious", I mean that the car starts now. Prior to changing the battery, if the car had sat for a few days, I would get the red triangle and exclamation mark master warning light when I pressed the start button and the car would not start. The old battery had gotten so feeble that simply running the radio for 10 minutes with the engine off would deplete the battery enough to prevent the car from starting.

    Often, the reason a rechargeable battery needs to be replaced is that the reserve capacity has decreased significantly. Reserve capacity is a measure of how much power can be drawn from the battery before the battery can still provide enough power to do what it's supposed to do. Reduced reserve capacity is pretty much the same as "won't take a charge".

    Just a reminder here of what's been said many times on the forum, the 12 volt battery does not start the Prius. Put simply, it turns on the electronics which allow the car to start. The big high-voltage battery is the one that powers the motor that starts the gas engine.

    Also, I've seen posts re the 12 V battery lasting 10 years and that some folks are surprised about this. I'm not surprised. In my case I killed the battery in five years (61,000 miles). This was despite the fact that my kids have left the interior lights on many times and completely depleted the battery. In a rush to get going, I usually jump start the car, drive away, and let the car charge itself. Complete discharges are really bad for this type of battery. Also, in the case of a complete discharge a low-current slow trickle recharge is less damaging than the higher current recharge that the car will provide for itself.

    If I hadn't abused my battery like this, I'm sure it would have lasted significantly longer.
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    AllenZ Active Member

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    I changed my original 12V battery at 145K. It was weak, the voltage was lower and caused engine to run almost constantly, killing the mpg.

    Instead of buying from toyota or optima at $180+, I bought mine from Interstate Battery for a refurbished version for $30, adding adapter for another $15 or so total paid $45. It works very well so far at 157K.
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    Artemus Clyde Frog Junior Member

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    AllenZ, I'm totally impressed with the price you paid. I never would have thought of a refurbished option.

    Here's more of my story:

    I had already decided to get the genuine Toyota battery (part 28800-21171). I called my local Toyota dealer and they quoted me $242 (incl tax) for it. That's 242 for just the battery, not installation.

    I had seen posts here noting prices around $140 for the oem battery. I found prices in that price range online, but none of those sellers would ship the battery.

    Next I went to web sites for dealers near me and I found one that would let me buy at their online price and pick up at the dealer. They were less than 4 miles from my house. I went with them. Total cost $178 (164 plus tax). Saved me 64 bucks vs the other dealer.

    One last note, if you're at all handy with tools, change the battery yourself. I timed myself. 7 minutes to take the old one out, 7 minutes to put the new one in. That included taking out and putting away my tools and removing and replacing the trunk mat and all the stuff under the trunk floor. I guess you can add another 5 minutes for resetting the radio stations, clock, and auto up/down window. Important note: as early as possible disconnect the ground cable. It's really awkward to get to the ground cable clamp on the battery. Before I could get to the clamp bolt, I unbolted the cable where it attached to the car and wrapped it with a glove to keep it from contacting anything.
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    AllenZ Active Member

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    I think the refurbished part in my battery is only the plastic body. Everything inside is new. I also buy used tires at $15 - $25 a piece, with 80%+ thread life left. I use generic full synthetic oil.

    The maintenance cost of my 2004 Prius (157K+) is at $300/25K miles/year. Total cost of maintenance and depreciation is about $1000/year, and I plan to keep it at this level for next 5 years.

    I make a living by buying value products for my employer. I take educated compromise to lower total cost of ownership. That's my goal.
    imOCD4a_prius and babybird like this.

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