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2002 Prius 12 Volt Battery problems

Discussion in 'Generation 1 Prius Discussion' started by posaunen, Jan 18, 2016.

  1. posaunen

    posaunen New Member

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    Hi everyone.
    This is my first post, so bear with me please. I've done a lot of reading on this forum, but haven't managed to find the info. that I'm looking for.
    I have never had to replace the original 12 Volt battery for my Prius, that is, until this year. I've now got almost 400,000 km. on the car, and the dealer wants $600 for a new battery, which Toyota doesn't even make anymore.

    I have had a fully charged "spare" battery in the trunk of the car for the last few months, and anytime it would not start, the extra battery was there and boosting the car was successful, until one of my family members hooked up the negative to the positive... Obviously, the car went dead.
    I had it towed to the Toyota dealer, where they confirmed that I needed a new battery. After reading on this forum about being able to use a Mazda Miata battery, at less than 1/2 the cost of a Toyota battery, I purchased one, and installed it. The Toyota technicians wouldn't touch it.

    The car started after installing the battery, but then it shut down after 5 - 10 seconds. After doing this a number of times, I was afraid of draining the battery, so I stopped. It runs on electric, however, so I got it back to the dealer, who now says that I need to replace a $20 fuse. The cost of this repair is upwards of $600 due to the location of the fuse, and the labour involved in replacing it.
    The technician also says that he can't do any further tests unless he replaces the fuse.

    It's fairly obvious that the electrical system received a fair bit of trauma, and I wonder if anyone knows if this fuse that needs to be replaced would have been able to do its job, and protect the rest of the electric components from being destroyed as well.
    OR, does anyone know of any way to check the rest of the electrical system, before doing this rather expensive repair?

    If anyone has had any kind of experience like this, or even theories and ideas, please let me know.
    Thanks so much!
    Angus
     
    #1 posaunen, Jan 18, 2016
  2. DRACO

    DRACO Member

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    Sorry to read your troubles.

    Did tech specify which fuse? If the 100Amp fuse, it is indeed difficult but not impossible to get to.

    But my main worry is the damage caused to the ECU/s

    Did the CEL turn on?
     
    #2 DRACO, Jan 18, 2016
  3. WilDavis

    WilDavis Senior Member

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    "…until one of my family members…" <------ Ah, I would venture to guess that there is the heart of your problem! It is A VERY BAD THING to reverse the polarity when attempting to jumper the 12V battery on a Prius! (even for just a split-second!) …as your helpful family member has proven to you! Sorry to learn of your problems, but a good perusal of some of the threads here in PriusChat might have saved you much wailing and gnashing of teeth! :eek: :eek: :whistle: - Good luck!
    PS: Go on, use "search" with "12V problems" in the search string! (…it will be most beneficial to you (and even to your helpful family member!))
     
    #3 WilDavis, Jan 18, 2016
  4. ChapmanF

    ChapmanF Senior Member

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    Hmm, I wonder what they meant by that. Gen 1 had two 12 volt battery options. The smaller one, number 28800-21050, looks to be about $173 from the online dealers I'm checking. The larger one, current part number 28800-31290, looks to be about $247. The -31290 is a darned nice battery ... 51 Ah in a small package.

    They have different sized posts, so it is easiest to replace whichever one your car had with the same one; otherwise you end up converting cable ends.

    That, of course, is the kind of job that sings out "DIY!" since the difference is so great between $20 for the part and $600 for paying somebody else to change it. Presumably it's the 100A DC/DC fuse, the only fuse in the car that's hard to get to. You need to loosen the attachments of the Engine Room Junction Block and get access to Fusible Link Block No. 1 from the bottom-ish. I think there are posts here from people who have done it.

    The fuse is, of course, intended to protect the semiconductor circuits ... whether it actually does in any one incident seems to involve an element of luck. No need to worry too much before you swap the $20 fuse ... then if there's more trouble, you'll find out, and if there isn't, you're good to go.

    After changing the fuse, I'd probably skip completely battening the junction block back down until I was sure the converter was ok, because if it turns out you need to get to the inverter, it's probably easier with the junction block movable.

    -Chap
     
    #4 ChapmanF, Jan 18, 2016
  5. posaunen

    posaunen New Member

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    Hi.
    He did specify that the part costs about $20, and nothing can be checked without getting that fixed.
    I'll ask them in the morning, but this sounds like the problem: thus the $580 in labour!
    Pardon my ignorance, but what are ECU/s and CEL?
    Thanks
     
    #5 posaunen, Jan 18, 2016
  6. posaunen

    posaunen New Member

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    #6 posaunen, Jan 18, 2016
  7. DRACO

    DRACO Member

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    ECU = are the many computer units in the car.
    CEL = Check Engine Light

    If that 100AMP fuse is the one and in fact blew, then it did it's job of protecting the car's ECUs. Hopefully.
     
    #7 DRACO, Jan 18, 2016
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Since the jump battery polarity was reversed, it is possible that the DC/DC converter in the inverter was destroyed. You won't know whether this is the case until the fuse has been replaced so that you can see what happens when you try to make the Prius READY.

    If the voltage on the 12V bus rises up to the normal 13.8V then the DC/DC converter is working. If the voltage is much lower, then the DC/DC converter has failed which means you just need to find and install a used inverter if you can DIY.

    If you have to rely upon dealer service installing a new part then you will be paying a fairly high four-digit price just for the part, not to mention a few labor hours on top of that.
     
    #8 Patrick Wong, Jan 19, 2016
    bwilson4web likes this.
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