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Thread: 12v voltage protection confusion!

  1. #1
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    12v voltage protection confusion!

    Hi All,


    im confused with all the reading i do a 12v battery 11.8v is 0v (dead) and 12v is 80% discharged and you dont really want to discharge past 40-50% so 12.2v so how does this item do anything ? where is the protection ?

    https://www.ebay.com.au/itm/PROJECTA...72.m2749.l2649
    SPECIFICATIONS
    DISCONNECT VOLTAGE 11.6V
    RECONNECT VOLTAGE 12.5V

    Thanks in advance

  2. #2
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    Was going to post a SOC chart but the forum doesn’t allow me to.

    100% is 12.7 volts
    60% is 12.2 volts
    30% is 11.75 volts
    0% is 10.5 volts

  3. #3
    Forum Fixer OffRoadDave's Avatar
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    Quote Originally Posted by money_killer View Post
    Hi All,


    im confused with all the reading i do a 12v battery 11.8v is 0v (dead) and 12v is 80% discharged and you dont really want to discharge past 40-50% so 12.2v so how does this item do anything ? where is the protection ?

    SPECIFICATIONS
    DISCONNECT VOLTAGE 11.6V
    RECONNECT VOLTAGE 12.5V

    Thanks in advance
    The voltages they specify in a "state of charge" chart are open circuit voltages with no load attached in a settled battery, ie. no load connected to it for several hours, this obviously is impractical to actually test for.

    In my opinion there's nothing wrong with a disconnect at 11.6 for a fridge, check the battery within 5 minutes of it turning off and the voltage will likely be back above 12v anyway.
    Cheers Dave

    My farm ute

  4. #4
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    Quote Originally Posted by OffRoadDave View Post
    The voltages they specify in a "state of charge" chart are open circuit voltages with no load attached in a settled battery, ie. no load connected to it for several hours, this obviously is impractical to actually test for.
    And that is why you always test whilst under load. Simple really.

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  6. #6
    Forum Fixer OffRoadDave's Avatar
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    Quote Originally Posted by Tink View Post
    And that is why you always test whilst under load. Simple really.
    Not really, loads vary, and a batteries given AH rating and voltage curve also varies depending on the current being supplied. Essentially if you go by the SOC chart you will be pretty darn safe, but you will not be getting the full benefit of the battery either.
    Cheers Dave

    My farm ute

  7. #7
    Crossed-Over greig's Avatar
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    Quote Originally Posted by Tink View Post
    And that is why you always test whilst under load. Simple really.
    I never test under load. As said, too many variables to get a reliable answer.
    It only takes 10 secs or so for the voltage to stabilise after say running a fridge to get a pretty reliable no load reading.
    Running a battery down to approx 12V (no load ) will give you good use out of it's capacity while also giving you a good life out of the battery.
    Last edited by greig; 14-01-19 at 12:03 AM.

  8. #8
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    Wow, so many experts on here.
    Last edited by pacs; 14-01-19 at 10:21 AM. Reason: sanitized

  9. #9
    Forum Fixer OffRoadDave's Avatar
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    All I was doing was discussing the subject, there was no malice behind it Tink, if you get your nose out of joint that easily, maybe the internet is not for you.
    Cheers Dave

    My farm ute

  10. #10
    Crossed-Over greig's Avatar
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    Quote Originally Posted by Tink View Post
    Wow, so many experts on here. Guess you are all trade qualified auto electricians as well. I will remember to stay away. Not sure why I came back.
    After implying I may have told you what to do, I changed my reply to say "I" never test under load.......

    It's a shame you didn't impart your knowledge and tell us why you would even think of testing under load ??

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