Need help :/

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Ramūnas, Nov 23, 2023.

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  1. Ramūnas

    Ramūnas Junior Member

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    Hello, I was wondering if someone could help me with one problem. My 2005 recently had head gasket replacement, while it was waiting for parts th 12v battery died. When the mechanic brought it back to life the HV battery was completely discharged. He managed to charge it somehow but now the car is in some sort of block. No errors, no dtcs. It used to charge pretty quickly and the charge would hold normaly but now only 3-4 bars. Also I noticed that when I was standing in traffic or somewhere for longer if the battery dropped 3-4 bars it would start to charge it but now it doesn't. Like I said it feel like it's in some sort of protection mode. Could it be the weak 12v batteries fault or should I start looking for a HV battery? Maybe something else. Have a screenshot of Dr Prius while driving if that's of any help. Thank you in advance.
     

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    #1 Ramūnas, Nov 23, 2023
  2. bisco

    bisco cookie crumbler

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    typically, in stop and go traffic, it should drop to two bars and then charge to 3.

    more importantly, how does it drive, and how is fuel consumption? it wouldn't surprise me if you'll need a new battery in the near future.
     
    #2 bisco, Nov 23, 2023
  3. pasadena_commut

    pasadena_commut Senior Member

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    The Dr. Prius bar graphs look OK to me. In particular the resistance values are all pretty close together, which you wouldn't expect if one of the modules was really in bad shape. The resistance values are not very high either, it is 19.0 on a brand new one. On our new pack the maximum delta voltage between modules was .07V, but the slightly larger values you show seem reasonable for an older battery.

    Check the 12V with a voltmeter after the car has been off for a while (at the jump post in the fuse box under the hood for the positive lead, use one of the shiny metal bolt heads on the inverter for the negative.) If the 12V is in really bad shape the car can do odd things. Bad shape would be <12V and/or discharging rapidly with only the low background load (some electronics stay on when the car is off - be sure all doors and hatch are closed). That said, as long as the little battery stays above 12V it should work well enough because this car really only uses it to start the computers and runs off the power from the inverter the rest of the time.

    Since there was work done under the hood I would have suggested that maybe some cable wasn't reconnected, but hard to imagine that not immediately throwing a code.

    If the 12V isn't overtly failed try unplugging it at the ground post, wait at least a minute, then reattach it. That should clear most of the information the car has stored. Then drive it around for a while and see if it will charge up normally. If you can get the car to the top of a reasonably high hill and then descend with your foot slightly on the brake to increase regen does it charge all the way up? In my local area there is height difference of about 133 meters between my home and my former work place, and when just driving home normally that was usually enough to have the pack fully charged when I reached home.
     
    #3 pasadena_commut, Nov 23, 2023
  4. dolj

    dolj Senior Member

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    Any error lights on the dash? If yes, then you have DTCs. If you do not see DTCs, it means your code reader is not good enough. A good code reader should see 11-14 ECUs and be able to pull codes from all of them.
    Adding to this, "bad shape" would also be the battery voltage dropping quickly to under 10.5 V in a very short period of time.
     
    #4 dolj, Nov 23, 2023
  5. Ramūnas

    Ramūnas Junior Member

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    Well I don't have any dtcs on dash or in obd. As for fuel consumption, it does take a little bit more, maybe 0.5 l/100km more. I think I will change the 12v first and then see if anything changes. Also for the resistance difference I can see that some times 4 or 5 of them are like 1 ohm less than others just in this screenshot I didn't capture it.
     
    #5 Ramūnas, Nov 24, 2023
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    I have always found that if I lose 12V power to my car, then the HV battery gauge and hybrid operation are "abnormal" for a few days (up to a week).

    I assume that various ecu's need time and use to "relearn" operational values.

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Nov 24, 2023
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