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2013 Plug-in 12V Battery Dead when not driven everyday

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by powerplay, Jun 9, 2023.

  1. powerplay

    powerplay Junior Member

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    2013 Prius
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    I have checked the DC-DC Converter and it is outputting 14.3V when the Ready light is on. If the car isn't driven for a few days the battery is drawn down to about 5V. The battery is brand new about 3 weeks ago and I have recharged it with an AGM charger when this happens. According to my DC Clamp meter on the negative cable, the car is completely off, there is about a 2amp draw on the battery. I have pulled the cable from the fuse box for the DC-DC converter and it drops to about 0.4amps. Plugg it back in and it goes right back up. This is with a fully charged battery. Both by an external battery charger and the DC-DC converter with the engine running and monitoring the current draw of about 0.6amps. I need to fix this as the car is driven to work during the week. Is the DC-DC converter a part of the inverter? Can it be replaced by it's self?

    TIA for all comments and help.
     
    #1 powerplay, Jun 9, 2023
  2. bisco

    bisco cookie crumbler

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    any trouble lights?
     
    #2 bisco, Jun 9, 2023
  3. powerplay

    powerplay Junior Member

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    No trouble lights. It is normal in all regards except something is drawing about 1.5amps via the DC-DC converter. If you unplug the converter line in the fuse box, it stops of course. I don't know if it is actually a problem with the converter or something else that is connected to the converter, which I guess could be anything that runs on 12v.
    I also checked for any ODBII codes and there are none.
    A little more information for the forum members. I do not know if this is a normal condition, but there is a 1.5amp draw on the 12V battery sitting still in the garage. Since this is a plug-in, I plug it into my charger and checked the battery voltage and amperage draw. Unplugged it was 12.66V and 1.5amps. Plugged init was 13.4V and 4.8amps. So the 12V battery does in fact get charged when the traction battery is being charged. However, once the traction battery is charged I will have to see if it still keeps the 12V battery charged and offsets the 1.5V draw. I will update this post with that information.
     
    #3 powerplay, Jun 10, 2023
    Last edited: Jun 10, 2023
  4. Paladain55

    Paladain55 Active Member

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    2 amps is pretty huge. I just did a battery draw diagnosis on my 2001 Sequoia. My draw was 0.27A. More or less after pulling fuses I found the ECU and security pull the majority of the power, and my battery is really just deader than a door nail.
    Since you have a clamp start pulling individual fuses and relays and see how it effects your draw. Some things we've seen over the years: the cd player in the 05-09 mustangs will fail and continuously run while the car is off, c5 corvettes power seats fail somehow and seats draw power when off, heated seats here in there can draw power, the ABS pumps in old Suburbans and Tahoes can fail and run when off etc.. It can be a lot of anything.
     
    #4 Paladain55, Jun 10, 2023
  5. powerplay

    powerplay Junior Member

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    Thanks and that will be my next step once I determine what happens to the 12V battery after the Traction battery is fully charged.

    When the traction battery is fully charged and the current flow stops from the wall-mounted external charger, so does the current flow to the 12V battery.

    So next task is to monitor the current flow from the 12V battery (1.5amps) and pull fuses from the box under the hood. We will see if that has any effect.
     
    #5 powerplay, Jun 10, 2023
    Last edited: Jun 10, 2023
  6. BiomedO1

    BiomedO1 Senior Member

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    On my car, 12 VDC charging stops when traction battery is full. Yours is probably setup the same way.

    RE. current flow; you know there are about 3 types of sleep cycles for your car. Each sleep cycle draws less power. Once your FOB is in range, your car is drawing the most power - while OFF. It's waking up the CPUs and prepping the car for operations.
    Most current draw issues I find are either fused relays in the close position or after-market equipment. I would rarely run into a wire where the insulation was either chewed or rubbed away, causing an intermittent short. This is usually caused by vermin or a poor accident repair.
     
    #6 BiomedO1, Jun 10, 2023
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  7. powerplay

    powerplay Junior Member

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    Thank you for your input. That is a very good point about the "sleep" states. I went and checked this morning without the FOB in my pocket and the reading was the same, 1.5amps. The battery was still at 12.67V, so it didn't discharge too much overnight.
     
    #7 powerplay, Jun 11, 2023
  8. BiomedO1

    BiomedO1 Senior Member

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    Most cars I've ever worked on; not Prius - any draw over 0.05A was considered excessive. That's using a meter in series; not using a clamp-on. You may want to check the specifications on your clamp-on meter to see if it's sensitive enough.
     
    #8 BiomedO1, Jun 11, 2023
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  9. ASRDogman

    ASRDogman Senior Member

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    Perhaps you have a defective battery, it happens.
    You could disconnect the battery at the fuse box, then check it in a day or two.
    If the votage goes down you know the battery is defective.

    You can start removing fuses until the draw stops, then you'll know the circuit the draw is on.

     
    #9 ASRDogman, Jun 11, 2023
  10. powerplay

    powerplay Junior Member

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    You may very well be correct. I don't have a meter ,at the moment, that will check DC amperage. Hence the use of my Fluke clamp on. It has been very consistent with the measurements I have taken, but I may need to look at finding a good DC amperage meter.

    Thank you.
     
    #10 powerplay, Jun 11, 2023
  11. nicoj36

    nicoj36 Active Member

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    Sometimes brand-new batteries come out as defective. I would do a load-test on that. Also, check your dome lights in the front, back-seat, and trunk light if any of them is left on. And other things you have plugged into the cigarette socket.


    I would also give it a reset.
     
    #11 nicoj36, Jun 13, 2023
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