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Can I recharge my 12V battery?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by sherlockcrypto, Jan 20, 2022.

  1. sherlockcrypto

    sherlockcrypto Junior Member

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    So silly me left the map light on over the weekend and my prius will not start. Seems like a dead 12V battery. My multi meter is showing .06V between the 2 battery terminals. Is it possible to get one of those battery recharger kits from Amazon and recharge the car battery from my home AC outlet?
     
  2. JC91006

    JC91006 Senior Member

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    if the battery is original from 2015, I would just change it. You should change them every 6 years or so
     
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  3. Wooward

    Wooward Junior Member

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    It’s possible to recover but not guaranteed. 0.06V is very low and may be toast. Are you sure you are measuring DC voltage and not AC voltage? Just want to double check. Either way, if you get a battery charger make sure you get one with a reconditioning function if you’re trying to save it.

    Also, disconnect the battery from your vehicle before you charge it.
     
  4. JC91006

    JC91006 Senior Member

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    Probably won't be able to get any charger to recognize it's a 12v battery when it's measuring .06v
     
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  5. Wooward

    Wooward Junior Member

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    That is true for some chargers. My INC-700a will attempt to do it.


    iPhone ?
     
  6. jzchen

    jzchen Newbie!

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    0.06 V is dead, unless it is a LiFePO4 in protection mode.

    REVVL V+ 5G ?
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Is that even possible? Misreading it, say reading wrong scale? Try another meter first?
     
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  8. sam spade 2

    sam spade 2 Senior Member

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    Absolutely NOT necessary.
    What makes you think that it IS ??
     
  9. sam spade 2

    sam spade 2 Senior Member

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    What exactly do you mean by a "battery recharger KIT" ??

    As others have said, you first need to be sure you are doing the voltage measurement right.

    Then if it IS less than 1 VDC, then you might as well just get a new battery.

    Having a small, smart, tender type charger is a good idea though, just in general, because if you had caught your mistake sooner
    a charge might have gotten you back on the road.
     
  10. PosauneGuy

    PosauneGuy Member

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    I just did the same thing recently. (Actually, my kid left the courtesy lights on inside the cabin overnight.) My battery measured 9 volts in the morning when I couldn't get the car started. Went out to home improvement store and got a trickle charger and hooked it up overnight. Started right up the next day.
     
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  11. JC91006

    JC91006 Senior Member

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    Recovering from 9v is not as difficult as trying to recover from nearly 0v. But you should still monitor your battery as it may have been damaged during your discharge episode. Make sure the battery holds charge and won't get you stranded
     
  12. sam spade 2

    sam spade 2 Senior Member

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    If it really was a smart, automatic tender type charger that you got.......
    PLEASE don't call it a trickle charger. That is NOT the same thing.
     
  13. Wooward

    Wooward Junior Member

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    If his battery is really dead, then as the reconditioner cycles through it’s various voltages the car may turn on/off or even attempt to run at low voltages it’s not rated for. Unless you know the exact charging profile of your charger, I wouldn’t risk it. Is it needed normally, no? But I wouldn’t risk blowing any electronics in my car.


    iPhone ?
     
  14. sherlockcrypto

    sherlockcrypto Junior Member

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    update guys, so i received the charger today from amazon and realized that i was measuring the voltage wrong on my battery. apparently my car battery was at 6.85V, which is about 50% from the 12V required...

    I used this charger from amzn since it was pretty cheap around $30. upload_2022-1-20_23-18-58.png

    I have charged it for about 8 hrs so far, but it is still charging and the charger still shows 40% active. I removed the charger and tested voltage which was showing 12.8V. This confusing to me... i will leave it on overnight and see what happens. Hopefully this prolongs my car battery and i wonder how long i can keep doing this until it stops working?
    upload_2022-1-20_23-22-53.png
     
    #14 sherlockcrypto, Jan 21, 2022
    Last edited: Jan 21, 2022
  15. sherlockcrypto

    sherlockcrypto Junior Member

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    yes you were right. i was using my multimeter wrong. the correct reading was 6.85V before i started charging.
     
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  16. Wooward

    Wooward Junior Member

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    12VDC batteries usually consist of 6 cells with nominal voltage of 2.1VDC. 12.6VDC and above is good. If you can’t get above 10.5VDC, you may have a dead cell or too much lead sulfate built up. This is a pretty good article explaining the science. Best of luck reviving that battery

    Battery Basics - Progressive Dynamics


    iPhone ?
     
  17. Wooward

    Wooward Junior Member

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    Also, it sounds like your charger is currently supplying 12.8VDC to the battery. You won’t know the actual battery voltage of your battery until the charger finishes or you disconnect and use your multimeter.


    iPhone ?
     
  18. meeder

    meeder Active Member

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    It needs to get to 14.4V on the charger but if it can't reach that you will probably have a dead cell.
     
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  19. sherlockcrypto

    sherlockcrypto Junior Member

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    my charger is currently showing 13.7V. also, not sure if relevant, but i am noticing that the amps have decreased... when i first started charging it was at 7A but now its down to 2A as the voltage has increased.
     
  20. jzchen

    jzchen Newbie!

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    Toyota says to replace if the voltage ever goes below 11.0 V, (or was it 10.0 V)? Even at 7.0 V if you took it to a dealer they would recommend replacement.

    You may be able to get the voltage up with a phenomenon called "surface charge". Official testing instructions say to turn on the high beams for 30 seconds (engine off) to remove this superficial energy and measure the voltage in testing. Then compare with the referenced voltage noted above. Since it sat while waiting for the charger I have low expectations you're going to be able to revive it, but I'll keep my fingers crossed as the saying goes...

    REVVL V+ 5G ?