Potential parasitic battery drain?

Discussion in 'Clarity' started by Arctiic, Aug 9, 2020.

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  1. Anyone else having any issues? I have the 2018 plugin non-touring, and starting from about a week or so back the 12V battery has been dying on me between uses (sometimes, if I just shut it off, it immediately isn't able to start back up). This was severe enough that once — last night — I was actually unable to shift transmission gears for a while even though the car was started and the 12V was still hooked up to an external power supply. With the exception of last night, once it's been started it seems to drive perfectly fine without any issues. I have left the 12V charging overnight on multiple occasions now (and performed a 24-hour conditioning cycle), and I've also tested the alternator and inspected the battery's visual window indicator, all of which appear to be fine. Making the assumption these indicators can be trusted, my next inference would be a parasitic battery drain, but I have no idea how to confirm this. Any ideas or experience with this issue?
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  3. su_A_ve

    su_A_ve Active Member

    Time to visit the dealer - assuming it's still under warranty or you got Honda Care... Otherwise, I'd be buying a new one.

    Most stock 12v that come with a new car never last 4 years. And depending on how long your car was sitting out before you bought it could have gotten discharged and got premature wear.
    Pooky likes this.
  4. I forgot to mention, but this 12V was actually newly replaced under warranty, roughly about a year ago. Or at least, I assume they replaced it with a new one.
  5. How did you test the alternator?

    If you’ve installed any gizmos that are powered by a “always hot” 12V supply, they could be draining the battery.

    I’ve left the car for a month, unplugged, no battery maintainer, and it power up. Voltage was 12.45 prior to firing the ignition switch.

    The big test may come next month, when a return visit to the abandoned car may occur. It will have been sitting in the garage for nearly 6 months, unplugged.
  6. The battery charger I used (this one) includes the function to do so.

    I don't have any mods or aftermarket hardware installed, the only thing I've tweaked would be the HMU but I'm not sure that would impact the electrical system...?
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  8. bpratt

    bpratt Active Member

    The Clarity doesn't actually have an alternator, the 12 volt battery gets charged from the traction battery through an inverter. One common problem for a 12 volt battery not charging is dirty cable connectors. You might try removing each cable from the battery and cleaning the battery terminal and the inside of the cable.
    Daniel M W likes this.
  9. It is actually a DC/DC Converter.
    insightman likes this.
  10. Thanks, that’s interesting to hear!

    Regarding the terminals/cables, I was considering purchasing a set of quick release cables but noticed there’s more going on in the Clarity cables compared to standard ones I’m used to seeing. Are there any that would work for the Clarity?
  11. You could install a battery disconnect switch.

    Potential drawbacks to disconnecting the battery are:
    Remote won’t work to lock/unlock doors.
    Alarm system will be deactivated.
    Computers will reboot.
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  13. leop

    leop Active Member

    The battery cables to battery posts were fairly well corroded when I checked a few months after the purchase of my 2018 Clarity. This Clarity was made on 10/2017 and purchased 2/2018 (central Indiana). After I cleaned the cable to post areas, I had no more of the multi-warning dash messages that are often the result of low 12V battery voltage.

  14. It's not impossible for a one year old battery to suddenly suffer an internal short circuit failure. Don't rule out a defective battery.

    As far as confirming parasitic draw, I believe one can use a sensor that clamps over the cables to measure for current.
  15. craze1cars

    craze1cars Well-Known Member

    Can almost guarantee the battery itself is the problem. Replace. At a minimum have it load tested to rule it out. The window indicator is useless...it only shows the health of one out of 6 cells. If another cell has failed, the battery is junk.
    neal adkins likes this.

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