2016 Toyota Axio Hybrid – Dead HV Battery (P3000-388) – How to Recharge?

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Juaxio, Mar 13, 2025.

  1. Juaxio

    Juaxio New Member

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    Hey everyone,

    I have a 2016 Toyota Axio Hybrid, and the HV battery got completely drained because the car was left in neutral with the AC on. Now, the battery is sitting at around 60V, and the car won’t start. I scanned it and got the trouble code P3000-388.

    I’m an automotive technician, so I have some experience working on cars. From all my checks, the battery is just too low to start the engine. I tried to force start it using Techstream, and while it did turn the engine a bit, it wasn’t enough to fully start it.

    The problem is that I live in an area where there are no shops or mechanics that service hybrid vehicles, so I need to figure out how to recharge the HV battery myself.

    Does anyone have experience with reviving a completely dead hybrid battery? What’s the safest and most effective method to get it back up to a usable voltage? Any advice would be greatly appreciated!

    Thanks in advance.
     
    #1 Juaxio, Mar 13, 2025
  2. Tombukt2

    Tombukt2 Senior Member

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    If you do a search right here in this forum you will see there is a charger that everybody's building for $90 $88 something You're going to need basically a 300 volt DC supply at about 2.4 amps that should bring you up to $211 220 volts in four or five hours maybe a tad longer You want to run the charger with a voltmeter or something connected in series and when the battery charges to the point where there's no change in like 5 minutes on the display that's about the time to disconnect your charger and it shouldn't be heating or anything at that point and then that should be at a point where they'll be plenty of voltage to start your car how you're going to do it out in the wild MacGyvering it I'm not sure what to tell you I couldn't give you a parts list of what you need to round up but those posts will they'll tell you exactly what they've used other than that an owner that's near you might have one of several manufactured hybrid chargers that they might be willing to lend you or something I have no idea It does happen but I have no idea where you are.
     
    #2 Tombukt2, Mar 14, 2025
  3. MAX2

    MAX2 Senior Member

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    If you measured the voltage correctly and the high-voltage battery only has 60V, then unfortunately, it can be thrown into the trash. Even after charging the battery, it will not work.
     
    #3 MAX2, Mar 14, 2025
  4. Juaxio

    Juaxio New Member

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    Ok so i got the car running, and the battery is charged and to my surprise, it actually worked. (Disclaimer: DO NOT TRY THIS unless you know what you’re doing – high voltage can be dangerous lol!)
    1. Removed the HV battery from the car and took out all the modules.
    2. Connected them in parallel (again, don’t do this unless you're sure about the risks).
    3. Used a 12V 5A charger to charge them up, monitoring with a multimeter. Let each module reach about 8V before stopping.
    4. Disconnected the charger and let the modules self-balance for a few hours.
    5. Reconnected everything in series and checked the voltage—got 160V at the pack!
    6. Put it back in the car, and boom—I’m back on the road.
    I honestly didn’t expect this to work, but here we are. Has anyone else tried something similar? How long do you think this will last?
     
    #4 Juaxio, Mar 14, 2025
    bisco likes this.
  5. Tombukt2

    Tombukt2 Senior Member

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    Yes that's like hobby charging the modules I should be no problem however you get them up to around 8 volts apiece or 7 point whatever it is and then let them stabilize like batteries do and then rack them all back up which gives you a chance to clean bus bars and all of that sort of thing that's all good things That's what you should be doing cleaning all that stuff up so seems like a win-win
     
    #5 Tombukt2, Mar 15, 2025
  6. bisco

    bisco cookie crumbler

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    Well done!
     
    #6 bisco, Mar 15, 2025
  7. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Now that you have got it going, it should maintain itself fine. So it'll last until the next time somebody leaves it in neutral.

    ...or are you asking about overall battery lifetime? The smaller pack in the Aqua/Prius c seems to last about 10 years in warmer climates. This event may have knocked some extra life out of it, but not necessarily.
     
    #7 Leadfoot J. McCoalroller, Mar 16, 2025
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