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Peculiar Battery Issue

Discussion in 'Gen 3 Prius Technical Discussion' started by dmaster3, Jan 30, 2018.

  1. dmaster3

    dmaster3 New Member

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    Hey everyone,

    I have a 2015 Prius 3 which has a brethalyzer installed in it. The unit is a constant drain on my battery when it's cold out but that's never been a problem until now. I woke up the other morning and could not start my car. After a call to the brethalyzer's service provider I found out that the unit needs 12 volts to start. I've ordered a battery charger
    and I'm curious if I should hook up to the front fuse box or the rear battery. Opening the hatch is no problem because I found the manual release. What do you think would be the quickest but best charging option for the vehicle? I'm parked in a lot behind my building so I'll be running a long extension cord out to the car. I'd like to minimize my time being out there.

    Thanks for all of your help!
     
    #1 dmaster3, Jan 30, 2018
  2. padroo

    padroo Senior Member

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    Either will work but I always used the one in the front fuse box, it was put there for that purpose.
     
    #2 padroo, Jan 30, 2018
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  3. dmaster3

    dmaster3 New Member

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    Is there a limit as to how many amps I should run through that connection? The charger I bought can deliver up to 15 amps but I know the battery in the back doesn't like over 4 I believe.
     
    #3 dmaster3, Jan 30, 2018
  4. Prodigyplace

    Prodigyplace Senior Member

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    @Mendel Leisk does a lot of battery charging. I believe a charger specifically for AGM batteries is preferred. I seem to remember it likes 4 amps, preferably less (3?).
     
    #4 Prodigyplace, Jan 30, 2018
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  5. padroo

    padroo Senior Member

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    Most people don't know what an AGM battery is but they are becoming more common and like Mendel says they like a slow charge not over 4 amps. All batteries are better charged long and slow because heat is the enemy of any battery. It's one thing to give a battery a boost or jump start and another to charge it on high amps and long.
     
    #5 padroo, Jan 30, 2018
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm using a CTEK 4.3, 4.3 amps like the name.
     
    #6 Mendel Leisk, Jan 30, 2018
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  7. dmaster3

    dmaster3 New Member

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    Alrighty, I’ll keep it under 4.2 and for less than 10 hours. The last thing is that when I tried to jump the vehicle the cables were reversed on the working car. They were left my car on the positive terminal for less than a minute until I realized what had happened
     
    #7 dmaster3, Jan 30, 2018
  8. dmaster3

    dmaster3 New Member

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    The battery in the back says no more than 4.2A for more than 10 hours so I'll stick with that. I should mention that when I tried to jump the car originally the polarity was reversed on the car doing the jumping. I removed the cables in less than a minute so hopefully nothing is fried when I get the battery charged enough to power the brethalyzer to start the vehicle.
     
    #8 dmaster3, Jan 30, 2018
  9. padroo

    padroo Senior Member

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    If charging the battery doesn't fix it you may need a volt meter to do some troubleshooting.
     
    #9 padroo, Jan 30, 2018
  10. Prodigyplace

    Prodigyplace Senior Member

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    If the cables were reversed you may have blown the fuse in the positive battery connection, or fries the inverter that charges the 12 volt battery.
     
    #10 Prodigyplace, Jan 30, 2018
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  11. Mirza Murtaza

    Mirza Murtaza Junior Member

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    Hi
    Is 12v AGM battery necessary for Prius or any other sealed maintenance free battery can be used.
     
    #11 Mirza Murtaza, Jan 30, 2018
  12. Prodigyplace

    Prodigyplace Senior Member

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    For safety it should be a 12 volt AGM battery that accepts the external vent port to vent gasses away from the passenger compartment.
     
    #12 Prodigyplace, Jan 30, 2018
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  13. dmaster3

    dmaster3 New Member

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    Which fuse should I check?
     
    #13 dmaster3, Jan 30, 2018
  14. Mendel Leisk

    Mendel Leisk Senior Member

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    I would only start looking for blown fuse if there's abnormal behaviour. If the car behaves normally then you should be fine I think, no fuse blown, knock-on-wood.

    I'm kind of sceptical that the breathalizer unit ran the battery down, at least if it was installed correctly. This would be a complete design fail on the part of the manufacturer I think. Again, maybe it's not connected properly, or malfunctioning??

    And yeah: check the voltage of your existing battery, at least for starters. Better assessment can done with electronic load testers. Battery retailers often have these, and will test for free. You can also get DIY level testers, Solar BA5 for one.
     
    #14 Mendel Leisk, Jan 30, 2018
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  15. dmaster3

    dmaster3 New Member

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    So I charged the battery enough to activate the breathalyzer and then started the car. It powered on and then after 3 seconds went dead. It also did not display the “0” under mph when started. I think my only option is to get it towed to Toyota.
     
    #15 dmaster3, Jan 30, 2018
  16. padroo

    padroo Senior Member

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    Sometimes that is the quickest way especially if you need the car.
     
    #16 padroo, Jan 30, 2018
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