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Help interpreting battery readings

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Gino Veltri, Oct 8, 2021.

  1. Gino Veltri

    Gino Veltri Member

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    So i finally got an OBD2 scanner that works with Dr.Prius, and the results are troubling...i think. A little background: 2005 Gen 2 prius with 196,000 miles. This car came with a bad battery pack and the one in it has had bad cells replaced about 2 years ago and it made it half way across the country. This is my daily driver and has literally been thru hell and back. Ive killed quite a few 12 volts by hooking up way too large sound systems and solar panels and other gadgets but as far as i know the one in there is good...Was told i should change the spark plugs when i bought it 3 years ago, never did. Suspension is a little "iffy" since i got the car with rear driverside damage...

    As of late its been throwing a the red triangle and P3000 and P0A80 and MFD goes down to one bar (which it's never done before) but usually only during the first few min of driving. Then i read a post that suggested i check the fan connections for corrosion and sure enough it was. After cleaning them and resetting the battery, all lights went off and back to normal. I thought i had solved the problem. FFW a few weeks and the codes reappear. Recently reappeared with an O2 sensor code as well, probably unrelated. So my guess is ive got some bad cells but im having trouble understanding the results. Which cells are bad? Why is the HV battery charging to above 250 volts? Also, theres a considerable exhaust smell that starts when the engine kicks up a notch to try and recharge the battery from the one bar state on MFD, It's a very noticeably more toxic smell than usual and it stops when the engine stops charging. Doesnt bother me but might indicate a specific direction to look towards. Honestly Im afraid of whats under the hood as my only experience there has been jumping the 12 volt and changing the oil.

    So does anyone see an obvious culprit? Or do i need to do some more driving, maybe trip the codes again, and take some pics of battery under load? Please check out my picture of dr prius and let me know what seems abnormal please and thank you.
     

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    #1 Gino Veltri, Oct 8, 2021
  2. bisco

    bisco cookie crumbler

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    are you reading the block voltages under load?
     
    #2 bisco, Oct 8, 2021
  3. Gino Veltri

    Gino Veltri Member

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    No, this was just idling after taking the battery out and cleaning it and putting it back in. Im want to drive it a bit but i was concerned about that 252 volts flashing red in the corner. That kinda worried me knowing the HV battery is supposed to be 201 v total.....

    Also just noticed my gif doesnt play as a gif here....
    is a link to the video, again this isnt while driving this is just after putting the HV battery back in and startng the car to try my newest, and working, OBD2 scanner.
     

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    #3 Gino Veltri, Oct 9, 2021
    Last edited: Oct 9, 2021
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    Don't worry too much about the overall pack voltage. It can briefly go "in the red" during charge or discharge. What you should look at is the voltage difference between the highest and lowest blocks during driving (high amps charge and discharge). The battery ecu will set the P0A80 when that difference is too high for too long.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Oct 9, 2021
    bisco likes this.
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    One problem you have is that you're looking at the battery while it's being charged at 14 amps. That hides a lot of information that can be used to ID a bad block.
    Not only that, but it looks to me like all the IR values went to the 19milliohm default value, so that info is also useless right now.

    The easiest way for you to spot a problem would be to let the car sit (at least) overnight, then take the battery voltage readings with the car not in READY. Just keep your foot off the brake and press the power button 2 times. This will be IG-ON mode and you will be able to look at block voltages after the battery has been sitting. It should be more obvious if one or more has a self discharge problem.

    Think of it as having 14 milk jugs and one has a pin hole leak. You're looking at the level of milk in the jug to see if you can spot the leak. Can you spot the leak if someone is continually filling the jugs? or would it be easier to let those jugs sit, untouched for a few hours, and then look at the levels? The info you have above shows the engine is filling the modules continuously while you're trying to find a leak.
     
    #5 TMR-JWAP, Oct 9, 2021
    burrito likes this.
  6. Gino Veltri

    Gino Veltri Member

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    Thanks! this is what i needed to know.
     
    #6 Gino Veltri, Oct 10, 2021
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