Is it OK to use my Clarity to jump start my Prius?

Discussion in 'Clarity' started by ozy, Jan 12, 2019.

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  1. ozy

    ozy Active Member

    My Prius is parked in the same garage as my Clarity. For some reason the Prius has battery problems and needs to be jumped quite often. I don't think that it's simply an issue of changing the battery because the battery is 3 years old and yet the car has required 3 jumps within the last 6 months. I used to jump it with my previous car but now have the Clarity instead. Is there anything special I need to know regarding using the Clarity to jump start the Prius?
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  3. ernda

    ernda New Member

    I've owned Priuses and recall that jumpstarting them is akin to allowing the car to "reboot". You're not trying to turnover the engine, so the battery on the Clarity should be fine. If you're doing this a lot you may want to invest one of the small lithium ion power pack jumpstarters. Much more convenient than running cables between two cars and you just keep it in the car for a quick jumpstart anywhere.
    228ra likes this.
  4. Walt R

    Walt R Active Member

    Not to contradict you, but I found that the (12V) battery life on my 2008 Prius is about 4 years. Plus, conventional car batteries have much shorter lives once they have been fully drained once and jumped back to life. So, I would go ahead and replace that battery. (Though the Prius does take a smaller, lightweight battery than the standard 12V. I recall around $300 for mine.)

    I am also hoping that the 12V system is fairly standard on the Clarity. I have a 1200W inverter I can wire to the remote 12V terminals in my Prius in case of power outage - the Prius will run the engine about 25% of the time to supply that power as opposed to 100% idle on a conventional car. I am hoping I could wire it up to my Clarity 12V system and get 12 hours of power before even running the engine.
  5. MNSteve

    MNSteve Well-Known Member

    My understanding is that the 12 volt system in the Clarity is charged by a DC-to-DC system that moves power from the traction battery to the 12 volt system. I do not know what the capacity is of this unit, but for normal operation it would not need to be very robust, as it is just replacing power taken from the 12 volt battery for devices on the 12 volt system. Trying to pull constant significant power from the 12 volt battery may have results that are not what you expect. It is also my understanding that this DC-to-DC function only operates when the car is "on", including accessory mode.

    If I planned to use this as an emergency source of power, I would test it before the emergency.
  6. Sandroad

    Sandroad Well-Known Member

    Using the Clarity to jump start another vehicle (or not) will be in the Owner's Manual. However, given the problems you have with the Prius and the potential for that to occur anywhere, I strongly recommend you get a NOCO Genius booster for your Prius and use that. It's much easier than hooking up jumper cables to another car and can be carried with you in the Prius. I have a NOCO in both of my vehicles for peace of mind and they work great (including emergency USB charging of phones). They come in many different capacities and for the Clarity you need only the smallest.

    And I concur with the post above that it's time for new 12V battery if it's 3 years old and giving you trouble.
    02Duck likes this.
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  8. insightman

    insightman Well-Known Member Subscriber

    This poster used his Clarity with an inverter to power devices in his home after a hurricane. He later said that the Clarity PHEV has to be On to get the DC-to-DC converter to recharge the 12v battery.
    ClarityDoc likes this.
  9. Walt R

    Walt R Active Member

    Thanks for the link to the other thread, @insightman . It appears that a Clarity with a 1200W inverter hooked to the battery will operate as I expect, which is to cycle the ICE on and off to maintain the average output. Having to put the car in On is what I expect, since the Prius also would not run the ICE to replenish the small high-voltage battery unless fully On. Hopefully the Clarity will also use the high-voltage battery for a while before recharging with the ICE.

    The only additional wrinkle may be the car shutting itself off. The Honda has so many auto-off timeouts that even with the key in it, if it doesn't move for an hour it might turn off. But, I intend to only do this while I am awake and swap out single loads at a time, so even that wouldn't be a big deal. And yes, doing a dry run before the power is actually out (and it might be dark) is almost required.
  10. MNSteve

    MNSteve Well-Known Member

    Apologies for posting a non-Clarity story, but this one teaches a lesson.

    Years ago there was a high-rise residential building in Chicago that had an emergency generator. They religiously tested it every month. Then one day there was an actual power failure. As expected, the generator started and powered the emergency circuits ... for about five minutes, at which point it shut down. Turns out that it was in a tiny room that had ventilation louvers to provide the air needed to run the engine. These louvers were electrically powered and were not on the emergency circuit, so when the power actually went out, they closed. The seal was so effective that the generator could not run.
  11. Sandroad

    Sandroad Well-Known Member

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  13. Walt R

    Walt R Active Member

    Another off-topic story along the lines of @MNSteve 's post. A few years ago I was on a project that renovated a building to be a dispatch center, so it included a generator. I insisted on a live test of the generator circuit and UPSes - so interrupt the power at the mains and let the normal monitoring systems do their thing. We had put about $500,000 worth of new server equipment in the IT room. We did the generator test twice - once with all the computer equipment safely off, and then a true live test with all the computer equipment in the building up and operating. I was fairly nervous that we would fry some expensive servers due to miswiring or voltage surges, since I was the one that insisted on the test, but luckily nothing went wrong. I was able to justify it to myself that if anything went wrong, it would have gone wrong the first time the generator was really used, and then would be worse because it would be unplanned.
    MNSteve likes this.

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