Boosting with clarity

Discussion in 'Clarity' started by victor_2019, Jan 30, 2020.

  1. The Gadgeteer

    The Gadgeteer Active Member

    An easy way to avoid concern on any damage (to the electronics or the small Clarity battery) a surge might cause by jumping/boosting someone else’s battery is:
    - start with both cars off
    - connect cables correctly
    - turn on Clarity
    - leave connected for several minutes to charge the batteries
    - turn off Clarity
    - disconnect cables or at least the negative cable
    - test start the cars

    However, my preference is a portable battery booster which avoids the whole issue and has the advantage of being able to jump start myself. The small 12v “starter” batteries in hybrids/PHEVs/EVs don’t need much to run down or charge up.
  2. DaleL

    DaleL Active Member

    Yes the Clarity can be used to boost the battery of another vehicle. Last December, my wife and I were going to take a trip to Ohio to visit our kids. We live in Florida. We had her 2017 CR-V all loaded and ready to go. We got it backed out of the garage, but it didn't start right. Turned it off; tried starting it again. It was a no go. We moved all our stuff, except for a dog pen which wouldn't fit, into my 2018 Clarity. Rather than leave the CR-V in the driveway, I decided to try and jump (boost) its battery. It worked and back into the garage it went.

    The Clarity was just fine on the drive to Ohio and back to Florida. My wife appreciated how much more comfortable and quiet it was versus her CR-V.

    The CR-V battery was just a couple of thousand miles out of warranty. I replaced it myself without any problem once we got home.
  3. Cash Traylor

    Cash Traylor Active Member Subscriber

    Hello everyone! So, I know this thread and topic has been beat like the proverbial dead horse (my past input included). I have something new to add to the thread due to new information. I do not recommend "boosting" other vehicles IF your 12 volt battery is not capable of starting the other car on it's own WITHOUT your Clarity being turned on. So, basically starting very small cars or other BEV/PHEV's. Can you boost with your Clarity - of course, proven numerous times in this thread above. This is about "should you" and what the risks may be if it goes wrong and you damage the DC-DC converter (your "alternator"). I don't care about your 12 volt battery, it is easy to replace and although the charge fuse it part of the positive post (and not cheap) it is nothing compared to the converter. Here is why....

    The DC-DC is rated for 2300 watts and the battery is fused at 175 amps. The converter puts out 14.6 volts, so that means at the fused limit you could briefly pull 2500+ watts. However, the converter in the Clarity is not like other modules in the car that are relatively easy to access for troubleshooting and replacement. In fact, it is "almost" the most difficult to get to item in the vehicle, and would likely not even be touched or serviced by your local dealer. It is INSIDE the Clarity HV battery pack, underneath the HV BCM. It is easier to replace the HV Battery Controller and Balance system (master and slave) than the DC-DC converter. If you have seen the SAE docs this is not new info, I have mentioned it before. What is "new information" is exactly how much surgery is involved to get to this one specific unit!

    So, if you are going to do things that pose a potential surge load to it near it's maximum capacity, and are depending on the fuses or the state of your 12 volt battery to protect it (or it's internal protections) that is fine. However, bear in mind that this unit is about $1900 retail (parts direct, not dealer), and would likely cost that much or more in Honda Dealer Labor to have it replaced out of warranty. This is VERY specialized work, you are unlikely to get service outside of the Honda network or an EV specialty shop if you have to go outside of warranty (due to damage). With it's location I would think it would be part of the extended PHEV power train warranty (8/10 years etc). However, I am not sure it is called out like the battery and traction system is.

    I know this because I have a new pet project that will be put in another thread once I get time to gather all the data and testing. I am reverse engineering the Clarity HV pack. Photo of the DC-DC converter and where it is located is attached. This alone should be enough to caution you on doing anything that may be outside it's design criteria. Unlike most other PHEVs/BEVs it is not easy to get to. You have to spit the HV pack, and then get in close with the "exciting and angry pixies" that live there. Makes changing a blown alternator look like changing a light bulb in a desk lamp.

    Yes, I have an entire HV Pack assembly in my shop right now. Hold the questions, this will go in another thread. Wanted to post this here once I realized how nuts this was and the fact that I highly doubt any dealer tech is going to do this considering all the other issues we have had with dealer support in general.

    This is likely 4+ hours work for a tech with all the docs, not including the removal and re-installation of the HV pack in your car.

    DC-DC In Place.jpg HV BCM over DC-DC.jpg HV Contactor branch.jpg Top Down DC-DC.jpg Overview of location_LI.jpg



    Attached Files:

    Last edited: May 19, 2020
    Bbeardb likes this.
  4. Steven B

    Steven B Active Member

    While most opinions here say having the engine running is not necessary, if it makes you feel better to do so, here are instructions posted by a former forum member:

    The car has a maintenance mode for this purpose [was in response to circulating oil after oil change]. You can force the engine to turn on by doing the following steps. Just for safety, I'd add to set the emergency brake before starting this procedure.

    1) Make sure the car is completely off.
    Note: The rest has to be done within 60 seconds to take effect.
    2) Press the start button without stepping on the brake pedal. Then a second time after a few seconds so that the lights come on around the P on the shift lever.
    3) With the shift lever in P, press the accelerator pedal to the floor twice.
    4) Push the brake pedal and move shift lever to N, release brake pedal. Press the accelerator pedal to the floor twice.
    5) Push the brake pedal and move shift lever to P, release brake pedal. Press the accelerator pedal to the floor twice.
    6) Push the brake pedal and push the ON button to start the car. The display will show maintenance mode and the engine will start after a few seconds.

    When you are done, just push the power button to turn the car off.

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