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Prius 12V battery charging at 14.9V/10A???

Discussion in 'Prius v Main Forum' started by TWrecks99, Dec 8, 2020.

  1. bisco

    bisco cookie crumbler

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    it sounds to me like you got a new battery that had been sitting for some time, and need a charge before installation, which most places never do.

    i would either buy a smart charger, insist the place you purchased from put it on a charger, or call around to auto parts stores to see if anyone will give you a free charge.

    a new battery should be reading close to 13v after a full charge and sitting overnight.

    then the charge voltage from the car would be interesting to know.
     
    Air_Boss likes this.
  2. TWrecks99

    TWrecks99 New Member

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    Whoever put the interior fuse box there should be shot... I took a look during lunch but its almost impossible for me get to with doing injury to myself - have to be upside down in the foot well with my mid-back on the door sill. I'll try a small stool for support and see if that helps. I didn't see any sign of a remote start module... usually they don't hide them any harder than they have too.

    I did turn off the smart keys, turns out you can do it from the MFD setup menu. That drops the off drain about 50mA. Readings have been pretty consistent, I don't think this is a ghost. Also the amount the battery drops overnight is concerning.

    Tim
     
  3. Air_Boss

    Air_Boss Senior Member

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    Undoubtedly for ease of assembly, and figuring nobody has a good reason to be there.

    So, it's a feature, a deterrent, not a bug... That's their story, and they're sticking with it.
     
  4. rjparker

    rjparker Tu Humilde Sirviente

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    As promised, we have a result.

    1. Measured 21 ma steady state current. Varied from 20.3 ma - 25 ma. It was 20.3 about 95% of the time.

    2. Opening hatch or a door would draw 1750 ma dropping to 21 ma within 75 seconds after closing the door.

    I did not break the 12v current path to insert the ammeter, so no major sleep delays occurred. I used a $400 meter and then a free Harbor Freight meter. The results were identical.

    Process to insert ammeter withou opening battery circuit:
    Added a jumper from the neg terminal to a grounded hold down bolt. This provided an alternate negative current path. Then disconnected the neg battery terminal at its adjacent chassis ground bolt. This allowed me to hook a ma meter in series to the disconnected cable end and back to chassis. Then removed the first jumper and all the current was flowing through the meter without actually opening the circuit. After sequentially observing the current using two different meters, I connected the first jumper to carry the current and reattached the normal gnd cable. No computer startups.
     
    #24 rjparker, Dec 11, 2020
    Last edited: Dec 11, 2020
  5. ChapmanF

    ChapmanF Senior Member

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    Would it be fewer steps to just have the ammeter in series with the added jumper, disconnect the original ground to get ammeter readings, then put it back when done?
     
  6. TWrecks99

    TWrecks99 New Member

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    If the computer does get power cycled, are there any funky unlocking steps needed? Or just the radio memories, phone pairing and emissions sensors get reset?
     
  7. rjparker

    rjparker Tu Humilde Sirviente

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    No user setups are lost and no unlocking steps. it just takes longer to make valid parasitic measurements.

    As far as the wiring goes it only took a couple of minutes. I did run the wires out of the hatch so that I could close it with the meter outside. I swapped in different meters and took a few other measurements. For example the homelink autodim rearview mirror takes 6 ma.
     
  8. TWrecks99

    TWrecks99 New Member

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    RJ, thanks for all the help.

    The clamp on meter seems to be thrown off when very near the battery even when properly zeroed, I wonder if the large quantity of metal is throwing it off. Another trick to get a better reading on low current from those meters is to loop the wire around the jaw multiple times then divide the reading by the number of turns (even a pass straight thru counts as 1 loop, its just a very big one). But stray fields and ferrous metals can still mess it up. Laying on the chassis metal seemed less problematic.

    I liked your idea of the jumper to the chassis so much I made up cable with spade lug on one end and a banana jack in the other and left it in there under the head of the left hold-down bolt. I did mess up once and the dome light came on with no jumper and the meter in 300ma range popping the fuse.

    After the car settles down (takes some time, it seems like longer and more current with smart key enabled) I was getting the following using the shunt meter in 300mA range:

    40mA +-5mA w/ smart key feature off
    50mA +-5mA w/ smart key feature on

    That includes the remote start module. At one point it seemed like having the interior lights on auto (even when not on) was having impact but I can't reproduce it.

    With the smart key enabled after locking it was drawing over an 1A for couple minutes then 0.28A for while (10min?) before settling down. This was with all keys enclosed in metal. When the current dropped to 50mA, bringing the unshielded key near the trunk didn't seem to change anything, but by the front door did. I also wonder if wakes up for any Toyota smart key? Given how close my keys are stored to the car it makes sense to just leave that feature off at least until I drive the car more regularly again.

    It's Sunday, I haven't charged the battery since Friday when it was 12.8V, it's still 12.45V. I've had the card in standby mode a couple times for a total of 10min or so as well, that draws almost 10A.

    So while the 14.9V charging still seems strange, barring an intermittent like a sticking relay I don't think I have a drain issue. 50mA should last 16 days on a full charge or 8 on half with a good battery... I will try to chase down the remote start module still, once winter is over I don't need it.

