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Replaced aux batter now car acts like it's dead

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by TooHuge, Jan 10, 2016.

  1. TooHuge

    TooHuge New Member

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    So I recently had the auxiliary battery in my 2008 Prius replaced after fighting with winter startups for several years. I took it to my usual shop rather than going DiY because, well, frankly I didn't want to deal with it myself. Which may have been a bad move because they didn't hook it up to a charger to keep the computer alive while doing the swap and now my system is acting wonky and they're clueless as to why.
    Basically the car behaves as if the battery is almost dead. On startup the dash lights and display don't come on and when I turn on the headlights the touchscreen dims. These are all things I dealt with when I had the old battery, except now the touchscreen keeps going back to the trip info screen.
    I put it in diagnostic mode and the battery reads at 12.8 volts idle and 12.4 in acc mode. With the engine on it bumps to around 13.9. So It appears that the battery is charged and good.
    I went to battery compartment and unplugged the accessory connector since this is the go-to response to the no-dash issue, and the dash comes back on the next startup but the lights still dim when the headlights are on. Then when you turn it off and back on again, the dash is once again gone.

    Has anyone dealt with this problem after swapping a battery? My next step is to take it to Toyota service, but they charge an arm and a leg so would really appreciate an alternative solution.
     
    #1 TooHuge, Jan 10, 2016
  2. bisco

    bisco cookie crumbler

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    welcome! how many miles on her?
     
    #2 bisco, Jan 10, 2016
  3. TooHuge

    TooHuge New Member

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    Thanks. A lot, my odometer isn't accessible right this second bit I wanna say around 135,000 and some change.
     
    #3 TooHuge, Jan 10, 2016
  4. Mareno Rathell

    Mareno Rathell Junior Member

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    I had that issue when installing a new battery. Turns out I needed to put the new battery on a charger to top it off before installing it in the car. Seems as though the battery sat on the shelf too long and needed to be topped off. Wouldn't of been an issue with most cars but as we know the Prius is a special beast.

    Also for some reason you need to push the start button on and off a couple of times after installing the new battery. I think there is a particular suggested way to do it...... meaning when you foot is/isn't on the brake pedal when pushing the start button.
     
    #4 Mareno Rathell, Jan 10, 2016
  5. bisco

    bisco cookie crumbler

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    perhaps a check of the battery connections, including the negative to body point. and press hard on the brake when pushing the power button. does the 'ready' light come on?
     
    #5 bisco, Jan 10, 2016
  6. ChapmanF

    ChapmanF Senior Member

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    Interesting puzzle. I would not rule out a high resistance connection somewhere in the power distribution wiring, causing a voltage drop across the wiring under load, while the battery voltage itself is ok. If that's what it is, it has to be in one (or more) of the power distribution circuits not including the circuit the MFD uses to sense battery voltage, since it is sensing the undropped voltage.

    If that were the hypothesis, pursuing it would just be a matter of looking at the wiring diagram manual starting in the power distribution section, eliminating the circuits where the problem isn't, and finding the locations to strategically test voltages to spiral in on where it is.

    Interesting. What do you mean by "the accessory connector", and what's the source for that being the go-to response?

    -Chap
     
    #6 ChapmanF, Jan 10, 2016
  7. The Electric Me

    The Electric Me Go Speed Go!

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    I'm also curious as to what you mean by accessory connector?

    I'd also start to fear that perhaps you have two or more separate problems despite having changed the Aux Battery.
    Maybe the actual act of changing the Aux battery is just bringing forth problems that already were manifesting with the Dash and MFD?

    In other words, we're assuming this is somehow connected to the aux battery or changing of the aux battery when maybe it's not.

    I really don't have an answer here, other than I think you need to start deciding which arm and leg you want to sacrifice to the dealer.

    PS.
    The fact that they didn't keep the vehicle on a charger to keep the computer "alive" while changing the aux battery shouldn't matter.
    I've never read that this is necessary or even recommended. Disconnecting the aux battery to replace it? Shouldn't result in needing it to be on any "charger" life support during the changeover.
     
    #7 The Electric Me, Jan 10, 2016
    Last edited: Jan 10, 2016
  8. uart

    uart Senior Member

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    That part at least is perfectly normal behavior for the Prius. When you turn on the headlights it automatically dims the multifunction (LCD) display, as is appropriate for night time visibility.
     
    #8 uart, Jan 11, 2016
    Last edited: Jan 11, 2016
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    Disconnecting the 12 volt will not cause problems. It will lose your radio presets and clock time, things llike that.

    Before going to a dealership maybe get a digital multimeter, and see what sort of volts the battery has, report back?
     
    #9 Mendel Leisk, Jan 11, 2016
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