Could be a bad 12V battery...

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by AtkinsonCycle, Mar 10, 2018.

  1. AtkinsonCycle

    AtkinsonCycle Junior Member

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    Hello all. Thanks for the excellent sharing of experience - that's what this is all about. Here is what I have found. I was on my way to Pep Boys to purchase their offering of a replacement battery - a Bosch Platinum Series with a great warranty and a great price with 25% off until April 1rst. A long time ago, I worked in an automotive shop and had a call in to a friend detailing my issues. As I was leaving to go to Pep Boys, he stopped by with a battery load tester. We found 12.59 volts and it passed a 250 CCA load test.

    I had a call in to Pep Boys, and I felt obligated to go and share what I had found even though I didn't need the battery. They had the Bosch in stock and Brianna (the girl I spoke with) had it on a trickle charger. It showed 12.61 volts and had over 300 CCA's.

    Bosch Premium Performance Battery Group, Size 51 | 647478 | Pep Boys

    I told her I had checked the battery already, but offered to let her test it as well. She did and it confirmed the first check: 12.61 volts and 188 CCA's. It's not the greatest, but should be enough to boot the control units on start up. I will connect my battery minder charger and see if I can get a little more amperes into it (ultimately, out of it). I thought about purchasing the battery anyway and having it just in case. It has a free 4 year replacement warranty and after 4 years is pro-rated. If I were to buy it, it would almost guarantee I won't have any more problems... :) But, I can't see spending $150 on a battery to replace one that passed the load test. I don't want to throw money at a problem or guess - it passed the test, so the problem is elsewhere.

    I think I may have a connection issue somewhere on the car. It could be a relay, but the display screen was dead when I opened the door (it didn't show the car with a door open on entry). I would think the module that displays the car and door status would be powered all the time - so when you open the trunk or any door, it shows the car on the dash and which door is open. When my problem occurred, I had no display. When it did start to display, the car image was dim and fluttered on and off. With the display dead, I did try to insert and turn the key to engage ready mode. I got nothing. After about five minutes while I was checking the obvious, I reopened the door and saw the bright image of the car with the door open. I tried the key again and the car went into ready mode with no issues.

    Today, I had no issues with the car. I guess this will be an ongoing issue until it rears up again. I did find a thread here where someone experienced similar symptoms, but I did not bookmark it. In the thread, someone had suggested that thermal expansion and contraction may be causing a connection to open and close randomly (with temperature). I haven't looked for schematics yet, but generally, the schematic is only so good - an 'as installed' diagram is great if the schematic does not tell you where connections are and routings go. In the past, I have seen standard electrical schematics accompanied by a page that shows where connections are in the car (Ford). I image Toyota would do this as well and maybe even detail the 12V side of things separate from the 144V side.

    If anyone has experience with a problem similar to this, please share...
     
  2. davids45

    davids45 Member

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    G'day AtkinsonCycle,
    I'd suspect you don't have a problem with "car" (the traditional bits of it like the easily tested 12V battery), but with one of its computers/processors (the new fangled 'invisible' stuff) that could have an intermittent open-circuit or short or condensation on a cold morning.

    Unfortunately, maybe only when whatever it is totally fails, will you or a knowledgeable service technician become 'the wiser', and probably (you) the poorer.

    Autogenous healing could kick in if you're really lucky?

    David S.
     
  3. Andyprius1

    Andyprius1 Senior Member

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    Read this whole string, when the car is running, in ready, does your multimeter read 14.5 volts ? at the battery or access terminals?
     
  4. AtkinsonCycle

    AtkinsonCycle Junior Member

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    Thanks for reading this. I have to check to see what voltage is present after the ready mode is engaged. I have done quite a bit of reading. It seems that a bad inverter pump can cause the DC - DC converter to shut off and not charge the 12V battery. I will check the voltage present once ready mode is engaged and also check to see I have flow in the inverter reservoir once ready is engaged. My guess is the converter is working. I say that because I checked the battery voltage two days ago and it showed 12.38 VDC. Today, it showed 12.61 VDC at the time of the load test. Nonetheless, it is a guess. I will be checking it and reporting back.
     
