How do I check the 12 volt battery on my 2017 Prius Plug -In PHEV

Discussion in 'Prime Technical Discussion' started by noddyDublin, Feb 12, 2020.

  1. noddyDublin

    noddyDublin Junior Member

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    How do I check the 12 volt battery on my 2017 Prius Plug -In PHEV [16000 miles European model]?.
    It shows 11.8 volts on my Fluke multimeter.How do I get into the built-in diagnosis in the multi display?
    When I originally charged the traction battery it showed a range of 40 miles, now it only shows 35 miles.
     
  2. Rob43

    Rob43 Senior Member

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    11.8 volts on your Fluke is definitely low.

    As a baseline, I want you to try this testing method to check your 12v battery:

    1) Park your Prime with roughly a Depleted traction battery.
    2) Then pop your hood so you don't wake up the car / computer with your key fob later.
    3) Plug your EVSE in & fully charge up your Prime.
    4) Unplug EVSE from car & wait ~1 hour.
    5) Lift hood (no key fob) & test 12v battery with your Fluke meter, this should give you your best result.

    No matter what, I'd tell you to put some type of low amperage charger or trickle charger on it until you get a full charge.

    Here's what I did to help my 12v battery stay a little bit healthier, pics below.


    Rob43

    thumbnail_(29)_-_Edited_(2) - Edited.png

    Screenshot 2019-05-07 at 1.12.16 AM.png
     
  3. Elektroingenieur

    Elektroingenieur Senior Member

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    As described in my November 2017 posting, the Repair Manual (more info) gives a basic procedure for testing the auxiliary (12 volt) battery; you’d use the version from toyota-tech.eu, of course. That posting also describes the equipment used by Toyota dealers in the U.S. for more thorough battery tests.
    As @Rob43 kindly notes, that reading is low. Was it measured with the car turned off? Are there any 12-volt accessories connected to the car, either permanently or at the power outlets?
    See my February 2017 posting, but you may be disappointed: that mode is meant for troubleshooting the audio and navigation system, and it’s not a general diagnostic or indicating system for the car.
     
  4. Chazman62

    Chazman62 Member

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    I've seen different multimeters showing different readings on battery. I say confirm the VDC reading again with another multimeter if avail.
    Also, perform a load test after fully charging the battery instead of just relying on the terminal/surface voltage reading.
    And, yes, attaching a trickle charger definitely prolongs the life of the battery. I had a (factory installed) battery that lasted 9 years in one of my previous cars that I bought new from a dealership by trickle charging it whenever not driving daily. I sold that car with the same battery after owning for 9 years. But some batteries lasted only 3 years even trickle charged.
    If your battery already has started becoming weak/sulfated, usually it's too late to revive fully.
    Sulfation in the battery is like a cancer in your body.
    Once it has started to spread, consider it done.
    It's best to prevent the sulfation when the battery is new by (1) avoiding deep discharge (2) and hooking up to a trickle charger.
     
    Rob43 likes this.
  5. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    (oops. duplicate post)
     
  6. bisco

    bisco cookie crumbler

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    17’s had a lot of bad batteries
     
  7. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    I have a charger that can provide either 10A or 2A, and is intelligent about the charging protocol, like stopping when full. Is 2A considered trickle charging for an automotive battery? Actually this question is for my wife's Honda Pilot, which isn't getting much use these days.
     
  8. Rob43

    Rob43 Senior Member

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    A "Smart" 2 amp (or less) car battery charger would be considered a trickle charger.


    Rob43
     
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