    I bought a 10W solar panel and ODB cord anyway, we'll see how that works.

    Tim
     

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  9. rjparker

    rjparker Tu Humilde Sirviente

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    Sounds like you have it under control. Remote start is probably drawing 30 ma since it has to be on 24x7 to work. Fob too close may have been the root cause of the last battery's early demise.

    I did not remember the option to turn off smart key. My 21 ma may go down to 11 ma when needed. Looks like there are built in power savings strategies but they take 14 days to totally disable. See pic.

    Be sure to let your service advisor know, you may want to be on his good side sometime in the future. Tell him you rev'd it up and everything just fell into place.
    E7139D6E-CF25-46E6-B807-A5F08DA5EF1C.jpeg
     
    #29 rjparker, Dec 13, 2020
    Last edited: Dec 14, 2020
  10. Travis Decker

    Travis Decker Active Member

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    Have you checked the battery connections on the battery that they installed and made sure that they are clean and tight?
     
  11. Travis Decker

    Travis Decker Active Member

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    And the other end of the negative cable
     
  12. sam spade 2

    sam spade 2 Senior Member

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    So....now I think you need to consider that there really IS a problem.....but it's not what you have been chasing.
    It is likely, I think, that there is something that is drawing excessive current from the 12 V system while the car is running.
    This causes it to think that the battery is low when it really isn't.
    I would normally say this is the battery itself but you have already put in a new one, so that is not likely to be the cause.

    Continuously charging the battery at 14.9 will shorten it's life.
    And there is something that is not working right that needs to be located and fixed.
     
  13. rjparker

    rjparker Tu Humilde Sirviente

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    He knows the last battery was bad, he knows if the battery is fully charged the voltage goes down, he knows that his aftermarket remote start is pulling 30 ma continuously, he knows his key fob was stored close and he knows he could get it down to 11 ma drain once he finds the remote start. As is, its 50 ma and more with the fob nearby, which over a period of years, shortened the life of the last battery, especially this year when he did not drive it for extended periods. He bought a solar charger and has an easy and effective way to check the results.
     
  14. sam spade 2

    sam spade 2 Senior Member

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    Yes.
    And NONE of that fully explains why it is over-charging with a new battery in place.
    If the 14.9 really is continuous, as in: it does that immediately after the battery is fully charged, then SOMETHING IS WRONG.
     
  15. TWrecks99

    TWrecks99 New Member

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    In standby the current draw from the 12V battery is about 8-10A (no lights, no audio), is that expected? Is there a place I can camp on to the DCDC inverter output to measure drain?

    I still wonder if temperature is a factor, there is some sensor mounted on top the battery hold down bracket which I am guessing is to measure temp to avoid boiling the AGM dry. Since its near freezing here now, probably not an issue but in Texas summer it sure would be. Maybe the charging voltage is tweaked based on temp?

    The funny part of that smart key "battery saving feature" is after 14 days your battery could already be dead.

    Tim
     
  16. TWrecks99

    TWrecks99 New Member

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    No, not out of the woods yet... Let the car run 4 hours yesterday, charge voltage was 14.9V, charge current started high ~8A but dropped off to less than 1A when I shut it off. 18hrs later, I put it into standby and the MFG diagnostic display showed 12.2V... I drove it 45min to the office charging at 14.9V and left it off. 4hrs later in standby the MFD diagnostic showed 12.2V.

    Drove it 45min back home, stopped for gas near the house. When I restarted it, the lights seemed dim and ABS, TCS and Brake warning lights stayed on. Drove it the 1/2 mile home that way. Left it running and checked the battery voltage, still 14.9V. Stopped the car, waited a min, restarted all seems fine. No codes. Shut it off.

    Checked the battery terminals, chassis bolt back on tight. Negative terminal bolt tight. Positive turned more easily than I expected, I gave a turn or so but the clamp jaws were getting close to meeting so I stopped. After having the dome lights on 5 min the battery measured 12.52V with a DVM.

    Tim
     
  17. cnc97

    cnc97 Senior Member

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    Your battery voltage seems to be ok, but what is the actual charge percentage when load tested. Back before Thanksgiving when I was going thru the same thing, a load test at two different places showed a 82 and 84 percent charge. The major chain parts stores won’t “normally” test a hybrid 12v while installed, but maybe a repair shop other then the dealer will.
     
  18. cnc97

    cnc97 Senior Member

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    This was ign on, brake pump on before going to ready. After ready, 13.95 on the voltage.
     

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  19. sam spade 2

    sam spade 2 Senior Member

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    That is the ONLY way to see the actual battery voltage.
    The MFD display is always low by several tenths.....and tenths are important.

    When the car is "running", you aren't seeing the actual battery voltage but the CHARGING VOLTAGE and 14.9 is too high for continuous operation. Way too high. Something is wrong and needs to be fixed.

    I think this is about the third time I've said that.
    Now I'm done.
     
  20. TWrecks99

    TWrecks99 New Member

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    What app is that from? Torque doesn't show state-of-charge as a sensor that I can see...