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  5. AtkinsonCycle

    AtkinsonCycle Junior Member

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  6. hayden55

    hayden55 Member

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    I think there is a misconception between the voltage at which the charging system charges at and a stationary battery. Typically a 12v nominal battery when fully charged will sit at 12.84V and is at 100% depth of discharge at 11.7V. Now most batteries that come in cars these days are starting batteries which means they don't have as many usable life cycles as a deep cycle when drained past 60% repeatedly. Odyssey is actually a good example as I think their entire line is deep cycle batteries. They recommend that their batteries only be taken to 80% dod maximum. 80% depth of discharge on their chart is ~11.84 V. Also all of these values are at optimal temp (77F).
     
  7. Sam Spade

    Sam Spade Senior Member

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    Good information.
    But how does it relate to the discussion at hand ??
     
  8. hayden55

    hayden55 Member

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    Now you can interpolate the value of your battery between the two values given and somewhat determine usable life left in the battery.
     
  9. Sam Spade

    Sam Spade Senior Member

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    A chart would be much better.
    Links have been provided in the past.

    (The system won't accept .XLS uploads.)
     
  10. AtkinsonCycle

    AtkinsonCycle Junior Member

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    Hello. 14.57VDC at the battery when ready is engaged. It still has been happening occasionally (not every day), but only happens once then it's done for the day. The brake booster pump is seeing less than 12 VDC when I open the door, so it makes some strange sounds because it's not seeing 12 V. I wish I had a schematic or as installed wiring diagram to know where connections are on the 12 V side. When this happens, I have no lights on the dash, no display on the LCD, no vehicle graphic (showing the car with the door open), and the brake booster motor runs slow. Any ideas on where to look for connections? Thanks!
     
  11. ChapmanF

    ChapmanF Senior Member

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    I'd suggest going straight to the wiring diagram at techinfo.toyota.com. The power distribution routing is convoluted enough in these cars that nobody's thousand words in a PC post would tell you as much as looking at the picture yourself.

    When you say "when I open the door", I assume the car is OFF at that time, right? So your measurement of battery voltage when READY doesn't apply then. Do you have any measurement from a meter at the battery, at the same time as you open the door and < 12 V reaches the pump?

    -Chap
     
  12. AtkinsonCycle

    AtkinsonCycle Junior Member

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    So, I have seen 12.38 to 12.61 VDC at the battery after at least 6 hours of rest. I can hear the brake booster pump run slow when the problem occurs. Thanks!
     
  13. Sam Spade

    Sam Spade Senior Member

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    YOu don't need any kind of wiring diagram to check the main battery connections.

    Two of them (at least) are ON the battery posts; remove, clean and re-tighten.
    Then find the OTHER ENDS of those main cables and clean and tighten there too.

    And ......"wiring diagrams" usually just show how things are connected electrically and give no clue as to how the wires are actually physically routed.
     
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  14. ChapmanF

    ChapmanF Senior Member

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    Haven't looked at the Toyota EWDs much, I take it? That's kind of what the "location and routing" sections are for.

    AtkinsonCycle was not looking necessarily just for main battery connections, but for the possible sources of voltage drop between there and the brake pump, which was reporting undervoltage. There are several junctions, connections, and fuses on that path, which you could trace out with a bunch of harness untaping and circuit probing, I guess, or by glancing at the ... well, never mind.

    -Chap
     
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  15. Sam Spade

    Sam Spade Senior Member

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    But what does the voltage read when the problem occurs ??

    Check at the actual battery posts and at the cable ends connected there (yes, those readings might be different, indicating a bad connection).
     
  16. Sam Spade

    Sam Spade Senior Member

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    BUT......he needs to verify the power SOURCE before digging into individual connectors and wire runs.
    I think it is highly likely that the brake pump is not the ONLY thing that is seeing low voltage.

    You are right that I have little experience with Toyota's shop manuals.
     
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