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Added 12V Accessory battery monitor...

Discussion in 'Gen 3 Prius Accessories and Modifications' started by thordehr, Jun 22, 2014.

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  1. thordehr

    thordehr Member

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    In a previous post, I found that going to the service menu to find the Aux battery voltage is kind of a pain and it doesn't read accurately compared to direct reading from the battery or the 12V outlets.

    I have heard that if the 12V battery is low, it can possibly lead to low fuel economy and weird problems that are hard to track down, unless you know to check the Aux battery.

    I was looking for an easy way to see the voltage every day. This is what I came up on round one:

    [​IMG]

    Worked and was cheap, but didn't match the green of the existing instrumentation and didn't leave me a way to plug in my iPhone charger. (I'm using the one in the armrest for a full time iPod)

    Here was round two:

    [​IMG]

    That worked, the color of the digits at least wasn't red, and it allowed me to plug in the charger. One problem. From the driving position, you can't see the readout for either this solution or the first solution unless you hunch down to look under the bridge:

    [​IMG]

    Here's the final solution:

    [​IMG]

    Voltage display from adafruit placed where the blank was in my car. I had to enlarge the hole to the top and the right slightly to make it fit. I had to remove one of six tangs to make room. This small trim panel would do fine with four. Five is plenty:

    [​IMG]

    Once the hole is the right size it snaps in position with the side tangs on it's case:

    [​IMG]

    I also removed the female portion that the tang went in to give room for the bulk of the device when the panel is back in place:

    [​IMG]

    I used positaps to tap into the ground and +12V leads that go to the 12V outlet. (The car harness had the black wire as +12V and the ground is the striped wire):

    [​IMG]

    Here it is installed:

    [​IMG]

    Here it is from driving position:

    [​IMG]

    It's pretty close to the dash color, is easy to read, and cheap at less than $8.
    Panel Volt Meter - 4.5V to 30VDC ID: 575 - $7.95 : Adafruit Industries, Unique & fun DIY electronics and kits
     
    #1 thordehr, Jun 22, 2014
    bisco likes this.
  2. xliderider

    xliderider Senior Member

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    Does it read 13.x volts when the Prius is in Ready mode?

    SCH-I535
     
    #2 xliderider, Jun 22, 2014
  3. bisco

    bisco cookie crumbler

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    some people are amazing. congrats man, that is very, very ingenious.(y)
     
    #3 bisco, Jun 22, 2014
  4. thordehr

    thordehr Member

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    One start push, no brake pedal to get the first stage accessories going (radio only):

    [​IMG]

    Second push, no brake pedal, to get all accessories going along with dash:

    [​IMG]

    Car in full ready mode:

    [​IMG]
     
    #4 thordehr, Jun 22, 2014
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  5. bisco

    bisco cookie crumbler

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    love it.
     
    #5 bisco, Jun 22, 2014
  6. StarCaller

    StarCaller Senior Member

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    looks good, but isn't it too bright at night?
     
    #6 StarCaller, Jun 22, 2014
  7. Chunker

    Chunker My name is Chunker...I wear a hat

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    Hey cool shift knob! Where did you get it?
     
    #7 Chunker, Jun 22, 2014
  8. thordehr

    thordehr Member

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    Don't know. Hasn't gotten dark yet.
     
    #8 thordehr, Jun 22, 2014
  9. thordehr

    thordehr Member

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    Wish I could take credit for it, but it was another user here on PriusChat. Shift knob replaced with piece of this device:

    In Your Face: Welcome - the best smartphone holders

    [​IMG]

    [​IMG]

    I use it every day as soon as I get in the car.
     
    #9 thordehr, Jun 22, 2014
  10. thordehr

    thordehr Member

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    Yep, it's a little bright at night. Looking at solutions to tint the screen, or put in a switch to turn it off entirely at night if needed. The unit itself is not dimmable.

    OR... for more expense(36.85), an analog gage with a large 270 degree sweep and internally lit....

    ISS 2-1/4 ENGINE VOLTMETER GAUGE from Aircraft Spruce
     
    #10 thordehr, Jun 23, 2014
  11. StarCaller

    StarCaller Senior Member

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    I. ordered already the same as yours from Amazon. guess I'll have to put some tinted foil or something over it.
     
    #11 StarCaller, Jun 23, 2014
  12. thordehr

    thordehr Member

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    If I don't go for the expensive aviation voltmeter option, I'll see about disassembling the unit and putting a couple of layers of blackout window tint between the display and the window.
     
    #12 thordehr, Jun 23, 2014
  13. se-riously

    se-riously Active Member

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    #13 se-riously, Jun 23, 2014
  14. thordehr

    thordehr Member

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    #14 thordehr, Jun 23, 2014
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  15. thordehr

    thordehr Member

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    Yea, but plugged in, you can't see it without hunching down. I like readouts in view. A good easy solution though.
     
    #15 thordehr, Jun 23, 2014
  16. se-riously

    se-riously Active Member

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    Well I did write "compromise". That said, on the PIP you wouldn't have to hunch down much at all because the 12v outlet is actually located dead center between 2 heated seat switches. On your Prius, the 12v outlet is offset to the right, which requires you to hunch down more.

    Another option would be a 12v splitter, which would move the display more to the left.
     
    #16 se-riously, Jun 23, 2014
  17. se-riously

    se-riously Active Member

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    0710141804.jpg
    I ended up purchasing the voltmeter/USB port that I linked to. Here's what it looks like installed. Yes, on the PIP you can see the entire display just by tilting your head to the left just a little bit. The display is blocked in normal head position when driving.
     
    #17 se-riously, Jul 10, 2014
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  18. GregP507

    GregP507 Senior Member

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    I could use a voltage monitor for my aux battery. I've had problems with it going dead, owing to it's small capacity. Since the Prius apparently has no fail-safe way to prevent it happening again, at least I can keep an eye on the voltage if I get forgetful again.
     
    #18 GregP507, Jul 11, 2014
  19. szgabor

    szgabor Active Member

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    This is cool, but 12V "battery" voltage is NOT indicative of your actual batter status, after you turned on car and it is in ready. In ready mode voltage converter drives the 12V bus not the Aux battery. You could tell when the car charges it showing something 13.8-14.6 and when it charged 12.4 or so.

    If you really want to test you need to test open voltage after a few hours stopped but you need at least an hour drive. Better overnight. Even before you open the driver side door which initiates the break cylinder charge. When the car is off there is NO voltage in the 12V port at all. After you turned on see above. It this voltmeter would be attached to the right port of the ODBC port !!! And would be visible from the outside as well, THAT would be something else. (provided that this meter draws small enough to be let permanently connected)

    Possible use is only in AUX mode when only the AUX battery drives the 12 bus but that is again inaccurate because already went through the above and it is not an open circuit measurement (bunch of things loads it). I just can not see how this would help that much if at all to detect aging 12V battery (maybe better than nothing)
     
    #19 szgabor, Jul 11, 2014
  20. JC91006

    JC91006 Senior Member

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    These are good examples of things to add that other's don't have. These digital screens are probably not rated to be on every time the car is on, so you would need to keep a few on hand to replace when they go out. Or risk having a broken display in your car.
     
    #20 JC91006, Jul 11, 2014
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